[libcxx] [llvm] Add C++23 stacktrace (P0881R7) (PR #136528)

Steve O'Brien via llvm-commits llvm-commits at lists.llvm.org
Mon Apr 21 16:28:10 PDT 2025


https://github.com/elsteveogrande updated https://github.com/llvm/llvm-project/pull/136528

>From 2f19f457a6f609e71b6d2da9e75dd76234f910a5 Mon Sep 17 00:00:00 2001
From: Steve O'Brien <steve at obrien.cc>
Date: Thu, 16 Jan 2025 18:32:09 -0500
Subject: [PATCH 1/4] Add C++23 stacktrace

---
 libcxx/CMakeLists.txt                         |   6 +
 libcxx/docs/UserDocumentation.rst             |   1 +
 libcxx/docs/VendorDocumentation.rst           |   8 +
 libcxx/include/CMakeLists.txt                 |   7 +
 libcxx/include/__config                       |  27 ++
 libcxx/include/__config_site.in               |   1 +
 libcxx/include/__ostream/basic_ostream.h      |   2 +-
 .../__stacktrace/basic_stacktrace.h           | 306 +++++++++++++++++
 .../experimental/__stacktrace/detail/alloc.h  | 103 ++++++
 .../__stacktrace/detail/context.h             |  53 +++
 .../experimental/__stacktrace/detail/entry.h  |  44 +++
 .../__stacktrace/detail/to_string.h           |  46 +++
 .../__stacktrace/stacktrace_entry.h           | 111 ++++++
 libcxx/include/experimental/stacktrace        | 191 +++++++++++
 libcxx/include/module.modulemap.in            |  10 +
 libcxx/modules/std/stacktrace.inc             |   7 +-
 libcxx/src/CMakeLists.txt                     |  19 ++
 libcxx/src/experimental/stacktrace/alloc.cpp  |  20 ++
 .../experimental/stacktrace/common/config.h   |  41 +++
 .../experimental/stacktrace/common/debug.cpp  |  19 ++
 .../experimental/stacktrace/common/debug.h    |  55 +++
 .../experimental/stacktrace/common/failed.h   |  29 ++
 .../src/experimental/stacktrace/common/fd.cpp |  31 ++
 .../src/experimental/stacktrace/common/fd.h   | 122 +++++++
 .../experimental/stacktrace/common/images.h   |  33 ++
 .../src/experimental/stacktrace/context.cpp   | 104 ++++++
 .../src/experimental/stacktrace/linux/elf.h   | 315 ++++++++++++++++++
 .../stacktrace/linux/linux-dl.cpp             |  58 ++++
 .../stacktrace/linux/linux-elf.cpp            |  53 +++
 .../stacktrace/linux/linux-sym.cpp            |  61 ++++
 .../src/experimental/stacktrace/linux/linux.h |  98 ++++++
 .../src/experimental/stacktrace/osx/osx.cpp   | 111 ++++++
 libcxx/src/experimental/stacktrace/osx/osx.h  |  31 ++
 .../experimental/stacktrace/stacktrace.cpp    |  94 ++++++
 .../stacktrace/tools/addr2line.cpp            | 100 ++++++
 .../experimental/stacktrace/tools/atos.cpp    | 115 +++++++
 .../stacktrace/tools/llvm_symbolizer.cpp      | 112 +++++++
 .../experimental/stacktrace/tools/pspawn.h    | 163 +++++++++
 .../src/experimental/stacktrace/tools/tools.h |  65 ++++
 .../stacktrace/tools/toolspawner.cpp          | 185 ++++++++++
 .../experimental/stacktrace/unwind/unwind.cpp |  60 ++++
 .../experimental/stacktrace/unwind/unwind.h   |  30 ++
 .../stacktrace/windows/dbghelp_dll.cpp        |  56 ++++
 .../stacktrace/windows/dbghelp_dll.h          |  71 ++++
 .../experimental/stacktrace/windows/dll.cpp   |  40 +++
 .../src/experimental/stacktrace/windows/dll.h |  68 ++++
 .../stacktrace/windows/psapi_dll.cpp          |  48 +++
 .../stacktrace/windows/psapi_dll.h            |  55 +++
 .../stacktrace/windows/win_impl.cpp           | 204 ++++++++++++
 .../stacktrace/windows/win_impl.h             |  38 +++
 .../stacktrace/simple.o0.nodebug.pass.cpp     |  32 ++
 .../stacktrace/simple.o0.nosplit.pass.cpp     |  29 ++
 .../stacktrace/simple.o0.split.pass.cpp       |  29 ++
 .../stacktrace/simple.o3.nodebug.pass.cpp     |  32 ++
 .../stacktrace/simple.o3.nosplit.pass.cpp     |  29 ++
 .../stacktrace/simple.o3.split.pass.cpp       |  29 ++
 .../test/libcxx/transitive_includes/cxx03.csv |   5 +
 .../test/libcxx/transitive_includes/cxx11.csv |   5 +
 .../test/libcxx/transitive_includes/cxx14.csv |   5 +
 .../test/libcxx/transitive_includes/cxx17.csv |   5 +
 .../test/libcxx/transitive_includes/cxx23.csv |  29 ++
 .../test/libcxx/transitive_includes/cxx26.csv |  29 ++
 .../diagnostics/stacktrace/basic.cmp.pass.cpp | 106 ++++++
 .../stacktrace/basic.cons.pass.cpp            | 308 +++++++++++++++++
 .../stacktrace/basic.hash.pass.cpp            |  44 +++
 .../diagnostics/stacktrace/basic.mod.pass.cpp |  40 +++
 .../stacktrace/basic.nonmem.pass.cpp          |  91 +++++
 .../diagnostics/stacktrace/basic.obs.pass.cpp | 156 +++++++++
 .../std/diagnostics/stacktrace/basic.pass.cpp | 154 +++++++++
 .../diagnostics/stacktrace/entry.cmp.pass.cpp |  65 ++++
 .../stacktrace/entry.cons.pass.cpp            |  63 ++++
 .../diagnostics/stacktrace/entry.obs.pass.cpp |  51 +++
 .../std/diagnostics/stacktrace/entry.pass.cpp |  66 ++++
 .../stacktrace/entry.query.pass.cpp           |  85 +++++
 .../diagnostics/stacktrace/format.pass.cpp    |  53 +++
 .../std/diagnostics/stacktrace/syn.pass.cpp   | 147 ++++++++
 libcxx/utils/libcxx/header_information.py     |   4 +-
 llvm/utils/gn/secondary/libcxx/src/BUILD.gn   |  34 ++
 78 files changed, 5348 insertions(+), 4 deletions(-)
 create mode 100644 libcxx/include/experimental/__stacktrace/basic_stacktrace.h
 create mode 100644 libcxx/include/experimental/__stacktrace/detail/alloc.h
 create mode 100644 libcxx/include/experimental/__stacktrace/detail/context.h
 create mode 100644 libcxx/include/experimental/__stacktrace/detail/entry.h
 create mode 100644 libcxx/include/experimental/__stacktrace/detail/to_string.h
 create mode 100644 libcxx/include/experimental/__stacktrace/stacktrace_entry.h
 create mode 100644 libcxx/include/experimental/stacktrace
 create mode 100644 libcxx/src/experimental/stacktrace/alloc.cpp
 create mode 100644 libcxx/src/experimental/stacktrace/common/config.h
 create mode 100644 libcxx/src/experimental/stacktrace/common/debug.cpp
 create mode 100644 libcxx/src/experimental/stacktrace/common/debug.h
 create mode 100644 libcxx/src/experimental/stacktrace/common/failed.h
 create mode 100644 libcxx/src/experimental/stacktrace/common/fd.cpp
 create mode 100644 libcxx/src/experimental/stacktrace/common/fd.h
 create mode 100644 libcxx/src/experimental/stacktrace/common/images.h
 create mode 100644 libcxx/src/experimental/stacktrace/context.cpp
 create mode 100644 libcxx/src/experimental/stacktrace/linux/elf.h
 create mode 100644 libcxx/src/experimental/stacktrace/linux/linux-dl.cpp
 create mode 100644 libcxx/src/experimental/stacktrace/linux/linux-elf.cpp
 create mode 100644 libcxx/src/experimental/stacktrace/linux/linux-sym.cpp
 create mode 100644 libcxx/src/experimental/stacktrace/linux/linux.h
 create mode 100644 libcxx/src/experimental/stacktrace/osx/osx.cpp
 create mode 100644 libcxx/src/experimental/stacktrace/osx/osx.h
 create mode 100644 libcxx/src/experimental/stacktrace/stacktrace.cpp
 create mode 100644 libcxx/src/experimental/stacktrace/tools/addr2line.cpp
 create mode 100644 libcxx/src/experimental/stacktrace/tools/atos.cpp
 create mode 100644 libcxx/src/experimental/stacktrace/tools/llvm_symbolizer.cpp
 create mode 100644 libcxx/src/experimental/stacktrace/tools/pspawn.h
 create mode 100644 libcxx/src/experimental/stacktrace/tools/tools.h
 create mode 100644 libcxx/src/experimental/stacktrace/tools/toolspawner.cpp
 create mode 100644 libcxx/src/experimental/stacktrace/unwind/unwind.cpp
 create mode 100644 libcxx/src/experimental/stacktrace/unwind/unwind.h
 create mode 100644 libcxx/src/experimental/stacktrace/windows/dbghelp_dll.cpp
 create mode 100644 libcxx/src/experimental/stacktrace/windows/dbghelp_dll.h
 create mode 100644 libcxx/src/experimental/stacktrace/windows/dll.cpp
 create mode 100644 libcxx/src/experimental/stacktrace/windows/dll.h
 create mode 100644 libcxx/src/experimental/stacktrace/windows/psapi_dll.cpp
 create mode 100644 libcxx/src/experimental/stacktrace/windows/psapi_dll.h
 create mode 100644 libcxx/src/experimental/stacktrace/windows/win_impl.cpp
 create mode 100644 libcxx/src/experimental/stacktrace/windows/win_impl.h
 create mode 100644 libcxx/test/libcxx/stacktrace/simple.o0.nodebug.pass.cpp
 create mode 100644 libcxx/test/libcxx/stacktrace/simple.o0.nosplit.pass.cpp
 create mode 100644 libcxx/test/libcxx/stacktrace/simple.o0.split.pass.cpp
 create mode 100644 libcxx/test/libcxx/stacktrace/simple.o3.nodebug.pass.cpp
 create mode 100644 libcxx/test/libcxx/stacktrace/simple.o3.nosplit.pass.cpp
 create mode 100644 libcxx/test/libcxx/stacktrace/simple.o3.split.pass.cpp
 create mode 100644 libcxx/test/std/diagnostics/stacktrace/basic.cmp.pass.cpp
 create mode 100644 libcxx/test/std/diagnostics/stacktrace/basic.cons.pass.cpp
 create mode 100644 libcxx/test/std/diagnostics/stacktrace/basic.hash.pass.cpp
 create mode 100644 libcxx/test/std/diagnostics/stacktrace/basic.mod.pass.cpp
 create mode 100644 libcxx/test/std/diagnostics/stacktrace/basic.nonmem.pass.cpp
 create mode 100644 libcxx/test/std/diagnostics/stacktrace/basic.obs.pass.cpp
 create mode 100644 libcxx/test/std/diagnostics/stacktrace/basic.pass.cpp
 create mode 100644 libcxx/test/std/diagnostics/stacktrace/entry.cmp.pass.cpp
 create mode 100644 libcxx/test/std/diagnostics/stacktrace/entry.cons.pass.cpp
 create mode 100644 libcxx/test/std/diagnostics/stacktrace/entry.obs.pass.cpp
 create mode 100644 libcxx/test/std/diagnostics/stacktrace/entry.pass.cpp
 create mode 100644 libcxx/test/std/diagnostics/stacktrace/entry.query.pass.cpp
 create mode 100644 libcxx/test/std/diagnostics/stacktrace/format.pass.cpp
 create mode 100644 libcxx/test/std/diagnostics/stacktrace/syn.pass.cpp

diff --git a/libcxx/CMakeLists.txt b/libcxx/CMakeLists.txt
index ebaa6e9fd0e97..b12bf2ead76e5 100644
--- a/libcxx/CMakeLists.txt
+++ b/libcxx/CMakeLists.txt
@@ -131,6 +131,11 @@ option(LIBCXX_ENABLE_VENDOR_AVAILABILITY_ANNOTATIONS
    the shared library they shipped should turn this on and see `include/__configuration/availability.h`
    for more details." OFF)
 
+option(LIBCPP_STACKTRACE_ALLOW_TOOLS_AT_RUNTIME
+   "For C++23 <stacktrace>: whether to allow invocation of `addr2line`, `llvm-addr2line` or `atos`
+   at runtime (if it's available in PATH) to resolve call-chain addresses in the stacktrace
+   into source locations, if other methods are not available." ON)
+
 if (CMAKE_CXX_COMPILER_ID STREQUAL "GNU")
   set(LIBCXX_DEFAULT_TEST_CONFIG "llvm-libc++-shared-gcc.cfg.in")
 elseif(MINGW)
@@ -757,6 +762,7 @@ config_define(${LIBCXX_ENABLE_UNICODE} _LIBCPP_HAS_UNICODE)
 config_define(${LIBCXX_ENABLE_WIDE_CHARACTERS} _LIBCPP_HAS_WIDE_CHARACTERS)
 config_define(${LIBCXX_ENABLE_TIME_ZONE_DATABASE} _LIBCPP_HAS_TIME_ZONE_DATABASE)
 config_define(${LIBCXX_ENABLE_VENDOR_AVAILABILITY_ANNOTATIONS} _LIBCPP_HAS_VENDOR_AVAILABILITY_ANNOTATIONS)
+config_define(${LIBCPP_STACKTRACE_ALLOW_TOOLS_AT_RUNTIME} _LIBCPP_STACKTRACE_ALLOW_TOOLS_AT_RUNTIME)
 
 # TODO: Remove in LLVM 21. We're leaving an error to make this fail explicitly.
 if (LIBCXX_ENABLE_ASSERTIONS)
diff --git a/libcxx/docs/UserDocumentation.rst b/libcxx/docs/UserDocumentation.rst
index 4a11a10224ae9..649b7551eb746 100644
--- a/libcxx/docs/UserDocumentation.rst
+++ b/libcxx/docs/UserDocumentation.rst
@@ -70,6 +70,7 @@ when ``-fexperimental-library`` is passed:
 
 * The parallel algorithms library (``<execution>`` and the associated algorithms)
 * ``std::chrono::tzdb`` and related time zone functionality
+* ``<stacktrace>``
 * ``<syncstream>``
 
 .. note::
diff --git a/libcxx/docs/VendorDocumentation.rst b/libcxx/docs/VendorDocumentation.rst
index 959a28607d75d..b05d494db4f9b 100644
--- a/libcxx/docs/VendorDocumentation.rst
+++ b/libcxx/docs/VendorDocumentation.rst
@@ -185,6 +185,14 @@ General purpose options
    ship the IANA time zone database. When time zones are not supported,
    time zone support in <chrono> will be disabled.
 
+.. option:: LIBCPP_STACKTRACE_ALLOW_TOOLS_AT_RUNTIME:BOOL
+
+   **Default**: ``OFF``
+
+   For C++23 <stacktrace>: whether to allow invocation of ``addr2line`` or ``llvm-addr2line``
+   at runtime (if it's available in PATH) to resolve call-chain addresses in the stacktrace
+   into source locations, if other methods are not available.
+
 .. option:: LIBCXX_INSTALL_LIBRARY_DIR:PATH
 
   **Default**: ``lib${LIBCXX_LIBDIR_SUFFIX}``
diff --git a/libcxx/include/CMakeLists.txt b/libcxx/include/CMakeLists.txt
index f1bdf684a8549..ef091e40b9ec8 100644
--- a/libcxx/include/CMakeLists.txt
+++ b/libcxx/include/CMakeLists.txt
@@ -991,10 +991,17 @@ set(files
   experimental/__simd/traits.h
   experimental/__simd/utility.h
   experimental/__simd/vec_ext.h
+  experimental/__stacktrace/basic_stacktrace.h
+  experimental/__stacktrace/detail/alloc.h
+  experimental/__stacktrace/detail/context.h
+  experimental/__stacktrace/detail/entry.h
+  experimental/__stacktrace/detail/to_string.h
+  experimental/__stacktrace/stacktrace_entry.h
   experimental/iterator
   experimental/memory
   experimental/propagate_const
   experimental/simd
+  experimental/stacktrace
   experimental/type_traits
   experimental/utility
   ext/__hash
diff --git a/libcxx/include/__config b/libcxx/include/__config
index e14632f65b877..071961cf73438 100644
--- a/libcxx/include/__config
+++ b/libcxx/include/__config
@@ -977,6 +977,33 @@ typedef __char32_t char32_t;
 #    define _LIBCPP_NOINLINE
 #  endif
 
+// Some functions, e.g. std::stacktrace::current, need to avoid being
+// tail-called by (and tail-calling other) functions, for proper enumeration of
+// call-stack frames.
+// clang-format off
+
+// Disables tail-call optimization for "outbound" calls
+// performed in the function annotated with this attribute.
+#  if __has_cpp_attribute(_Clang::__disable_tail_calls__)
+#    define _LIBCPP_NO_TAIL_CALLS_OUT [[_Clang::__disable_tail_calls__]]
+#  elif __has_cpp_attribute(__gnu__::__optimize__)
+#    define _LIBCPP_NO_TAIL_CALLS_OUT [[__gnu__::__optimize__("no-optimize-sibling-calls")]]
+#  else
+#    define _LIBCPP_NO_TAIL_CALLS_OUT
+#  endif
+
+// Disables tail-call optimization for "inbound" calls -- that is,
+// calls from some other function calling the one having this attribute.
+#  if __has_cpp_attribute(_Clang::__not_tail_called__)
+#    define _LIBCPP_NO_TAIL_CALLS_IN [[_Clang::__not_tail_called__]]
+#  else
+#    define _LIBCPP_NO_TAIL_CALLS_IN
+#  endif
+
+// Disable TCO for calls into, and out from, the annotated function.
+#  define _LIBCPP_NO_TAIL_CALLS _LIBCPP_NO_TAIL_CALLS_IN _LIBCPP_NO_TAIL_CALLS_OUT
+// clang-format on
+
 // We often repeat things just for handling wide characters in the library.
 // When wide characters are disabled, it can be useful to have a quick way of
 // disabling it without having to resort to #if-#endif, which has a larger
diff --git a/libcxx/include/__config_site.in b/libcxx/include/__config_site.in
index fc01aaf2d8746..4e25ed040c9d0 100644
--- a/libcxx/include/__config_site.in
+++ b/libcxx/include/__config_site.in
@@ -33,6 +33,7 @@
 #cmakedefine _LIBCPP_HAS_NO_STD_MODULES
 #cmakedefine01 _LIBCPP_HAS_TIME_ZONE_DATABASE
 #cmakedefine01 _LIBCPP_INSTRUMENTED_WITH_ASAN
+#cmakedefine01 _LIBCPP_STACKTRACE_ALLOW_TOOLS_AT_RUNTIME
 
 // PSTL backends
 #cmakedefine _LIBCPP_PSTL_BACKEND_SERIAL
diff --git a/libcxx/include/__ostream/basic_ostream.h b/libcxx/include/__ostream/basic_ostream.h
index f7473a36d8ccc..891dddbf79c42 100644
--- a/libcxx/include/__ostream/basic_ostream.h
+++ b/libcxx/include/__ostream/basic_ostream.h
@@ -570,7 +570,7 @@ _LIBCPP_HIDE_FROM_ABI _Stream&& operator<<(_Stream&& __os, const _Tp& __x) {
 }
 
 template <class _CharT, class _Traits, class _Allocator>
-basic_ostream<_CharT, _Traits>&
+_LIBCPP_HIDE_FROM_ABI basic_ostream<_CharT, _Traits>&
 operator<<(basic_ostream<_CharT, _Traits>& __os, const basic_string<_CharT, _Traits, _Allocator>& __str) {
   return std::__put_character_sequence(__os, __str.data(), __str.size());
 }
diff --git a/libcxx/include/experimental/__stacktrace/basic_stacktrace.h b/libcxx/include/experimental/__stacktrace/basic_stacktrace.h
new file mode 100644
index 0000000000000..8ac1de82b1c63
--- /dev/null
+++ b/libcxx/include/experimental/__stacktrace/basic_stacktrace.h
@@ -0,0 +1,306 @@
+// -*- C++ -*-
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef _LIBCPP_EXPERIMENTAL_BASIC_STACKTRACE
+#define _LIBCPP_EXPERIMENTAL_BASIC_STACKTRACE
+
+#include <experimental/__stacktrace/detail/entry.h>
+#include <experimental/__stacktrace/stacktrace_entry.h>
+
+#include <__config>
+#include <__format/formatter.h>
+#include <__functional/function.h>
+#include <__functional/hash.h>
+#include <__fwd/format.h>
+#include <__fwd/sstream.h>
+#include <__iterator/iterator.h>
+#include <__iterator/iterator_traits.h>
+#include <__iterator/reverse_access.h>
+#include <__iterator/reverse_iterator.h>
+#include <__memory/allocator.h>
+#include <__memory/allocator_traits.h>
+#include <__memory_resource/memory_resource.h>
+#include <__memory_resource/polymorphic_allocator.h>
+#include <__ostream/basic_ostream.h>
+#include <__utility/move.h>
+#include <__vector/pmr.h>
+#include <__vector/swap.h>
+#include <__vector/vector.h>
+#include <cstddef>
+#include <list>
+#include <memory>
+#include <string>
+
+#include <experimental/__stacktrace/detail/alloc.h>
+#include <experimental/__stacktrace/detail/context.h>
+#include <experimental/__stacktrace/detail/to_string.h>
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+// (19.6.4)
+// Class template basic_stacktrace [stacktrace.basic]
+
+class stacktrace_entry;
+
+template <class _Allocator>
+class _LIBCPP_EXPORTED_FROM_ABI basic_stacktrace {
+  friend struct hash<basic_stacktrace<_Allocator>>;
+  friend struct __stacktrace::__to_string;
+
+  using _ATraits _LIBCPP_NODEBUG               = allocator_traits<_Allocator>;
+  constexpr static bool __kPropOnCopy          = _ATraits::propagate_on_container_copy_assignment::value;
+  constexpr static bool __kPropOnMove          = _ATraits::propagate_on_container_move_assignment::value;
+  constexpr static bool __kPropOnSwap          = _ATraits::propagate_on_container_swap::value;
+  constexpr static bool __kAlwaysEqual         = _ATraits::is_always_equal::value;
+  constexpr static bool __kNoThrowDflConstruct = is_nothrow_default_constructible_v<_Allocator>;
+  constexpr static bool __kNoThrowAlloc =
+      noexcept(noexcept(_Allocator().allocate(1)) && noexcept(_Allocator().allocate_at_least(1)));
+
+  using __entry_vec _LIBCPP_NODEBUG = vector<stacktrace_entry, _Allocator>;
+
+  [[no_unique_address]] _Allocator __alloc_;
+  __entry_vec __entries_;
+
+  _LIBCPP_HIDE_FROM_ABI basic_stacktrace(const _Allocator& __alloc, std::pmr::list<__stacktrace::entry>&& __vec)
+      : __alloc_(__alloc), __entries_(__alloc) {
+    __entries_.reserve(__vec.size());
+    for (auto& __entry : __vec) {
+      __entries_.emplace_back(std::move(__entry));
+    }
+  }
+
+public:
+  // (19.6.4.1)
+  // Overview [stacktrace.basic.overview]
+
+  using value_type      = stacktrace_entry;
+  using const_reference = const value_type&;
+  using reference       = value_type&;
+  using difference_type = ptrdiff_t;
+  using size_type       = size_t;
+  using allocator_type  = _Allocator;
+  using const_iterator  = decltype(__entries_)::const_iterator;
+  using iterator        = const_iterator;
+
+  using reverse_iterator       = std::reverse_iterator<basic_stacktrace::iterator>;
+  using const_reverse_iterator = std::reverse_iterator<basic_stacktrace::const_iterator>;
+
+  // (19.6.4.2)
+  // Creation and assignment [stacktrace.basic.cons]
+
+  _LIBCPP_NO_TAIL_CALLS _LIBCPP_NOINLINE _LIBCPP_EXPORTED_FROM_ABI static basic_stacktrace
+  current(const allocator_type& __caller_alloc = allocator_type()) noexcept(__kNoThrowAlloc) {
+    __stacktrace::alloc __alloc(__caller_alloc);
+    __stacktrace::context __tr{__alloc};
+    __tr.do_stacktrace(1, /* infinite max_depth */ ~0);
+    return {__caller_alloc, std::move(__tr.__entries_)};
+  }
+
+  _LIBCPP_NO_TAIL_CALLS _LIBCPP_NOINLINE _LIBCPP_EXPORTED_FROM_ABI static basic_stacktrace
+  current(size_type __skip, const allocator_type& __caller_alloc = allocator_type()) noexcept(__kNoThrowAlloc) {
+    __stacktrace::alloc __alloc(__caller_alloc);
+    __stacktrace::context __tr{__alloc};
+    __tr.do_stacktrace(__skip + 1, /* infinite max_depth */ ~0);
+    return {__caller_alloc, std::move(__tr.__entries_)};
+  }
+
+  _LIBCPP_NO_TAIL_CALLS _LIBCPP_NOINLINE _LIBCPP_EXPORTED_FROM_ABI static basic_stacktrace
+  current(size_type __skip,
+          size_type __max_depth,
+          const allocator_type& __caller_alloc = allocator_type()) noexcept(__kNoThrowAlloc) {
+    __stacktrace::alloc __alloc(__caller_alloc);
+    __stacktrace::context __tr{__alloc};
+    __tr.do_stacktrace(__skip + 1, __max_depth);
+    return {__caller_alloc, std::move(__tr.__entries_)};
+  }
+
+  _LIBCPP_EXPORTED_FROM_ABI constexpr ~basic_stacktrace() = default;
+
+  _LIBCPP_EXPORTED_FROM_ABI basic_stacktrace() noexcept(__kNoThrowDflConstruct) : basic_stacktrace(allocator_type()) {}
+
+  _LIBCPP_EXPORTED_FROM_ABI explicit basic_stacktrace(const allocator_type& __alloc) noexcept
+      : __alloc_(__alloc), __entries_(__alloc_) {}
+
+  _LIBCPP_EXPORTED_FROM_ABI basic_stacktrace(basic_stacktrace const& __other) = default;
+
+  _LIBCPP_EXPORTED_FROM_ABI basic_stacktrace(basic_stacktrace&& __other) noexcept = default;
+
+  _LIBCPP_EXPORTED_FROM_ABI basic_stacktrace(basic_stacktrace const& __other, allocator_type const& __alloc)
+      : __alloc_(__alloc), __entries_(__other.__entries_, __alloc) {}
+
+  _LIBCPP_EXPORTED_FROM_ABI basic_stacktrace(basic_stacktrace&& __other, allocator_type const& __alloc)
+      : __alloc_(__alloc) {
+    if (__kAlwaysEqual || __alloc_ == __other.__alloc_) {
+      __entries_ = std::move(__other.__entries_);
+    } else {
+      // "moving" from a container with a different allocator; we're forced to copy items instead
+      for (auto const& __entry : __other.__entries_) {
+        __entries_.push_back(__entry);
+      }
+    }
+  }
+
+  _LIBCPP_EXPORTED_FROM_ABI basic_stacktrace& operator=(const basic_stacktrace& __other) {
+    if (this == std::addressof(__other)) {
+      return *this;
+    }
+    if (__kPropOnCopy) {
+      __alloc_ = __other.__alloc_;
+    }
+    __entries_ = {__other.__entries_, __alloc_};
+    return *this;
+  }
+
+  _LIBCPP_EXPORTED_FROM_ABI basic_stacktrace&
+  operator=(basic_stacktrace&& __other) noexcept(__kPropOnMove || __kAlwaysEqual) {
+    if (this == std::addressof(__other)) {
+      return *this;
+    }
+    if (__kPropOnMove) {
+      __alloc_   = __other.__alloc_;
+      __entries_ = std::move(__other.__entries_);
+    } else {
+      auto __allocs_eq = __kAlwaysEqual || __alloc_ == __other.__alloc_;
+      if (__allocs_eq) {
+        __entries_ = std::move(__other.__entries_);
+      } else {
+        // "moving" from a container with a different allocator;
+        // we're forced to copy items instead
+        for (auto const& __entry : __other.__entries_) {
+          __entries_.push_back(__entry);
+        }
+      }
+    }
+    return *this;
+  }
+
+  // clang-format on
+
+  // (19.6.4.3)
+  // [stacktrace.basic.obs], observers
+
+  [[nodiscard]] _LIBCPP_EXPORTED_FROM_ABI allocator_type get_allocator() const noexcept { return __alloc_; }
+
+  [[nodiscard]] _LIBCPP_EXPORTED_FROM_ABI const_iterator begin() const noexcept { return __entries_.begin(); }
+  [[nodiscard]] _LIBCPP_EXPORTED_FROM_ABI const_iterator end() const noexcept { return __entries_.end(); }
+  [[nodiscard]] _LIBCPP_EXPORTED_FROM_ABI const_reverse_iterator rbegin() const noexcept { return __entries_.rbegin(); }
+  [[nodiscard]] _LIBCPP_EXPORTED_FROM_ABI const_reverse_iterator rend() const noexcept { return __entries_.rend(); }
+
+  [[nodiscard]] _LIBCPP_EXPORTED_FROM_ABI const_iterator cbegin() const noexcept { return __entries_.cbegin(); }
+  [[nodiscard]] _LIBCPP_EXPORTED_FROM_ABI const_iterator cend() const noexcept { return __entries_.cend(); }
+  [[nodiscard]] _LIBCPP_EXPORTED_FROM_ABI const_reverse_iterator crbegin() const noexcept {
+    return __entries_.crbegin();
+  }
+  [[nodiscard]] _LIBCPP_EXPORTED_FROM_ABI const_reverse_iterator crend() const noexcept { return __entries_.crend(); }
+
+  [[nodiscard]] _LIBCPP_EXPORTED_FROM_ABI bool empty() const noexcept { return __entries_.empty(); }
+  [[nodiscard]] _LIBCPP_EXPORTED_FROM_ABI size_type size() const noexcept { return __entries_.size(); }
+  [[nodiscard]] _LIBCPP_EXPORTED_FROM_ABI size_type max_size() const noexcept { return __entries_.max_size(); }
+
+  [[nodiscard]] _LIBCPP_EXPORTED_FROM_ABI const_reference operator[](size_type __i) const { return __entries_[__i]; }
+  [[nodiscard]] _LIBCPP_EXPORTED_FROM_ABI const_reference at(size_type __i) const { return __entries_.at(__i); }
+
+  // (19.6.4.4)
+  // [stacktrace.basic.cmp], comparisons
+
+  template <class _Allocator2>
+  _LIBCPP_EXPORTED_FROM_ABI friend bool
+  operator==(const basic_stacktrace& __x, const basic_stacktrace<_Allocator2>& __y) noexcept {
+    if (__x.size() != __y.size()) {
+      return false;
+    }
+    auto __xi = __x.begin();
+    auto __yi = __y.begin();
+    auto __xe = __x.end();
+    while (__xi != __xe) {
+      if (*__xi++ != *__yi++) {
+        return false;
+      }
+    }
+    return true;
+  }
+
+  template <class _Allocator2>
+  _LIBCPP_EXPORTED_FROM_ABI friend strong_ordering
+  operator<=>(const basic_stacktrace& __x, const basic_stacktrace<_Allocator2>& __y) noexcept {
+    auto __ret = __x.size() <=> __y.size();
+    if (__ret != std::strong_ordering::equal) {
+      return __ret;
+    }
+    auto __xi = __x.begin();
+    auto __yi = __y.begin();
+    auto __xe = __x.end();
+    while ((__ret == std::strong_ordering::equal) && __xi != __xe) {
+      __ret = *__xi++ <=> *__yi++;
+    }
+    return __ret;
+  }
+
+  // (19.6.4.5)
+  // [stacktrace.basic.mod], modifiers
+
+  _LIBCPP_EXPORTED_FROM_ABI void swap(basic_stacktrace<_Allocator>& __other) noexcept {
+    std::swap(__entries_, __other.__entries_);
+    if (__kPropOnSwap) {
+      std::swap(__alloc_, __other.__alloc_);
+    }
+  }
+};
+
+using stacktrace = basic_stacktrace<allocator<stacktrace_entry>>;
+
+namespace pmr {
+using stacktrace = basic_stacktrace<polymorphic_allocator<stacktrace_entry>>;
+} // namespace pmr
+
+// (19.6.4.6)
+// Non-member functions [stacktrace.basic.nonmem]
+
+template <class _Allocator>
+_LIBCPP_EXPORTED_FROM_ABI inline void
+swap(basic_stacktrace<_Allocator>& __a, basic_stacktrace<_Allocator>& __b) noexcept(noexcept(__a.swap(__b))) {
+  __a.swap(__b);
+}
+
+template <class _Allocator>
+_LIBCPP_EXPORTED_FROM_ABI inline string to_string(const basic_stacktrace<_Allocator>& __stacktrace) {
+  return __stacktrace::__to_string()(__stacktrace);
+}
+
+template <class _Allocator>
+_LIBCPP_EXPORTED_FROM_ABI inline ostream& operator<<(ostream& __os, const basic_stacktrace<_Allocator>& __stacktrace) {
+  auto __str = __stacktrace::__to_string()(__stacktrace);
+  return __os << __str;
+}
+
+// (19.6.5)
+// Formatting support [stacktrace.format]
+
+// TODO(stacktrace23): needs `formatter`
+template <class _Allocator>
+struct _LIBCPP_EXPORTED_FROM_ABI formatter<basic_stacktrace<_Allocator>>;
+
+// (19.6.6)
+// Hash support [stacktrace.basic.hash]
+
+template <class _Allocator>
+struct _LIBCPP_EXPORTED_FROM_ABI hash<basic_stacktrace<_Allocator>> {
+  [[nodiscard]] size_t operator()(basic_stacktrace<_Allocator> const& __context) const noexcept {
+    size_t __ret = 1;
+    for (auto const& __entry : __context.__entries_) {
+      __ret += hash<uintptr_t>()(__entry.native_handle());
+      __ret *= 3001;
+    }
+    return __ret;
+  }
+};
+
+_LIBCPP_END_NAMESPACE_STD
+
+#endif // _LIBCPP_EXPERIMENTAL_BASIC_STACKTRACE
diff --git a/libcxx/include/experimental/__stacktrace/detail/alloc.h b/libcxx/include/experimental/__stacktrace/detail/alloc.h
new file mode 100644
index 0000000000000..a0949b5751899
--- /dev/null
+++ b/libcxx/include/experimental/__stacktrace/detail/alloc.h
@@ -0,0 +1,103 @@
+// -*- C++ -*-
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef _LIBCPP_EXPERIMENTAL_STACKTRACE_ALLOC
+#define _LIBCPP_EXPERIMENTAL_STACKTRACE_ALLOC
+
+#include <__config>
+#include <__functional/function.h>
+#include <__memory/allocator_traits.h>
+#include <__memory_resource/memory_resource.h>
+#include <__memory_resource/polymorphic_allocator.h>
+#include <cstddef>
+#include <list>
+#include <memory>
+#include <string>
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+class stacktrace_entry;
+
+namespace __stacktrace {
+
+/** Per-stacktrace-invocation allocator which wraps a caller-provided allocator of any type.
+This is intended to be used with `std::pmr::` containers and strings throughout the stacktrace
+creation process. */
+struct alloc final : std::pmr::memory_resource {
+  template <class _Allocator>
+  _LIBCPP_HIDE_FROM_ABI explicit alloc(_Allocator const& __a) {
+    // Take the given allocator type, and rebind with a new type having <byte> as the template arg
+    using _AT       = std::allocator_traits<_Allocator>;
+    using _BA       = typename _AT::template rebind_alloc<std::byte>;
+    auto __ba       = _BA(__a);
+    __alloc_func_   = [__ba](size_t __sz) mutable { return __ba.allocate(__sz); };
+    __dealloc_func_ = [__ba](void* __ptr, size_t __sz) mutable { return __ba.deallocate((std::byte*)__ptr, __sz); };
+    __alloc_opaque_ = std::addressof(__a);
+  }
+
+  _LIBCPP_HIDE_FROM_ABI_VIRTUAL ~alloc() override = default;
+
+  _LIBCPP_HIDE_FROM_ABI_VIRTUAL virtual void _anchor_vfunc();
+
+  _LIBCPP_HIDE_FROM_ABI_VIRTUAL void* do_allocate(size_t __size, size_t __align) override {
+    // Avoiding "assert" in a system header, but we expect this to hold:
+    // assert(__align <= alignof(std::max_align_t));
+    (void)__align;
+    return __alloc_func_(__size);
+  }
+
+  _LIBCPP_HIDE_FROM_ABI_VIRTUAL void do_deallocate(void* __ptr, size_t __size, size_t __align) override {
+    (void)__align;
+    __dealloc_func_((std::byte*)__ptr, __size);
+  }
+
+  _LIBCPP_HIDE_FROM_ABI_VIRTUAL bool do_is_equal(std::pmr::memory_resource const& __rhs) const noexcept override {
+    auto* __rhs_ba = dynamic_cast<alloc const*>(&__rhs);
+    return __rhs_ba && (__rhs_ba->__alloc_opaque_ == __alloc_opaque_);
+  }
+
+  _LIBCPP_HIDE_FROM_ABI std::pmr::string new_string(size_t __size = 0) {
+    std::pmr::string __ret{this};
+    if (__size) {
+      __ret.reserve(__size);
+      __ret[0] = 0;
+    }
+    return __ret;
+  }
+
+  _LIBCPP_HIDE_FROM_ABI std::pmr::string hex_string(uintptr_t __addr) {
+    char __ret[19]; // "0x" + 16 digits + NUL
+    auto __size = snprintf(__ret, sizeof(__ret), "0x%016llx", (unsigned long long)__addr);
+    return {__ret, size_t(__size), this};
+  }
+
+  _LIBCPP_HIDE_FROM_ABI std::pmr::string u64_string(uintptr_t __val) {
+    char __ret[21]; // 20 digits max + NUL
+    auto __size = snprintf(__ret, sizeof(__ret), "%zu", __val);
+    return {__ret, size_t(__size), this};
+  }
+
+  template <typename _Tp>
+  _LIBCPP_HIDE_FROM_ABI std::pmr::list<_Tp> new_list() {
+    return std::pmr::list<_Tp>{this};
+  }
+
+  _LIBCPP_HIDE_FROM_ABI std::pmr::list<std::pmr::string> new_string_list() { return new_list<std::pmr::string>(); }
+
+private:
+  std::function<std::byte*(size_t)> __alloc_func_;
+  std::function<void(std::byte*, size_t)> __dealloc_func_;
+  /** Only used for equality */
+  void const* __alloc_opaque_;
+};
+
+} // namespace __stacktrace
+_LIBCPP_END_NAMESPACE_STD
+
+#endif // _LIBCPP_EXPERIMENTAL_STACKTRACE_ALLOC
diff --git a/libcxx/include/experimental/__stacktrace/detail/context.h b/libcxx/include/experimental/__stacktrace/detail/context.h
new file mode 100644
index 0000000000000..df791b37b386d
--- /dev/null
+++ b/libcxx/include/experimental/__stacktrace/detail/context.h
@@ -0,0 +1,53 @@
+// -*- C++ -*-
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef _LIBCPP_EXPERIMENTAL_STACKTRACE_CONTEXT
+#define _LIBCPP_EXPERIMENTAL_STACKTRACE_CONTEXT
+
+#include <__config>
+#include <__memory_resource/memory_resource.h>
+#include <__memory_resource/polymorphic_allocator.h>
+#include <__vector/pmr.h>
+#include <__vector/vector.h>
+#include <cstddef>
+#include <string>
+
+#include <experimental/__stacktrace/detail/alloc.h>
+#include <experimental/__stacktrace/detail/entry.h>
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+struct _LIBCPP_HIDE_FROM_ABI alloc;
+struct _LIBCPP_HIDE_FROM_ABI entry;
+
+namespace __stacktrace {
+
+/** Represents the state of the current in-progress stacktrace operation.  This includes
+the working list of `entry` objects, as well as the caller-provided allocator (wrapped
+in `polymorphic_allocator`) and a handful of utility functions involving that allocator. */
+struct _LIBCPP_HIDE_FROM_ABI context {
+  /** Encapsulates and type-removes the caller's allocator. */
+  alloc& __alloc_;
+
+  /** The working set of entry data; these will later be copied to their final `stacktrace_entry` objects. */
+  std::pmr::list<entry> __entries_;
+
+  /** Path to this process's main executable. */
+  std::pmr::string __main_prog_path_;
+
+  _LIBCPP_HIDE_FROM_ABI explicit context(alloc& __byte_alloc)
+      : __alloc_(__byte_alloc), __entries_(&__alloc_), __main_prog_path_(__alloc_.new_string()) {}
+
+  _LIBCPP_NO_TAIL_CALLS _LIBCPP_NOINLINE void do_stacktrace(size_t __skip, size_t __max_depth);
+};
+
+} // namespace __stacktrace
+_LIBCPP_END_NAMESPACE_STD
+
+#endif // _LIBCPP_EXPERIMENTAL_STACKTRACE_CONTEXT
diff --git a/libcxx/include/experimental/__stacktrace/detail/entry.h b/libcxx/include/experimental/__stacktrace/detail/entry.h
new file mode 100644
index 0000000000000..2bab14228b508
--- /dev/null
+++ b/libcxx/include/experimental/__stacktrace/detail/entry.h
@@ -0,0 +1,44 @@
+// -*- C++ -*-
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef _LIBCPP_EXPERIMENTAL_STACKTRACE_DETAIL_ENTRY
+#define _LIBCPP_EXPERIMENTAL_STACKTRACE_DETAIL_ENTRY
+
+#include <__config>
+#include <cstdint>
+#include <string>
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+namespace __stacktrace {
+
+/** Contains fields which will be used to generate the final `std::stacktrace_entry`.
+This is an intermediate object which owns strings allocated via the caller-provided allocator,
+which are later freed back to that allocator and converted to plain `std::string`s. */
+struct _LIBCPP_HIDE_FROM_ABI entry {
+  /** Caller's / faulting insn's address, including ASLR/slide */
+  uintptr_t __addr_{};
+
+  /** the address minus its image's slide offset */
+  uintptr_t __addr_unslid_{};
+
+  /** entry's description (symbol name) */
+  std::pmr::string __desc_{};
+
+  /** source file name */
+  std::pmr::string __file_{};
+
+  /** line number in source file */
+  uint32_t __line_{};
+};
+
+} // namespace __stacktrace
+_LIBCPP_END_NAMESPACE_STD
+
+#endif // _LIBCPP_EXPERIMENTAL_STACKTRACE_DETAIL_ENTRY
diff --git a/libcxx/include/experimental/__stacktrace/detail/to_string.h b/libcxx/include/experimental/__stacktrace/detail/to_string.h
new file mode 100644
index 0000000000000..47feddf07faf9
--- /dev/null
+++ b/libcxx/include/experimental/__stacktrace/detail/to_string.h
@@ -0,0 +1,46 @@
+// -*- C++ -*-
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef _LIBCPP_EXPERIMENTAL_STACKTRACE_TO_STRING
+#define _LIBCPP_EXPERIMENTAL_STACKTRACE_TO_STRING
+
+#include <__config>
+#include <__fwd/sstream.h>
+#include <__ostream/basic_ostream.h>
+#include <cstddef>
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+template <class _Allocator>
+class _LIBCPP_EXPORTED_FROM_ABI basic_stacktrace;
+
+class _LIBCPP_EXPORTED_FROM_ABI stacktrace_entry;
+
+namespace __stacktrace {
+
+struct _LIBCPP_HIDE_FROM_ABI __to_string {
+  _LIBCPP_HIDE_FROM_ABI string operator()(stacktrace_entry const& __entry);
+
+  _LIBCPP_HIDE_FROM_ABI void operator()(ostream& __os, stacktrace_entry const& __entry);
+
+  _LIBCPP_HIDE_FROM_ABI void operator()(ostream& __os, std::stacktrace_entry const* __entries, size_t __count);
+
+  string operator()(std::stacktrace_entry const* __entries, size_t __count);
+
+  template <class _Allocator>
+  _LIBCPP_HIDE_FROM_ABI string operator()(basic_stacktrace<_Allocator> const& __st) {
+    return (*this)(__st.__entries_.data(), __st.__entries_.size());
+  }
+};
+
+} // namespace __stacktrace
+
+_LIBCPP_END_NAMESPACE_STD
+
+#endif // _LIBCPP_EXPERIMENTAL_STACKTRACE_TO_STRING
diff --git a/libcxx/include/experimental/__stacktrace/stacktrace_entry.h b/libcxx/include/experimental/__stacktrace/stacktrace_entry.h
new file mode 100644
index 0000000000000..be8abb3ea91b2
--- /dev/null
+++ b/libcxx/include/experimental/__stacktrace/stacktrace_entry.h
@@ -0,0 +1,111 @@
+// -*- C++ -*-
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef _LIBCPP_EXPERIMENTAL_STACKTRACE_ENTRY
+#define _LIBCPP_EXPERIMENTAL_STACKTRACE_ENTRY
+
+#include <__cstddef/byte.h>
+#include <__cstddef/ptrdiff_t.h>
+#include <__cstddef/size_t.h>
+#include <__format/formatter.h>
+#include <__functional/function.h>
+#include <__functional/hash.h>
+#include <__fwd/format.h>
+#include <__fwd/ostream.h>
+#include <__fwd/sstream.h>
+#include <__fwd/vector.h>
+#include <__iterator/iterator.h>
+#include <__iterator/iterator_traits.h>
+#include <__iterator/reverse_access.h>
+#include <__iterator/reverse_iterator.h>
+#include <__memory/allocator.h>
+#include <__memory/allocator_traits.h>
+#include <__utility/move.h>
+#include <__vector/pmr.h>
+#include <__vector/swap.h>
+#include <__vector/vector.h>
+#include <cstdint>
+#include <string>
+
+#include "experimental/__stacktrace/detail/entry.h"
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+class _LIBCPP_EXPORTED_FROM_ABI stacktrace_entry {
+public:
+  // (19.6.3.1) Overview [stacktrace.entry.overview]
+  using native_handle_type = uintptr_t;
+
+  // (19.6.3.2) [stacktrace.entry.cons], constructors
+  _LIBCPP_EXPORTED_FROM_ABI ~stacktrace_entry() noexcept                                            = default;
+  _LIBCPP_EXPORTED_FROM_ABI constexpr stacktrace_entry() noexcept                                   = default;
+  _LIBCPP_EXPORTED_FROM_ABI constexpr stacktrace_entry(const stacktrace_entry&) noexcept            = default;
+  _LIBCPP_EXPORTED_FROM_ABI constexpr stacktrace_entry& operator=(const stacktrace_entry&) noexcept = default;
+
+  // (19.6.3.3) [stacktrace.entry.obs], observers
+  [[nodiscard]] _LIBCPP_EXPORTED_FROM_ABI constexpr native_handle_type native_handle() const noexcept {
+    return __addr_;
+  }
+  [[nodiscard]] _LIBCPP_EXPORTED_FROM_ABI constexpr explicit operator bool() const noexcept {
+    return native_handle() != 0;
+  }
+
+  // (19.6.3.4) [stacktrace.entry.query], query
+  [[nodiscard]] _LIBCPP_EXPORTED_FROM_ABI string description() const { return __desc_; }
+  [[nodiscard]] _LIBCPP_EXPORTED_FROM_ABI string source_file() const { return __file_; }
+  [[nodiscard]] _LIBCPP_EXPORTED_FROM_ABI uint_least32_t source_line() const { return __line_; }
+
+  // (19.6.3.5) [stacktrace.entry.cmp], comparison
+  [[nodiscard]] _LIBCPP_EXPORTED_FROM_ABI friend constexpr bool
+  operator==(const stacktrace_entry& __x, const stacktrace_entry& __y) noexcept {
+    return __x.native_handle() == __y.native_handle();
+  }
+
+  [[nodiscard]] _LIBCPP_EXPORTED_FROM_ABI friend constexpr strong_ordering
+  operator<=>(const stacktrace_entry& __x, const stacktrace_entry& __y) noexcept {
+    return __x.native_handle() <=> __y.native_handle();
+  }
+
+  _LIBCPP_HIDE_FROM_ABI explicit stacktrace_entry(__stacktrace::entry&& __e)
+      : __addr_(__e.__addr_), __desc_(std::move(__e.__desc_)), __file_(std::move(__e.__file_)), __line_(__e.__line_) {}
+
+private:
+  uintptr_t __addr_{};
+  std::string __desc_{};
+  std::string __file_{};
+  uint_least32_t __line_{};
+};
+
+// (19.6.4.6)
+// Non-member functions [stacktrace.basic.nonmem]
+
+_LIBCPP_EXPORTED_FROM_ABI string to_string(const stacktrace_entry& __entry);
+_LIBCPP_EXPORTED_FROM_ABI ostream& operator<<(ostream& __os, const stacktrace_entry& __entry);
+
+// (19.6.5)
+// Formatting support [stacktrace.format]
+
+// TODO(stacktrace23): needs `formatter`
+template <>
+struct _LIBCPP_EXPORTED_FROM_ABI formatter<stacktrace_entry>;
+
+// (19.6.6)
+// Hash support [stacktrace.basic.hash]
+
+template <>
+struct _LIBCPP_EXPORTED_FROM_ABI hash<stacktrace_entry> {
+  [[nodiscard]] size_t operator()(stacktrace_entry const& __entry) const noexcept {
+    auto __addr = __entry.native_handle();
+    return hash<uintptr_t>()(__addr);
+  }
+};
+
+_LIBCPP_END_NAMESPACE_STD
+
+#endif // _LIBCPP_EXPERIMENTAL_STACKTRACE_ENTRY
diff --git a/libcxx/include/experimental/stacktrace b/libcxx/include/experimental/stacktrace
new file mode 100644
index 0000000000000..9e1f7259ca3da
--- /dev/null
+++ b/libcxx/include/experimental/stacktrace
@@ -0,0 +1,191 @@
+// -*- C++ -*-
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef _LIBCPP_EXPERIMENTAL_STACKTRACE
+#define _LIBCPP_EXPERIMENTAL_STACKTRACE
+
+/*
+  Header <stacktrace> synopsis
+  (19.6.2)
+
+#include <compare>  // see [compare.syn]
+
+namespace std {
+  // [stacktrace.entry], class stacktrace_entry
+  class stacktrace_entry;
+
+  // [stacktrace.basic], class template basic_stacktrace
+  template<class Allocator>
+    class basic_stacktrace;
+
+  // basic_stacktrace typedef-names
+  using stacktrace = basic_stacktrace<allocator<stacktrace_entry>>;
+
+  // [stacktrace.basic.nonmem], non-member functions
+  template<class Allocator>
+    void swap(basic_stacktrace<Allocator>& a, basic_stacktrace<Allocator>& b)
+      noexcept(noexcept(a.swap(b)));
+
+  string to_string(const stacktrace_entry& f);
+
+  template<class Allocator>
+    string to_string(const basic_stacktrace<Allocator>& st);
+
+  ostream& operator<<(ostream& os, const stacktrace_entry& f);
+  template<class Allocator>
+    ostream& operator<<(ostream& os, const basic_stacktrace<Allocator>& st);
+
+  // [stacktrace.format], formatting support
+  template<> struct formatter<stacktrace_entry>;
+  template<class Allocator> struct formatter<basic_stacktrace<Allocator>>;
+
+  namespace pmr {
+    using stacktrace = basic_stacktrace<polymorphic_allocator<stacktrace_entry>>;
+  }
+
+  // [stacktrace.basic.hash], hash support
+  template<class T> struct hash;
+  template<> struct hash<stacktrace_entry>;
+  template<class Allocator> struct hash<basic_stacktrace<Allocator>>;
+}
+
+// [stacktrace.entry]
+
+namespace std {
+  class stacktrace_entry {
+  public:
+    using native_handle_type = implementation-defined;
+
+    // [stacktrace.entry.cons], constructors
+    constexpr stacktrace_entry() noexcept;
+    constexpr stacktrace_entry(const stacktrace_entry& other) noexcept;
+    constexpr stacktrace_entry& operator=(const stacktrace_entry& other) noexcept;
+
+    ~stacktrace_entry();
+
+    // [stacktrace.entry.obs], observers
+    constexpr native_handle_type native_handle() const noexcept;
+    constexpr explicit operator bool() const noexcept;
+
+    // [stacktrace.entry.query], query
+    string description() const;
+    string source_file() const;
+    uint_least32_t source_line() const;
+
+    // [stacktrace.entry.cmp], comparison
+    friend constexpr bool operator==(const stacktrace_entry& x,
+                                     const stacktrace_entry& y) noexcept;
+    friend constexpr strong_ordering operator<=>(const stacktrace_entry& x,
+                                                 const stacktrace_entry& y) noexcept;
+  };
+}
+
+// [stacktrace.basic]
+
+namespace std {
+  template<class Allocator>
+  class basic_stacktrace {
+  public:
+    using value_type = stacktrace_entry;
+    using const_reference = const value_type&;
+    using reference = value_type&;
+    using const_iterator = implementation-defined;  // see [stacktrace.basic.obs]
+    using iterator = const_iterator;
+    using reverse_iterator = reverse_iterator<iterator>;
+    using const_reverse_iterator = reverse_iterator<const_iterator>;
+    using difference_type = implementation-defined;
+    using size_type = implementation-defined;
+    using allocator_type = Allocator;
+
+    // [stacktrace.basic.cons], creation and assignment
+    static basic_stacktrace current(const allocator_type& alloc = allocator_type()) noexcept;
+    static basic_stacktrace current(size_type skip,
+                                    const allocator_type& alloc = allocator_type()) noexcept;
+    static basic_stacktrace current(size_type skip, size_type max_depth,
+                                    const allocator_type& alloc = allocator_type()) noexcept;
+
+    basic_stacktrace() noexcept(is_nothrow_default_constructible_v<allocator_type>);
+    explicit basic_stacktrace(const allocator_type& alloc) noexcept;
+
+    basic_stacktrace(const basic_stacktrace& other);
+    basic_stacktrace(basic_stacktrace&& other) noexcept;
+    basic_stacktrace(const basic_stacktrace& other, const allocator_type& alloc);
+    basic_stacktrace(basic_stacktrace&& other, const allocator_type& alloc);
+    basic_stacktrace& operator=(const basic_stacktrace& other);
+    basic_stacktrace& operator=(basic_stacktrace&& other)
+      noexcept(allocator_traits<Allocator>::propagate_on_container_move_assignment::value ||
+        allocator_traits<Allocator>::is_always_equal::value);
+
+    ~basic_stacktrace();
+
+    // [stacktrace.basic.obs], observers
+    allocator_type get_allocator() const noexcept;
+
+    const_iterator begin() const noexcept;
+    const_iterator end() const noexcept;
+    const_reverse_iterator rbegin() const noexcept;
+    const_reverse_iterator rend() const noexcept;
+
+    const_iterator cbegin() const noexcept;
+    const_iterator cend() const noexcept;
+    const_reverse_iterator crbegin() const noexcept;
+    const_reverse_iterator crend() const noexcept;
+
+    bool empty() const noexcept;
+    size_type size() const noexcept;
+    size_type max_size() const noexcept;
+
+    const_reference operator[](size_type) const;
+    const_reference at(size_type) const;
+
+    // [stacktrace.basic.cmp], comparisons
+    template<class Allocator2>
+    friend bool operator==(const basic_stacktrace& x,
+                           const basic_stacktrace<Allocator2>& y) noexcept;
+    template<class Allocator2>
+    friend strong_ordering operator<=>(const basic_stacktrace& x,
+                                       const basic_stacktrace<Allocator2>& y) noexcept;
+
+    // [stacktrace.basic.mod], modifiers
+    void swap(basic_stacktrace& other)
+      noexcept(allocator_traits<Allocator>::propagate_on_container_swap::value ||
+        allocator_traits<Allocator>::is_always_equal::value);
+
+  private:
+    vector<value_type, allocator_type> frames_;         // exposition only
+  };
+}
+
+*/
+
+#if __cplusplus < 201103L && defined(_LIBCPP_USE_FROZEN_CXX03_HEADERS)
+#  include <__cxx03/__config>
+#else
+#  include <__config>
+
+#  if _LIBCPP_STD_VER >= 23
+
+#    include <compare> // [stacktrace.syn]
+
+#    if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
+#      pragma GCC system_header
+#    endif
+
+_LIBCPP_PUSH_MACROS
+#    include <__undef_macros>
+
+#    include "experimental/__stacktrace/basic_stacktrace.h"
+#    include "experimental/__stacktrace/stacktrace_entry.h"
+
+_LIBCPP_POP_MACROS
+
+#  endif // _LIBCPP_STD_VER >= 23
+#endif   // __cplusplus < 201103L && defined(_LIBCPP_USE_FROZEN_CXX03_HEADERS)
+
+#endif // _LIBCPP_EXPERIMENTAL_STACKTRACE
diff --git a/libcxx/include/module.modulemap.in b/libcxx/include/module.modulemap.in
index af928a63f2315..8867681832bcf 100644
--- a/libcxx/include/module.modulemap.in
+++ b/libcxx/include/module.modulemap.in
@@ -2225,6 +2225,16 @@ module std [system] {
       header "experimental/simd"
       export *
     }
+    module stacktrace {
+      private header "experimental/__stacktrace/basic_stacktrace.h"
+      private header "experimental/__stacktrace/detail/alloc.h"
+      private header "experimental/__stacktrace/detail/context.h"
+      private header "experimental/__stacktrace/detail/entry.h"
+      private header "experimental/__stacktrace/detail/to_string.h"
+      private header "experimental/__stacktrace/stacktrace_entry.h"
+      header "experimental/stacktrace"
+      export *
+    }
   }
 
   // Implementation detail headers that are private to libc++. These modules
diff --git a/libcxx/modules/std/stacktrace.inc b/libcxx/modules/std/stacktrace.inc
index c1184087c0df4..e92f730cec62c 100644
--- a/libcxx/modules/std/stacktrace.inc
+++ b/libcxx/modules/std/stacktrace.inc
@@ -8,7 +8,9 @@
 //===----------------------------------------------------------------------===//
 
 export namespace std {
-#if 0
+// TODO(stacktrace23): update this when stacktrace is taken out of experimental
+#if 0 //_LIBCPP_STD_VER >= 23
+
   // [stacktrace.entry], class stacktrace_­entry
   using std::stacktrace_entry;
 
@@ -31,5 +33,6 @@ export namespace std {
 
   // [stacktrace.basic.hash], hash support
   using std::hash;
-#endif
+
+#endif // _LIBCPP_STD_VER >= 23
 } // namespace std
diff --git a/libcxx/src/CMakeLists.txt b/libcxx/src/CMakeLists.txt
index 4e9bf900af4c5..b24b98da2bf46 100644
--- a/libcxx/src/CMakeLists.txt
+++ b/libcxx/src/CMakeLists.txt
@@ -309,6 +309,24 @@ add_custom_target(cxx DEPENDS ${LIBCXX_BUILD_TARGETS})
 # Build the experimental static library
 set(LIBCXX_EXPERIMENTAL_SOURCES
   experimental/keep.cpp
+  experimental/stacktrace/alloc.cpp
+  experimental/stacktrace/common/debug.cpp
+  experimental/stacktrace/common/fd.cpp
+  experimental/stacktrace/context.cpp
+  experimental/stacktrace/linux/linux-dl.cpp
+  experimental/stacktrace/linux/linux-elf.cpp
+  experimental/stacktrace/linux/linux-sym.cpp
+  experimental/stacktrace/osx/osx.cpp
+  experimental/stacktrace/stacktrace.cpp
+  experimental/stacktrace/tools/addr2line.cpp
+  experimental/stacktrace/tools/atos.cpp
+  experimental/stacktrace/tools/llvm_symbolizer.cpp
+  experimental/stacktrace/tools/toolspawner.cpp
+  experimental/stacktrace/unwind/unwind.cpp
+  experimental/stacktrace/windows/dbghelp_dll.cpp
+  experimental/stacktrace/windows/dll.cpp
+  experimental/stacktrace/windows/psapi_dll.cpp
+  experimental/stacktrace/windows/win_impl.cpp
   )
 
 if (LIBCXX_PSTL_BACKEND STREQUAL "libdispatch")
@@ -334,6 +352,7 @@ endif()
 
 add_library(cxx_experimental STATIC ${LIBCXX_EXPERIMENTAL_SOURCES})
 target_link_libraries(cxx_experimental PUBLIC cxx-headers)
+
 if (LIBCXX_ENABLE_SHARED)
   target_link_libraries(cxx_experimental PRIVATE cxx_shared)
 else()
diff --git a/libcxx/src/experimental/stacktrace/alloc.cpp b/libcxx/src/experimental/stacktrace/alloc.cpp
new file mode 100644
index 0000000000000..956e01b312d3b
--- /dev/null
+++ b/libcxx/src/experimental/stacktrace/alloc.cpp
@@ -0,0 +1,20 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include <__config>
+#include <__config_site>
+
+#include <experimental/__stacktrace/detail/alloc.h>
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+namespace __stacktrace {
+
+void alloc::_anchor_vfunc() {}
+
+} // namespace __stacktrace
+_LIBCPP_END_NAMESPACE_STD
diff --git a/libcxx/src/experimental/stacktrace/common/config.h b/libcxx/src/experimental/stacktrace/common/config.h
new file mode 100644
index 0000000000000..0915b57463deb
--- /dev/null
+++ b/libcxx/src/experimental/stacktrace/common/config.h
@@ -0,0 +1,41 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef _LIBCPP_STACKTRACE_CONFIG_H
+#define _LIBCPP_STACKTRACE_CONFIG_H
+
+#include <__config>
+#include <__config_site>
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+namespace __stacktrace {
+
+#if __has_include(<unwind.h>)
+#  define _LIBCPP_STACKTRACE_COLLECT_UNWIND
+#endif
+
+#if defined(__APPLE__)
+#  define _LIBCPP_STACKTRACE_APPLE
+#endif
+
+#if defined(__linux__)
+#  define _LIBCPP_STACKTRACE_LINUX
+#endif
+
+#if __has_include(<spawn.h>) && _LIBCPP_STACKTRACE_ALLOW_TOOLS_AT_RUNTIME
+#  define _LIBCPP_STACKTRACE_CAN_SPAWN_TOOLS
+#endif
+
+#if __has_include(<windows.h>) && __has_include(<dbghelp.h>) && __has_include(<psapi.h>)
+#  define _LIBCPP_STACKTRACE_WINDOWS
+#endif
+
+} // namespace __stacktrace
+_LIBCPP_END_NAMESPACE_STD
+
+#endif // _LIBCPP_STACKTRACE_CONFIG_H
diff --git a/libcxx/src/experimental/stacktrace/common/debug.cpp b/libcxx/src/experimental/stacktrace/common/debug.cpp
new file mode 100644
index 0000000000000..4f113e10c0c23
--- /dev/null
+++ b/libcxx/src/experimental/stacktrace/common/debug.cpp
@@ -0,0 +1,19 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "debug.h"
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+namespace __stacktrace {
+
+debug::~debug() = default;
+
+debug::dummy_ostream::~dummy_ostream() = default;
+
+} // namespace __stacktrace
+_LIBCPP_END_NAMESPACE_STD
diff --git a/libcxx/src/experimental/stacktrace/common/debug.h b/libcxx/src/experimental/stacktrace/common/debug.h
new file mode 100644
index 0000000000000..0cee301d42d8b
--- /dev/null
+++ b/libcxx/src/experimental/stacktrace/common/debug.h
@@ -0,0 +1,55 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef _LIBCPP_STACKTRACE_DEBUG_H
+#define _LIBCPP_STACKTRACE_DEBUG_H
+
+#include <__config>
+#include <iostream>
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+namespace __stacktrace {
+
+/** Debug-message output stream.  If `LIBCXX_STACKTRACE_DEBUG` is defined in the environment
+or as a macro with exactly the string `1` then this is enabled (prints to `std::cerr`);
+otherwise its does nothing by returning a dummy stream. */
+struct debug : std::ostream {
+  virtual ~debug();
+
+  static bool enabled() {
+#if defined(LIBCXX_STACKTRACE_DEBUG) && LIBCXX_STACKTRACE_DEBUG == 1
+    return true;
+#else
+    static bool ret = [] {
+      auto const* val = getenv("LIBCXX_STACKTRACE_DEBUG");
+      return val && !strncmp(val, "1", 1);
+    }();
+    return ret;
+#endif
+  }
+
+  /** No-op output stream. */
+  struct dummy_ostream final : std::ostream {
+    virtual ~dummy_ostream();
+    friend std::ostream& operator<<(dummy_ostream& bogus, auto const&) { return bogus; }
+  };
+
+  friend std::ostream& operator<<(debug& dp, auto const& val) {
+    static dummy_ostream kdummy;
+    if (!enabled()) {
+      return kdummy;
+    }
+    std::cerr << val;
+    return std::cerr;
+  }
+};
+
+} // namespace __stacktrace
+_LIBCPP_END_NAMESPACE_STD
+
+#endif // _LIBCPP_STACKTRACE_DEBUG_H
diff --git a/libcxx/src/experimental/stacktrace/common/failed.h b/libcxx/src/experimental/stacktrace/common/failed.h
new file mode 100644
index 0000000000000..e53eb1123aabc
--- /dev/null
+++ b/libcxx/src/experimental/stacktrace/common/failed.h
@@ -0,0 +1,29 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef _LIBCPP_STACKTRACE_FAILED_H
+#define _LIBCPP_STACKTRACE_FAILED_H
+
+#include <stdexcept>
+
+// TODO(stacktrace23) Use std::expected instead?
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+namespace __stacktrace {
+
+struct failed : std::runtime_error {
+  virtual ~failed() = default;
+  int errno_{0};
+  failed() : std::runtime_error({}) {}
+  failed(char const* msg, int err) : std::runtime_error(msg), errno_(err) {}
+};
+
+} // namespace __stacktrace
+_LIBCPP_END_NAMESPACE_STD
+
+#endif // _LIBCPP_STACKTRACE_FAILED_H
diff --git a/libcxx/src/experimental/stacktrace/common/fd.cpp b/libcxx/src/experimental/stacktrace/common/fd.cpp
new file mode 100644
index 0000000000000..b7728ea7826dd
--- /dev/null
+++ b/libcxx/src/experimental/stacktrace/common/fd.cpp
@@ -0,0 +1,31 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "fd.h"
+#include "failed.h"
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+namespace __stacktrace {
+
+fd_streambuf::~fd_streambuf() = default;
+fd_istream::~fd_istream()     = default;
+
+int fd_streambuf::underflow() {
+  int bytesRead = ::read(fd_, buf_, size_);
+  if (bytesRead < 0) {
+    throw failed("I/O error reading from child process", errno);
+  }
+  if (bytesRead == 0) {
+    return traits_type::eof();
+  }
+  setg(buf_, buf_, buf_ + bytesRead);
+  return int(*buf_);
+}
+
+} // namespace __stacktrace
+_LIBCPP_END_NAMESPACE_STD
diff --git a/libcxx/src/experimental/stacktrace/common/fd.h b/libcxx/src/experimental/stacktrace/common/fd.h
new file mode 100644
index 0000000000000..ff003e16a6bd8
--- /dev/null
+++ b/libcxx/src/experimental/stacktrace/common/fd.h
@@ -0,0 +1,122 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef _LIBCPP_STACKTRACE_FD_H
+#define _LIBCPP_STACKTRACE_FD_H
+
+#include <__config>
+#include <cassert>
+#include <cerrno>
+#include <cstdio>
+#include <iostream>
+#include <sys/fcntl.h>
+#include <sys/mman.h>
+#include <unistd.h>
+#include <utility>
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+namespace __stacktrace {
+
+/** Encapsulates a plain old file descriptor `int`.  Avoids copies in order to
+force some component to "own" this, although it's freely convertible back to
+integer form.  Default-constructed, closed, and moved-out-of instances will have
+the invalid fd `-1`. */
+class fd {
+  int fd_{-1};
+
+public:
+  fd() : fd(-1) {}
+  fd(int fdint) : fd_(fdint) {}
+
+  fd(fd const&)            = delete;
+  fd& operator=(fd const&) = delete;
+
+  fd(fd&& rhs) {
+    if (&rhs != this) {
+      std::exchange(fd_, rhs.fd_);
+    }
+  }
+
+  fd& operator=(fd&& rhs) { return *new (this) fd(std::move(rhs)); }
+
+  ~fd() { close(); }
+
+  /** Returns true IFF fd is above zero */
+  bool valid() const { return fd_ > 0; }
+
+  /* implicit */ operator int() const {
+    auto ret = fd_;
+    assert(ret > 0);
+    return ret;
+  }
+
+  void close() {
+    int fd_old = -1;
+    std::exchange(fd_old, fd_);
+    if (fd_old != -1) {
+      ::close(fd_old);
+    }
+  }
+
+  static fd& null_fd() {
+    static fd ret = {::open("/dev/null", O_RDWR)};
+    return ret;
+  }
+
+  static fd open(std::string_view path) {
+    fd ret = {::open(path.data(), O_RDONLY)};
+    return ret;
+  }
+};
+
+/** Wraps a readable fd using the `streambuf` interface.  I/O errors arising
+from reading the provided fd will result in a `Failed` being thrown. */
+struct fd_streambuf final : std::streambuf {
+  fd& fd_;
+  char* buf_;
+  size_t size_;
+  fd_streambuf(fd& fd, char* buf, size_t size) : fd_(fd), buf_(buf), size_(size) {}
+  virtual ~fd_streambuf();
+  int underflow() override;
+};
+
+/** Wraps an `FDInStreamBuffer` in an `istream` */
+struct fd_istream final : std::istream {
+  fd_streambuf& buf_;
+  virtual ~fd_istream();
+  explicit fd_istream(fd_streambuf& buf) : std::istream(nullptr), buf_(buf) { rdbuf(&buf_); }
+};
+
+struct fd_mmap final {
+  fd fd_{};
+  size_t size_{0};
+  std::byte const* addr_{nullptr};
+
+  explicit fd_mmap(std::string_view path) : fd_mmap(fd::open(path)) {}
+
+  explicit fd_mmap(fd&& fd) : fd_(std::move(fd)) {
+    if (fd_) {
+      if ((size_ = ::lseek(fd, 0, SEEK_END))) {
+        addr_ = (std::byte const*)::mmap(nullptr, size_, PROT_READ, MAP_SHARED, fd_, 0);
+      }
+    }
+  }
+
+  operator bool() const { return addr_; }
+
+  ~fd_mmap() {
+    if (addr_) {
+      ::munmap(const_cast<void*>((void const*)addr_), size_);
+    }
+  }
+};
+
+} // namespace __stacktrace
+_LIBCPP_END_NAMESPACE_STD
+
+#endif // _LIBCPP_STACKTRACE_FD_H
diff --git a/libcxx/src/experimental/stacktrace/common/images.h b/libcxx/src/experimental/stacktrace/common/images.h
new file mode 100644
index 0000000000000..cb9eac47cf9dd
--- /dev/null
+++ b/libcxx/src/experimental/stacktrace/common/images.h
@@ -0,0 +1,33 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef _LIBCPP_STACKTRACE_IMAGES_H
+#define _LIBCPP_STACKTRACE_IMAGES_H
+
+#include <cstdint>
+#include <string_view>
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+namespace __stacktrace {
+
+constexpr unsigned k_max_images = 256;
+
+struct image {
+  uintptr_t loaded_at_{};
+  intptr_t slide_{};
+  std::string_view name_{};
+  bool is_main_prog_{};
+
+  bool operator<(image const& rhs) const { return loaded_at_ < rhs.loaded_at_; }
+  operator bool() const { return !name_.empty(); }
+};
+
+} // namespace __stacktrace
+_LIBCPP_END_NAMESPACE_STD
+
+#endif // _LIBCPP_STACKTRACE_IMAGES_H
diff --git a/libcxx/src/experimental/stacktrace/context.cpp b/libcxx/src/experimental/stacktrace/context.cpp
new file mode 100644
index 0000000000000..3d311af4d7a89
--- /dev/null
+++ b/libcxx/src/experimental/stacktrace/context.cpp
@@ -0,0 +1,104 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include <__config>
+#include <__config_site>
+
+#include <list>
+
+#include <experimental/__stacktrace/basic_stacktrace.h>
+#include <experimental/__stacktrace/stacktrace_entry.h>
+
+#include <experimental/__stacktrace/detail/alloc.h>
+#include <experimental/__stacktrace/detail/context.h>
+#include <experimental/__stacktrace/detail/entry.h>
+#include <experimental/__stacktrace/detail/to_string.h>
+
+#include "common/config.h"
+
+#if defined(_LIBCPP_STACKTRACE_LINUX)
+#  include "linux/linux.h"
+#endif
+
+#if defined(_LIBCPP_STACKTRACE_APPLE)
+#  include "osx/osx.h"
+#endif
+
+#if defined(_LIBCPP_STACKTRACE_CAN_SPAWN_TOOLS)
+#  include "tools/pspawn.h"
+#endif
+
+#if defined(_LIBCPP_STACKTRACE_COLLECT_UNWIND)
+#  include "unwind/unwind.h"
+#endif
+
+#if defined(_LIBCPP_STACKTRACE_USE_DBGHELP)
+#  include "windows/win_impl.h"
+#endif
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+namespace __stacktrace {
+
+_LIBCPP_NO_TAIL_CALLS _LIBCPP_NOINLINE void context::do_stacktrace(size_t skip, size_t max_depth) {
+  /*
+  Here we declare stacktrace components or "backends" which will handle the different tasks:
+
+  (1) get the addresses from the call stack
+  (2) identify program images in process virtual space (program binary, plus modules, shared/dynamic libs)
+  (3) resolve using debug info, and possibly with an external tool on the $PATH
+  (4+) extra passes to get symbols, in case 3 couldn't
+
+  Based on the macros produced by `stacktrace.h`, throw all backends we have available at the task.  Ideally the #ifdef
+  gauntlet below should result in one of each of the above functions: (1) collector, (2) mod_ident, (3) resolver, (4)
+  symbolizer.  If any are missing or duplicated that is still fine; we work with zero or all the available utilities.
+
+  All these classes do their best to provide any of the requested fields they can: (symbol, filename, source line),
+  substituting if needed with something reasonable.  For example, if the source filename and line are not available
+  then we will at least report that the address and symbol are in the module `foo.exe`.
+
+  These components should also tolerate: missing data, weirdly-formatted data (e.g. from the external tools), or even
+  already-populated data.  We take care not to crash / abort / throw in any of these, and we'll silently fail.  See
+  `common/debug.h` for a debugging logger you can enable at runtime.
+  */
+
+#if defined(_LIBCPP_STACKTRACE_USE_DBGHELP)
+  win_impl dbghelp{*this};
+  auto& collector  = dbghelp;
+  auto& mod_ident  = dbghelp;
+  auto& resolver   = dbghelp;
+  auto& symbolizer = dbghelp;
+#endif
+#if defined(_LIBCPP_STACKTRACE_COLLECT_UNWIND)
+  unwind unwind{*this};
+  auto& collector = unwind;
+#endif
+#if defined(_LIBCPP_STACKTRACE_APPLE)
+  osx osx{*this};
+  auto& mod_ident  = osx;
+  auto& symbolizer = osx;
+#endif
+#if defined(_LIBCPP_STACKTRACE_LINUX)
+  linux linux{*this};
+  auto& mod_ident  = linux;
+  auto& symbolizer = linux;
+#endif
+#if defined(_LIBCPP_STACKTRACE_CAN_SPAWN_TOOLS)
+  spawner pspawn{*this};
+  auto& resolver = pspawn;
+#endif
+
+  collector.collect(skip + 1, max_depth); // First get the instruction addresses, populate __entries_
+  if (__entries_.size()) {                // (Can't proceed if empty)
+    mod_ident.ident_modules();            // Associate addrs with binaries (ELF/MachO/etc.)
+    resolver.resolve_lines();             // Resolve addresses to symbols, filename, linenumber
+    symbolizer.symbolize();               // Populate missing symbols, if any.
+  }
+}
+
+} // namespace __stacktrace
+_LIBCPP_END_NAMESPACE_STD
diff --git a/libcxx/src/experimental/stacktrace/linux/elf.h b/libcxx/src/experimental/stacktrace/linux/elf.h
new file mode 100644
index 0000000000000..214e8cc5a7819
--- /dev/null
+++ b/libcxx/src/experimental/stacktrace/linux/elf.h
@@ -0,0 +1,315 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef _LIBCPP_STACKTRACE_ELF_H
+#define _LIBCPP_STACKTRACE_ELF_H
+
+#include <cstddef>
+#include <cstdint>
+#include <cstdio>
+#include <cstdlib>
+#include <functional>
+#include <string_view>
+#include <sys/fcntl.h>
+#include <unistd.h>
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+namespace __stacktrace {
+
+// Includes ELF constants and structs copied from <elf.h>, with a few changes.
+
+namespace elf {
+
+struct Header32 final {
+  uint8_t ident[16];  /* Magic number and other info */
+  uint16_t type;      /* Object file type */
+  uint16_t machine;   /* Architecture */
+  uint32_t version;   /* Object file version */
+  uint32_t entry;     /* Entry point virtual address */
+  uint32_t phoff;     /* Program header table file offset */
+  uint32_t shoff;     /* Section header table file offset */
+  uint32_t flags;     /* Processor-specific flags */
+  uint16_t ehsize;    /* ELF header size in bytes */
+  uint16_t phentsize; /* Program header table entry size */
+  uint16_t phnum;     /* Program header table entry count */
+  uint16_t shentsize; /* Section header table entry size */
+  uint16_t shnum;     /* Section header table entry count */
+  uint16_t shstrndx;  /* Section header string table index */
+};
+
+struct Section32 final {
+  uint32_t name;      /* Section name (string tbl index) */
+  uint32_t type;      /* Section type */
+  uint32_t flags;     /* Section flags */
+  uint32_t addr;      /* Section virtual addr at execution */
+  uint32_t offset;    /* Section file offset */
+  uint32_t size;      /* Section size in bytes */
+  uint32_t link;      /* Link to another section */
+  uint32_t info;      /* Additional section information */
+  uint32_t addralign; /* Section alignment */
+  uint32_t entsize;   /* Entry size if section holds table */
+};
+
+struct Symbol32 final {
+  uint32_t name;  /* Symbol name (string tbl index) */
+  uint32_t value; /* Symbol value */
+  uint32_t size;  /* Symbol size */
+  uint8_t info;   /* Symbol type and binding */
+  uint8_t other;  /* Symbol visibility */
+  uint16_t shndx; /* Section index */
+};
+
+struct Header64 final {
+  uint8_t ident[16];  /* Magic number and other info */
+  uint16_t type;      /* Object file type */
+  uint16_t machine;   /* Architecture */
+  uint32_t version;   /* Object file version */
+  uint64_t entry;     /* Entry point virtual address */
+  uint64_t phoff;     /* Program header table file offset */
+  uint64_t shoff;     /* Section header table file offset */
+  uint32_t flags;     /* Processor-specific flags */
+  uint16_t ehsize;    /* ELF header size in bytes */
+  uint16_t phentsize; /* Program header table entry size */
+  uint16_t phnum;     /* Program header table entry count */
+  uint16_t shentsize; /* Section header table entry size */
+  uint16_t shnum;     /* Section header table entry count */
+  uint16_t shstrndx;  /* Section header string table index */
+};
+
+struct Section64 final {
+  uint32_t name;      /* Section name (string tbl index) */
+  uint32_t type;      /* Section type */
+  uint64_t flags;     /* Section flags */
+  uint64_t addr;      /* Section virtual addr at execution */
+  uint64_t offset;    /* Section file offset */
+  uint64_t size;      /* Section size in bytes */
+  uint32_t link;      /* Link to another section */
+  uint32_t info;      /* Additional section information */
+  uint64_t addralign; /* Section alignment */
+  uint64_t entsize;   /* Entry size if section holds table */
+};
+
+struct Symbol64 final {
+  uint32_t name;  /* Symbol name (string tbl index) */
+  uint8_t info;   /* Symbol type and binding */
+  uint8_t other;  /* Symbol visibility */
+  uint16_t shndx; /* Section index */
+  uint64_t value; /* Symbol value */
+  uint64_t size;  /* Symbol size */
+};
+
+/** Represents an ELF header.  Supports the minimum needed to navigate an ELF file's sections and get at the symbol and
+ * string tables. */
+struct Header final {
+  std::byte const* ptr_{};
+  uintptr_t shoff_{};
+  size_t shnum_{};
+  size_t shstrndx_{};
+
+  Header()              = default;
+  Header(Header const&) = default;
+  Header& operator=(Header const& rhs) { return *new (this) Header(rhs); }
+
+  operator bool() { return ptr_; }
+
+  template <class H>
+  explicit Header(H* h)
+      : ptr_((std::byte const*)h),
+        shoff_(uintptr_t(h->shoff)),
+        shnum_(size_t(h->shnum)),
+        shstrndx_(size_t(h->shstrndx)) {}
+};
+
+struct ELF;
+struct StringTable;
+
+struct Section final {
+  constexpr static uint32_t kSymTab = 2; // symbol table
+  constexpr static uint32_t kStrTab = 3; // name table for symbols or sections
+
+  ELF* elf_{};
+  std::byte const* ptr_{};
+  uintptr_t nameIndex_{};
+  uint32_t type_{};
+  uintptr_t offset_{};
+  size_t size_{};
+
+  Section() = default;
+
+  template <class S>
+  Section(ELF* elf, S* sec)
+      : elf_(elf),
+        ptr_((std::byte const*)sec),
+        nameIndex_(sec->name),
+        type_(sec->type),
+        offset_(sec->offset),
+        size_(sec->size) {}
+
+  operator bool() const { return ptr_; }
+
+  template <class T = std::byte>
+  T const* data() const {
+    return (T const*)(elfBase() + offset_);
+  }
+
+  std::byte const* elfBase() const;
+  std::string_view name() const;
+};
+
+struct Symbol final {
+  constexpr static uint8_t kFunc = 0x02; // STT_FUNC (code object)
+
+  ELF* elf_{};
+  std::byte const* ptr_{};
+  uintptr_t nameIndex_{};
+  uint32_t type_{};
+  uintptr_t value_{};
+
+  Symbol()              = default;
+  Symbol(Symbol const&) = default;
+  Symbol& operator=(Symbol const& rhs) { return *new (this) Symbol(rhs); }
+
+  operator bool() { return ptr_; }
+
+  bool isCode() const { return type_ == kFunc; }
+
+  template <class S>
+  Symbol(ELF* elf, S* sym)
+      : elf_(elf), ptr_((std::byte const*)sym), nameIndex_(sym->name), type_(0x0f & sym->info), value_(sym->value) {}
+
+  std::byte const* elfBase() const;
+  std::string_view name() const;
+};
+
+/** Represents one of the ELF's `strtab`s.  This is a block of string data, with strings appended one after another, and
+ * NUL-terminated.  Strings are indexed according to their starting offset.  At offset 0 is typically an empty string.
+ */
+struct StringTable {
+  std::string_view data_{};
+
+  StringTable() = default;
+
+  /* implicit */ StringTable(Section const& sec) : data_(sec.data<char>(), sec.size_) {}
+
+  operator bool() { return data_.size(); }
+
+  std::string_view at(size_t index) {
+    auto* ret = data_.data() + index;
+    return {ret, strlen(ret)};
+  }
+};
+
+/** Encapsulates an ELF image specified by byte-address (e.g. from an mmapped file or a program image or shared object
+ * in memory).  If given a supported ELF image, this will test true with `operator bool` to indicate it is supported and
+ * was able to parse some basic information from the header. */
+struct ELF {
+  Header header_{};
+  Section (*makeSection_)(ELF*, std::byte const*){};
+  Symbol (*makeSymbol_)(ELF*, std::byte const*){};
+  size_t secSize_{};
+  size_t symSize_{};
+  StringTable nametab_{};
+  Section symtab_{};
+  StringTable strtab_{};
+  size_t symCount_{};
+
+  static Section makeSection32(ELF* elf, std::byte const* ptr) { return Section(elf, (Section32 const*)ptr); }
+  static Section makeSection64(ELF* elf, std::byte const* ptr) { return Section(elf, (Section64 const*)ptr); }
+  static Symbol makeSymbol32(ELF* elf, std::byte const* ptr) { return Symbol(elf, (Symbol32 const*)ptr); }
+  static Symbol makeSymbol64(ELF* elf, std::byte const* ptr) { return Symbol(elf, (Symbol64 const*)ptr); }
+
+  operator bool() { return header_; }
+
+  explicit ELF(std::byte const* image) {
+    auto* p = (uint8_t const*)image;
+    // Bytes 0..3: magic bytes: 0x7F, 'E', 'L', 'F'
+    if (*p++ == 0x7f && *p++ == 0x45 && *p++ == 0x4c && *p++ == 0x46) {
+      auto klass       = *p++; // Byte 4 (EI_CLASS): ELF class, 32- or 64-bit (0x01 or 0x02)
+      auto dataFormat  = *p++; // Byte 5 (EI_DATA): (0x01) little- or (0x02) big-endian
+      auto fileVersion = *p++; // Byte 6 (EI_VERSION): ELF version: expect 1 (latest ELF version)
+      constexpr static uint16_t kEndianTestWord{0x0201};
+      auto hostEndianness = *(uint8_t const*)&kEndianTestWord;
+      if (dataFormat == hostEndianness && fileVersion == 1) {
+        if (klass == 0x01) {
+          header_      = Header((Header32 const*)image);
+          makeSection_ = makeSection32;
+          makeSymbol_  = makeSymbol32;
+          secSize_     = sizeof(Section32);
+          symSize_     = sizeof(Symbol32);
+        } else if (klass == 0x02) {
+          header_      = Header((Header64 const*)image);
+          makeSection_ = makeSection64;
+          makeSymbol_  = makeSymbol64;
+          secSize_     = sizeof(Section64);
+          symSize_     = sizeof(Symbol64);
+        }
+      }
+    }
+    if (*this) {
+      nametab_ = section(header_.shstrndx_);
+      eachSection([&](auto& sec) mutable -> bool {
+        if (sec.type_ == Section::kSymTab && sec.name() == ".symtab") {
+          symtab_ = sec;
+        } else if (sec.type_ == Section::kStrTab && sec.name() == ".strtab") {
+          strtab_ = sec;
+        }
+        return !symtab_ || !strtab_;
+      });
+    }
+    if (symtab_) {
+      symCount_ = symtab_.size_ / symSize_;
+    }
+  }
+
+  Section section(size_t index) {
+    auto* addr = header_.ptr_ + header_.shoff_ + (index * secSize_);
+    return makeSection_(this, addr);
+  }
+
+  Symbol symbol(size_t index) {
+    auto* addr = symtab_.data() + (index * symSize_);
+    return makeSymbol_(this, addr);
+  }
+
+  template <class T>
+  using CB = std::function<bool(T const&)>;
+
+  void eachSection(CB<Section> cb) {
+    for (size_t i = 0; i < header_.shnum_ && cb(section(i)); i++)
+      ;
+  }
+
+  void eachSymbol(CB<Symbol> cb) {
+    for (size_t i = 0; i < symCount_ && cb(symbol(i)); i++)
+      ;
+  }
+
+  Symbol getSym(uintptr_t addr) {
+    Symbol ret{};
+    eachSymbol([&](auto& sym) -> bool {
+      if (sym.value_ <= addr && sym.value_ > ret.value_) {
+        ret = sym;
+      }
+      return true;
+    });
+    return ret;
+  }
+};
+
+inline std::byte const* Section::elfBase() const { return elf_->header_.ptr_; }
+inline std::byte const* Symbol::elfBase() const { return elf_->header_.ptr_; }
+
+inline std::string_view Section::name() const { return elf_->nametab_.at(nameIndex_); }
+inline std::string_view Symbol::name() const { return elf_->strtab_.at(nameIndex_); }
+
+} // namespace elf
+
+} // namespace __stacktrace
+_LIBCPP_END_NAMESPACE_STD
+
+#endif
diff --git a/libcxx/src/experimental/stacktrace/linux/linux-dl.cpp b/libcxx/src/experimental/stacktrace/linux/linux-dl.cpp
new file mode 100644
index 0000000000000..62cad72b9f124
--- /dev/null
+++ b/libcxx/src/experimental/stacktrace/linux/linux-dl.cpp
@@ -0,0 +1,58 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "../common/config.h"
+
+#if defined(_LIBCPP_STACKTRACE_LINUX)
+
+#  include "linux.h"
+
+#  include <cassert>
+#  include <dlfcn.h>
+#  include <link.h>
+#  include <unistd.h>
+
+#  include "../common/images.h"
+
+#  include <experimental/__stacktrace/detail/context.h>
+#  include <experimental/__stacktrace/detail/entry.h>
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+namespace __stacktrace {
+
+void linux::ident_modules() {
+  auto& images = images::get();
+
+  // Aside from the left/right sentinels in the array (hence the 2),
+  // are there any other real images?
+  if (images.count_ <= 2) {
+    return;
+  }
+
+  auto mainProg = images.mainProg();
+  if (mainProg) {
+    cx_.__main_prog_path_ = mainProg->name_;
+  }
+
+  unsigned index = 1; // Starts at one, and is moved around in this loop
+  for (auto& entry : cx_.__entries_) {
+    while (images[index].loaded_at_ > entry.__addr_) {
+      --index;
+    }
+    while (images[index + 1].loaded_at_ <= entry.__addr_) {
+      ++index;
+    }
+    entry.__addr_unslid_ = entry.__addr_ - images[index].slide_;
+    entry.__file_        = images[index].name_;
+  }
+}
+
+} // namespace __stacktrace
+_LIBCPP_END_NAMESPACE_STD
+
+#endif // _LIBCPP_STACKTRACE_LINUX
diff --git a/libcxx/src/experimental/stacktrace/linux/linux-elf.cpp b/libcxx/src/experimental/stacktrace/linux/linux-elf.cpp
new file mode 100644
index 0000000000000..7cf82789ea2ed
--- /dev/null
+++ b/libcxx/src/experimental/stacktrace/linux/linux-elf.cpp
@@ -0,0 +1,53 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "../common/config.h"
+
+#if defined(_LIBCPP_STACKTRACE_LINUX)
+
+#  include "linux.h"
+
+#  include <cassert>
+#  include <unistd.h>
+
+#  include <experimental/__stacktrace/detail/context.h>
+#  include <experimental/__stacktrace/detail/entry.h>
+
+#  include "../common/fd.h"
+#  include "elf.h"
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+namespace __stacktrace {
+
+/**
+When trying to collect a stacktrace under Linux, there are narrow (but still quite common) cases where we will fail
+to resolve symbols.  Linux's `dl` doesn't want to read symbols from the non-exported symbol table at runtime,
+and older versions of `addr2line` or `llvm-symbolizer` will also not resolve these.
+
+This implementation the minimum necessary to resolve symbols.  It can identify this as an ELF (32 or 64 bits), locate
+the symbol and symbol-string table, and fill in any remaining missing symbols.
+*/
+void linux::resolve_main_elf_syms(std::string_view main_elf_name) {
+  // We can statically initialize these, because main_elf_name should be the same every time.
+  static fd_mmap _mm(main_elf_name);
+  if (_mm) {
+    static elf::ELF _this_elf(_mm.addr_);
+    if (_this_elf) {
+      for (auto& entry : cx_.__entries_) {
+        if (entry.__desc_.empty() && entry.__file_ == main_elf_name) {
+          entry.__desc_ = _this_elf.getSym(entry.__addr_unslid_).name();
+        }
+      }
+    }
+  }
+}
+
+} // namespace __stacktrace
+_LIBCPP_END_NAMESPACE_STD
+
+#endif // _LIBCPP_STACKTRACE_LINUX
diff --git a/libcxx/src/experimental/stacktrace/linux/linux-sym.cpp b/libcxx/src/experimental/stacktrace/linux/linux-sym.cpp
new file mode 100644
index 0000000000000..fa7489c64c923
--- /dev/null
+++ b/libcxx/src/experimental/stacktrace/linux/linux-sym.cpp
@@ -0,0 +1,61 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "../common/config.h"
+
+#if defined(_LIBCPP_STACKTRACE_LINUX)
+
+#  include "linux.h"
+
+#  include <cassert>
+#  include <dlfcn.h>
+#  include <unistd.h>
+
+#  include <experimental/__stacktrace/detail/context.h>
+#  include <experimental/__stacktrace/detail/entry.h>
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+namespace __stacktrace {
+
+bool symbolize_entry(entry& entry) {
+  bool ret = false;
+  Dl_info info;
+  if (dladdr((void*)entry.__addr_, &info)) {
+    ret = true; // at least partially successful
+    if (info.dli_fname && entry.__file_.empty()) {
+      // provide at least the binary filename in case we cannot lookup source location
+      entry.__file_ = info.dli_fname;
+    }
+    if (info.dli_sname && entry.__desc_.empty()) {
+      // provide at least the mangled name; try to unmangle in a later step
+      entry.__desc_ = info.dli_sname;
+    }
+  }
+  return ret;
+}
+
+// NOTE:  We can use `dlfcn` to resolve addresses to symbols, which works great --
+// except for symbols in the main program.  If addr2line-style tools are enabled, that step
+// might also be able to get symbols directly from the binary's debug info.
+void linux::symbolize() {
+  for (auto& entry : cx_.__entries_) {
+    symbolize_entry(entry);
+  }
+  // Symbols might be missing, because both (1) Linux's `dladdr` won't try to resolve non-exported symbols,
+  // which can be the case for the main program executable; and (2) debug info was not preserved.
+  // As a last resort, this function (see `linux-elf.cpp`) can still access symbol table directly.
+  image* mainELF = images::get().mainProg();
+  if (mainELF && !mainELF->name_.empty()) {
+    resolve_main_elf_syms(mainELF->name_);
+  }
+}
+
+} // namespace __stacktrace
+_LIBCPP_END_NAMESPACE_STD
+
+#endif // _LIBCPP_STACKTRACE_LINUX
diff --git a/libcxx/src/experimental/stacktrace/linux/linux.h b/libcxx/src/experimental/stacktrace/linux/linux.h
new file mode 100644
index 0000000000000..a8e8c2279f6fc
--- /dev/null
+++ b/libcxx/src/experimental/stacktrace/linux/linux.h
@@ -0,0 +1,98 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef _LIBCPP_STACKTRACE_LINUX_H
+#define _LIBCPP_STACKTRACE_LINUX_H
+
+#include "../common/config.h"
+
+#if defined(_LIBCPP_STACKTRACE_LINUX)
+
+#  include <algorithm>
+#  include <array>
+#  include <cassert>
+#  include <cstddef>
+#  include <cstdlib>
+#  include <link.h>
+#  include <string_view>
+#  include <unistd.h>
+
+#  include "../common/images.h"
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+namespace __stacktrace {
+
+struct _LIBCPP_HIDE_FROM_ABI context;
+
+struct linux {
+  context& cx_;
+  void ident_modules();
+  void symbolize();
+
+private:
+  void resolve_main_elf_syms(std::string_view elf_name);
+};
+
+struct images {
+  // How many images this contains, including the left/right sentinels.
+  unsigned count_{0};
+  std::array<image, k_max_images + 2> images_{};
+
+  int add(dl_phdr_info& info) {
+    assert(count_ < k_max_images);
+    auto isFirst        = (count_ == 0);
+    auto& image         = images_.at(count_++);
+    image.loaded_at_    = info.dlpi_addr;
+    image.slide_        = info.dlpi_addr;
+    image.name_         = info.dlpi_name;
+    image.is_main_prog_ = isFirst; // first one is the main ELF
+    if (image.name_.empty() && isFirst) {
+      static char buffer[PATH_MAX + 1];
+      uint32_t length = sizeof(buffer);
+      if (readlink("/proc/self/exe", buffer, length) > 0) {
+        image.name_ = buffer;
+      }
+    }
+    return count_ == k_max_images; // return nonzero if we're at the limit
+  }
+
+  static int callback(dl_phdr_info* info, size_t, void* self) { return (*(images*)(self)).add(*info); }
+
+  images() {
+    dl_iterate_phdr(images::callback, this);
+    images_[count_++] = {0uz, 0};  // sentinel at low end
+    images_[count_++] = {~0uz, 0}; // sentinel at high end
+    std::sort(images_.begin(), images_.begin() + count_ - 1);
+  }
+
+  image& operator[](size_t index) {
+    assert(index < count_);
+    return images_.at(index);
+  }
+
+  image* mainProg() {
+    for (auto& image : images_) {
+      if (image.is_main_prog_) {
+        return ℑ
+      }
+    }
+    return nullptr;
+  }
+
+  static images& get() {
+    static images images;
+    return images;
+  }
+};
+
+} // namespace __stacktrace
+_LIBCPP_END_NAMESPACE_STD
+
+#endif // _LIBCPP_STACKTRACE_LINUX
+
+#endif // _LIBCPP_STACKTRACE_LINUX_H
diff --git a/libcxx/src/experimental/stacktrace/osx/osx.cpp b/libcxx/src/experimental/stacktrace/osx/osx.cpp
new file mode 100644
index 0000000000000..c00a7ea94e780
--- /dev/null
+++ b/libcxx/src/experimental/stacktrace/osx/osx.cpp
@@ -0,0 +1,111 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "../common/config.h"
+
+#if defined(_LIBCPP_STACKTRACE_APPLE)
+
+#  include <algorithm>
+#  include <array>
+#  include <dlfcn.h>
+#  include <mach-o/dyld.h>
+#  include <mach-o/loader.h>
+
+#  include <experimental/__stacktrace/detail/context.h>
+#  include <experimental/__stacktrace/detail/entry.h>
+
+#  include "osx.h"
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+namespace __stacktrace {
+
+constexpr unsigned kMaxImages = 256;
+
+struct Image {
+  uintptr_t loadedAt{};
+  intptr_t slide{};
+  std::string_view name{};
+  bool operator<(Image const& rhs) const { return loadedAt < rhs.loadedAt; }
+  operator bool() const { return !name.empty(); }
+};
+
+void ident_module(entry& entry, unsigned& index, Image* images) {
+  if (entry.__addr_) {
+    while (images[index].loadedAt > entry.__addr_) {
+      --index;
+    }
+    while (images[index + 1].loadedAt <= entry.__addr_) {
+      ++index;
+    }
+    auto& image = images[index];
+    if (image) {
+      entry.__addr_unslid_ = entry.__addr_ - images[index].slide;
+      entry.__file_        = images[index].name;
+    }
+  }
+}
+
+bool enum_modules(unsigned& count, auto& images) {
+  count = std::min(kMaxImages, _dyld_image_count());
+  for (size_t i = 0; i < count; i++) {
+    auto& image    = images[i];
+    image.slide    = _dyld_get_image_vmaddr_slide(i);
+    image.loadedAt = uintptr_t(_dyld_get_image_header(i));
+    image.name     = _dyld_get_image_name(i);
+  }
+  images[count++] = {0uz, 0};  // sentinel at low end
+  images[count++] = {~0uz, 0}; // sentinel at high end
+  std::sort(images.begin(), images.begin() + count - 1);
+  return true;
+}
+
+void osx::ident_modules() {
+  static unsigned imageCount;
+  static std::array<Image, kMaxImages + 2> images;
+  static bool atomicInitialized = enum_modules(imageCount, images);
+  (void)atomicInitialized;
+
+  // Aside from the left/right sentinels in the array (hence the 2),
+  // are there any other real images?
+  if (imageCount <= 2) {
+    return;
+  }
+
+  // First image (the main program) is at index 1
+  cx_.__main_prog_path_ = images.at(1).name;
+
+  unsigned index = 1; // Starts at one, and is moved by 'ident_module'
+  for (auto& entry : cx_.__entries_) {
+    ident_module(entry, index, images.data());
+  }
+}
+
+void symbolize_entry(entry& entry) {
+  Dl_info info;
+  if (dladdr((void*)entry.__addr_, &info)) {
+    if (info.dli_fname && entry.__file_.empty()) {
+      // provide at least the binary filename in case we cannot lookup source location
+      entry.__file_ = info.dli_fname;
+    }
+    if (info.dli_sname && entry.__desc_.empty()) {
+      // provide at least the mangled name; try to unmangle in a later step
+      entry.__desc_ = info.dli_sname;
+    }
+  }
+}
+
+void osx::symbolize() {
+  for (auto& entry : cx_.__entries_) {
+    symbolize_entry(entry);
+  }
+}
+
+} // namespace __stacktrace
+_LIBCPP_END_NAMESPACE_STD
+
+#endif // _LIBCPP_STACKTRACE_APPLE
diff --git a/libcxx/src/experimental/stacktrace/osx/osx.h b/libcxx/src/experimental/stacktrace/osx/osx.h
new file mode 100644
index 0000000000000..ca0890929453e
--- /dev/null
+++ b/libcxx/src/experimental/stacktrace/osx/osx.h
@@ -0,0 +1,31 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef _LIBCPP_STACKTRACE_OSX_H
+#define _LIBCPP_STACKTRACE_OSX_H
+
+#include <__config>
+#include <__config_site>
+#include <cstddef>
+#include <cstdlib>
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+namespace __stacktrace {
+
+struct _LIBCPP_HIDE_FROM_ABI context;
+
+struct osx {
+  context& cx_;
+  void ident_modules();
+  void symbolize();
+};
+
+} // namespace __stacktrace
+_LIBCPP_END_NAMESPACE_STD
+
+#endif // _LIBCPP_STACKTRACE_OSX_H
diff --git a/libcxx/src/experimental/stacktrace/stacktrace.cpp b/libcxx/src/experimental/stacktrace/stacktrace.cpp
new file mode 100644
index 0000000000000..e33b94205a8ea
--- /dev/null
+++ b/libcxx/src/experimental/stacktrace/stacktrace.cpp
@@ -0,0 +1,94 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include <__config>
+#include <__config_site>
+
+#include <iomanip>
+#include <iostream>
+#include <sstream>
+#include <string>
+
+#include <experimental/__stacktrace/basic_stacktrace.h>
+#include <experimental/__stacktrace/stacktrace_entry.h>
+
+#include <experimental/__stacktrace/detail/alloc.h>
+#include <experimental/__stacktrace/detail/context.h>
+#include <experimental/__stacktrace/detail/entry.h>
+#include <experimental/__stacktrace/detail/to_string.h>
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+namespace __stacktrace {
+
+/*
+ * `to_string` Helpers
+ */
+
+void __to_string::operator()(ostream& __os, std::stacktrace_entry const& entry) {
+  // Although 64-bit addresses are 16 nibbles long, they're often <= 0x7fff_ffff_ffff
+  constexpr static int __k_addr_width = (sizeof(void*) > 4) ? 12 : 8;
+
+  __os << "0x" << std::hex << std::setfill('0') << std::setw(__k_addr_width) << entry.native_handle();
+  if (!entry.description().empty()) {
+    __os << ": " << entry.description();
+  }
+  if (!entry.source_file().empty()) {
+    __os << ": " << entry.source_file();
+  }
+  if (entry.source_line()) {
+    __os << ":" << std::dec << entry.source_line();
+  }
+}
+
+void __to_string::operator()(ostream& __os, std::stacktrace_entry const* __entries, size_t __count) {
+  /*
+   * Print each entry as a line, as per `operator()`, with additional whitespace
+   * at the start of the line, and only a newline added at the end:
+   *
+   *   frame   1: 0xbeefbeefbeef: _symbol_name: /path/to/file.cc:123
+   */
+  if (!__count) {
+    __os << "(empty stacktrace)";
+  } else {
+    for (size_t __i = 0; __i < __count; __i++) {
+      if (__i) {
+        // Insert newlines between entries (but not before the first or after the last)
+        __os << std::endl;
+      }
+      __os << "  frame " << std::setw(3) << std::setfill(' ') << std::dec << (__i + 1) << ": ";
+      (*this)(__os, __entries[__i]);
+    }
+  }
+}
+
+string __to_string::operator()(std::stacktrace_entry const& entry) {
+  stringstream __ss;
+  (*this)(__ss, entry);
+  return __ss.str();
+}
+
+string __to_string::operator()(std::stacktrace_entry const* __entries, size_t __count) {
+  stringstream __ss;
+  (*this)(__ss, __entries, __count);
+  return __ss.str();
+}
+
+} // namespace __stacktrace
+
+// `to_string`-related non-member functions
+
+_LIBCPP_EXPORTED_FROM_ABI string to_string(const stacktrace_entry& __entry) {
+  return __stacktrace::__to_string()(__entry);
+}
+
+_LIBCPP_EXPORTED_FROM_ABI ostream& operator<<(ostream& __os, const stacktrace_entry& __entry) {
+  __stacktrace::__to_string()(__os, __entry);
+  return __os;
+}
+
+_LIBCPP_END_NAMESPACE_STD
diff --git a/libcxx/src/experimental/stacktrace/tools/addr2line.cpp b/libcxx/src/experimental/stacktrace/tools/addr2line.cpp
new file mode 100644
index 0000000000000..310e99699569b
--- /dev/null
+++ b/libcxx/src/experimental/stacktrace/tools/addr2line.cpp
@@ -0,0 +1,100 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include <__config>
+#include <__config_site>
+#include <cstddef>
+#include <iostream>
+
+#include "tools.h"
+
+#include <experimental/__stacktrace/detail/context.h>
+#include <experimental/__stacktrace/detail/entry.h>
+#include <string>
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+namespace __stacktrace {
+
+std::pmr::list<std::pmr::string> addr2line::buildArgs(context& cx) const {
+  auto& alloc = cx.__alloc_;
+  auto ret    = alloc.new_string_list();
+  if (cx.__main_prog_path_.empty()) {
+    // Should not have reached here but be graceful anyway
+    ret.push_back("/bin/false");
+    return ret;
+  }
+
+  ret.push_back(progName_);
+  ret.push_back("--functions");
+  ret.push_back("--demangle");
+  ret.push_back("--basenames");
+  ret.push_back("--pretty-print"); // This "human-readable form" is easier to parse
+  ret.push_back("-e");
+  ret.push_back(cx.__main_prog_path_);
+  for (auto& entry : cx.__entries_) {
+    ret.push_back(alloc.hex_string(entry.__addr_unslid_));
+  }
+  return ret;
+}
+
+void addr2line::parseOutput(context& trace, entry& entry, std::istream& output) const {
+  // clang-format off
+/*
+Example:
+--
+llvm-addr2line -e foo --functions --demangle --basenames --pretty-print --no-inlines 0x11a0 0x1120 0x3d58 0x1284
+
+Output: (1 line per input address)
+--
+main at foo.cc:15
+register_tm_clones at crtstuff.c:0
+GCC_except_table2 at foo.cc:0
+test::Foo::Foo(int) at foo.cc:11
+*/
+  // clang-format on
+
+  std::pmr::string line{&trace.__alloc_};
+  std::getline(output, line);
+  while (isspace(line.back())) {
+    line.pop_back();
+  }
+  if (line.empty()) {
+    return;
+  }
+  // Split at the sequence " at ".  Barring weird symbols
+  // having " at " in them, this should work.
+  auto sepIndex = line.find(" at ");
+  if (sepIndex == std::string::npos) {
+    return;
+  }
+  if (sepIndex > 0) {
+    entry.__desc_ = line.substr(0, sepIndex);
+  }
+  auto fileBegin = sepIndex + 4;
+  if (fileBegin >= line.size()) {
+    return;
+  }
+  auto fileline = line.substr(fileBegin);
+  auto colon    = fileline.find_last_of(":");
+  if (colon > 0 && !fileline.starts_with("?")) {
+    entry.__file_ = fileline.substr(0, colon);
+  }
+
+  if (colon == std::string::npos) {
+    return;
+  }
+  uint32_t lineno = 0;
+  auto pos        = colon;
+  while (isdigit(fileline[++pos])) {
+    lineno = lineno * 10 + (fileline[pos] - '0');
+  }
+  entry.__line_ = lineno;
+}
+
+} // namespace __stacktrace
+_LIBCPP_END_NAMESPACE_STD
diff --git a/libcxx/src/experimental/stacktrace/tools/atos.cpp b/libcxx/src/experimental/stacktrace/tools/atos.cpp
new file mode 100644
index 0000000000000..569883a4b12bc
--- /dev/null
+++ b/libcxx/src/experimental/stacktrace/tools/atos.cpp
@@ -0,0 +1,115 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include <__config>
+#include <__config_site>
+#include <cstddef>
+#include <istream>
+#include <string>
+#include <unistd.h>
+
+#include "tools.h"
+
+#include <experimental/__stacktrace/detail/alloc.h>
+#include <experimental/__stacktrace/detail/context.h>
+#include <experimental/__stacktrace/detail/entry.h>
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+namespace __stacktrace {
+
+std::pmr::list<std::pmr::string> atos::buildArgs(context& cx) const {
+  auto& alloc = cx.__alloc_;
+  auto ret    = alloc.new_string_list();
+  ret.push_back(progName_);
+  ret.push_back("-p");
+  ret.push_back(alloc.u64_string(getpid()));
+  // TODO(stackcx23): Allow options in env, e.g. LIBCPP_STACKTRACE_OPTIONS=FullPath
+  // ret.push_back("--fullPath");
+  for (auto& entry : cx.__entries_) {
+    ret.push_back(alloc.hex_string(entry.__addr_));
+  }
+  return ret;
+}
+
+void atos::parseOutput(context& cx, entry& entry, std::istream& output) const {
+  // Simple example:
+  //
+  //   main (in testprog) (/Users/steve/code/notes/testprog.cc:208)
+  //
+  // Assuming this is always atos's format (except when it returns empty lines)
+  // we can split the string like so:
+  //
+  //   main (in testprog) (/Users/steve/code/notes/testprog.cc:208)
+  //   ^^^^-----^^^^^^^^---^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^-^^^-
+  //   sym      module     filename                            line
+  //
+  // Note that very strange filenames or module names can confuse this.
+  // We'll do the best we can for a decent result, while definitely ensuring safety
+  // (i.e. careful with our bound-checking).
+  //
+  // Another more interesting example (with an added newline for legibility):
+  //
+  //   std::__1::basic_ios<char, std::__1::char_traits<char>>::fill[abi:ne190107]() const (in testprog)
+  //   (/opt/homebrew/Cellar/llvm/19.1.7_1/bin/../include/c++/v1/ios:0
+  //
+  // If this more or less fits our expected format we'll take these data,
+  // even if the line number is 0.
+
+  auto line = cx.__alloc_.new_string(256);
+  std::getline(output, line);
+  while (isspace(line.back())) {
+    line.pop_back();
+  }
+  if (line.empty()) {
+    return;
+  }
+  auto buf  = line.data();
+  auto size = line.size();
+
+  auto* end    = buf + size;
+  auto* symEnd = strstr(buf, " (in ");
+  if (!symEnd) {
+    return;
+  }
+  auto* modBegin = symEnd + 5;
+  auto* modEnd   = strstr(modBegin, ") (");
+  if (!modEnd) {
+    return;
+  }
+  auto* fileBegin = modEnd + 3; // filename starts just after that
+  if (fileBegin >= end) {
+    return;
+  }
+  auto const* lastColon = fileBegin; // we'll search for last colon after filename
+  char const* nextColon;
+  while ((nextColon = strstr(lastColon + 1, ":"))) { // skip colons in filename (e.g. in "C:\foo.cpp")
+    lastColon = nextColon;
+  }
+
+  std::string_view sym{buf, size_t(symEnd - buf)};
+  // In case a previous step could not obtain the symbol name,
+  // we have the name provided by atos; only use that if we have no symbol
+  // (no need to copy more strings otherwise).
+  if (entry.__desc_.empty() && !sym.empty()) {
+    entry.__desc_ = sym;
+  }
+
+  std::string_view file{fileBegin, size_t(lastColon - fileBegin)};
+  if (file != "?" && file != "??" && !file.empty()) {
+    entry.__file_ = file;
+  }
+
+  unsigned lineno = 0;
+  for (auto* digit = lastColon + 1; digit < end && isdigit(*digit); ++digit) {
+    lineno = (lineno * 10) + unsigned(*digit - '0');
+  }
+  entry.__line_ = lineno;
+}
+
+} // namespace __stacktrace
+_LIBCPP_END_NAMESPACE_STD
diff --git a/libcxx/src/experimental/stacktrace/tools/llvm_symbolizer.cpp b/libcxx/src/experimental/stacktrace/tools/llvm_symbolizer.cpp
new file mode 100644
index 0000000000000..0a9907978dcf2
--- /dev/null
+++ b/libcxx/src/experimental/stacktrace/tools/llvm_symbolizer.cpp
@@ -0,0 +1,112 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include <__config>
+#include <__config_site>
+#include <cstddef>
+#include <iostream>
+#include <string_view>
+
+#include "../common/debug.h"
+#include "tools.h"
+
+#include <experimental/__stacktrace/detail/context.h>
+#include <experimental/__stacktrace/detail/entry.h>
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+namespace __stacktrace {
+
+// TODO(stacktrace23): possible to link against `libLLVMSymbolize.a`, or some shared obj at runtime (does that exist?)
+
+std::pmr::list<std::pmr::string> llvm_symbolizer::buildArgs(context& cx) const {
+  auto& alloc = cx.__alloc_;
+  auto ret    = alloc.new_string_list();
+  ret.push_back(progName_);
+  ret.push_back("--demangle");
+  ret.push_back("--no-inlines");
+  ret.push_back("--verbose");
+  ret.push_back("--relativenames");
+  ret.push_back("--functions=short");
+  for (auto& entry : cx.__entries_) {
+    auto addr_string = alloc.hex_string(entry.__addr_unslid_);
+    debug() << "@@@ " << addr_string << " " << entry.__file_ << " " << entry.__file_.empty() << '\n';
+    if (!entry.__file_.empty()) {
+      auto arg = alloc.new_string(entry.__file_.size() + 40);
+      arg += "FILE:";
+      arg += entry.__file_;
+      arg += " ";
+      arg += addr_string;
+      ret.push_back(arg);
+    } else {
+      ret.push_back(addr_string);
+    }
+  }
+  return ret;
+}
+
+void llvm_symbolizer::parseOutput(context& cx, entry& entry, std::istream& output) const {
+  // clang-format off
+/*
+With "--verbose", parsing is a little easier, or at least, more reliable;
+probably the best solution (until we have a JSON parser).
+Example output, verbatim, between the '---' lines:
+---
+test1<test_alloc<std::__1::stacktrace_entry> >
+  Filename: /data/code/llvm-project/libcxx/test/std/diagnostics/stacktrace/basic.cons.pass.cpp
+  Function start filename: /data/code/llvm-project/libcxx/test/std/diagnostics/stacktrace/basic.cons.pass.cpp
+  Function start line: 114
+  Function start address: 0x8dd0
+  Line: 116
+  Column: 14
+
+---
+Note that this includes an extra empty line as a terminator.
+*/
+  // clang-format on
+
+  auto& alloc = cx.__alloc_;
+  auto line   = alloc.new_string(256);
+  std::string_view tmp;
+  while (true) {
+    std::getline(output, line);
+    while (isspace(line.back())) {
+      line.pop_back();
+    }
+    if (line.empty()) {
+      return;
+    }
+    if (!line.starts_with("  ")) {
+      // The symbol has no leading whitespace, while the other
+      // lines with "fields" like line, column, filename, etc.
+      // start with two spaces.
+      if (line != "??") {
+        entry.__desc_ = line;
+      }
+    } else if (line.starts_with("  Filename:")) {
+      tmp = line;
+      tmp = tmp.substr(tmp.find_first_of(":") + 2); // skip ": "
+      if (tmp != "??") {
+        entry.__file_ = tmp;
+      }
+    } else if (line.starts_with("  Line:")) {
+      tmp = line;
+      tmp = tmp.substr(tmp.find_first_of(":") + 2); // skip ": "
+      if (tmp != "??" && tmp != "0") {
+        uint32_t lineno = 0;
+        auto pos        = 0;
+        while (isdigit(tmp[pos])) {
+          lineno = lineno * 10 + (tmp[pos++] - '0');
+        }
+        entry.__line_ = lineno;
+      }
+    }
+  }
+}
+
+} // namespace __stacktrace
+_LIBCPP_END_NAMESPACE_STD
diff --git a/libcxx/src/experimental/stacktrace/tools/pspawn.h b/libcxx/src/experimental/stacktrace/tools/pspawn.h
new file mode 100644
index 0000000000000..906a504441368
--- /dev/null
+++ b/libcxx/src/experimental/stacktrace/tools/pspawn.h
@@ -0,0 +1,163 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef _LIBCPP_STACKTRACE_PSPAWN_H
+#define _LIBCPP_STACKTRACE_PSPAWN_H
+
+#include "../common/config.h"
+
+#if defined(_LIBCPP_STACKTRACE_CAN_SPAWN_TOOLS)
+
+#  include <__config>
+#  include <__config_site>
+#  include <cassert>
+#  include <cerrno>
+#  include <csignal>
+#  include <cstddef>
+#  include <cstdlib>
+#  include <list>
+#  include <spawn.h>
+#  include <string>
+#  include <sys/fcntl.h>
+#  include <sys/types.h>
+#  include <sys/wait.h>
+#  include <unistd.h>
+#  include <vector>
+
+#  include <experimental/__stacktrace/detail/context.h>
+#  include <experimental/__stacktrace/detail/entry.h>
+
+#  include "../common/debug.h"
+#  include "../common/failed.h"
+#  include "../common/fd.h"
+#  include "tools.h"
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+namespace __stacktrace {
+
+struct file_actions {
+  posix_spawn_file_actions_t fa_;
+
+  file_actions() {
+    if (posix_spawn_file_actions_init(&fa_)) {
+      throw failed("posix_spawn_file_actions_init", errno);
+    }
+  }
+
+  ~file_actions() { posix_spawn_file_actions_destroy(&fa_); }
+
+  void addClose(int fd) {
+    if (posix_spawn_file_actions_addclose(&fa_, fd)) {
+      throw failed("posix_spawn_file_actions_addclose", errno);
+    }
+  }
+  void addDup2(int fd, int stdfd) {
+    if (posix_spawn_file_actions_adddup2(&fa_, fd, stdfd)) {
+      throw failed("posix_spawn_file_actions_adddup2", errno);
+    }
+  }
+
+  fd redirectOutFD() {
+    int fds[2];
+    if (::pipe(fds)) {
+      throw failed("pipe", errno);
+    }
+    addClose(fds[0]);
+    addDup2(fds[1], 1);
+    return {fds[0]};
+  }
+
+  void redirectInNull() { addDup2(fd::null_fd(), 0); }
+  void redirectOutNull() { addDup2(fd::null_fd(), 1); }
+  void redirectErrNull() { addDup2(fd::null_fd(), 2); }
+};
+
+struct pspawn {
+  tool const& tool_;
+  pid_t pid_{0};
+  file_actions fa_{};
+
+  // TODO(stacktrace23): ignore SIGCHLD for spawned subprocess
+
+  ~pspawn() {
+    if (pid_) {
+      kill(pid_, SIGTERM);
+      wait();
+    }
+  }
+
+  void spawn(std::pmr::list<std::pmr::string> const& argStrings) {
+    std::pmr::vector<char const*> argv{argStrings.get_allocator()};
+    argv.reserve(argStrings.size() + 1);
+    for (auto const& str : argStrings) {
+      argv.push_back(str.data());
+    }
+    argv.push_back(nullptr);
+    int err;
+    if ((err = posix_spawnp(&pid_, argv[0], &fa_.fa_, nullptr, const_cast<char**>(argv.data()), nullptr))) {
+      throw failed("posix_spawnp", err);
+    }
+  }
+
+  int wait() {
+    int status;
+    waitpid(pid_, &status, 0);
+    return status;
+  }
+};
+
+struct pspawn_tool : pspawn {
+  context& cx_;
+  fd fd_;
+  fd_streambuf buf_;
+  fd_istream stream_;
+
+  pspawn_tool(tool const& a2l, context& cx, char* buf, size_t size)
+      : pspawn{a2l}, cx_(cx), fd_(fa_.redirectOutFD()), buf_(fd_, buf, size), stream_(buf_) {
+    if (!debug::enabled()) {
+      fa_.redirectErrNull();
+    }
+    fa_.redirectInNull();
+  }
+
+  void run() {
+    // Cannot run "addr2line" or similar without addresses, since we
+    // provide them in argv, and if there are none passed in argv, the
+    // tool will try to read from stdin and hang.
+    if (cx_.__entries_.empty()) {
+      return;
+    }
+
+    auto argStrings = tool_.buildArgs(cx_);
+    if (debug::enabled()) {
+      debug() << "Trying to get stacktrace using:";
+      for (auto& str : argStrings) {
+        debug() << " \"" << str << '"';
+      }
+      debug() << '\n';
+    }
+
+    spawn(argStrings);
+
+    for (auto& entry : cx_.__entries_) {
+      tool_.parseOutput(cx_, entry, stream_);
+    }
+  }
+};
+
+struct spawner {
+  context& cx_;
+  void resolve_lines();
+};
+
+} // namespace __stacktrace
+_LIBCPP_END_NAMESPACE_STD
+
+#endif
+
+#endif // _LIBCPP_STACKTRACE_PSPAWN_H
diff --git a/libcxx/src/experimental/stacktrace/tools/tools.h b/libcxx/src/experimental/stacktrace/tools/tools.h
new file mode 100644
index 0000000000000..d832974e69cbb
--- /dev/null
+++ b/libcxx/src/experimental/stacktrace/tools/tools.h
@@ -0,0 +1,65 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef _LIBCPP_STACKTRACE_TOOLS_H
+#define _LIBCPP_STACKTRACE_TOOLS_H
+
+#include <__config>
+#include <__config_site>
+#include <cassert>
+#include <cstddef>
+#include <list>
+#include <string>
+
+#include <experimental/__stacktrace/detail/context.h>
+#include <experimental/__stacktrace/detail/entry.h>
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+namespace __stacktrace {
+
+struct tool {
+  char const* progName_;
+  explicit tool(char const* progName) : progName_(progName) {}
+  constexpr virtual ~tool() = default;
+
+  /** Construct complete `argv` for the spawned process.
+  Includes the program name at argv[0], followed by flags */
+  virtual std::pmr::list<std::pmr::string> buildArgs(context& trace) const = 0;
+
+  /** Parse line(s) output by the tool, and modify `entry`. */
+  virtual void parseOutput(context& trace, entry& e, std::istream& output) const = 0;
+};
+
+struct llvm_symbolizer : tool {
+  constexpr virtual ~llvm_symbolizer() = default;
+  llvm_symbolizer() : llvm_symbolizer("llvm-symbolizer") {}
+  explicit llvm_symbolizer(char const* progName) : tool{progName} {}
+  std::pmr::list<std::pmr::string> buildArgs(context& trace) const override;
+  void parseOutput(context& trace, entry& entry, std::istream& output) const override;
+};
+
+struct addr2line : tool {
+  constexpr virtual ~addr2line() = default;
+  addr2line() : addr2line("addr2line") {}
+  explicit addr2line(char const* progName) : tool{progName} {}
+  std::pmr::list<std::pmr::string> buildArgs(context& trace) const override;
+  void parseOutput(context& trace, entry& e, std::istream& stream) const override;
+};
+
+struct atos : tool {
+  constexpr virtual ~atos() = default;
+  atos() : atos("atos") {}
+  explicit atos(char const* progName) : tool{progName} {}
+  std::pmr::list<std::pmr::string> buildArgs(context& trace) const override;
+  void parseOutput(context& trace, entry& entry, std::istream& output) const override;
+};
+
+} // namespace __stacktrace
+_LIBCPP_END_NAMESPACE_STD
+
+#endif // _LIBCPP_STACKTRACE_TOOLS_H
diff --git a/libcxx/src/experimental/stacktrace/tools/toolspawner.cpp b/libcxx/src/experimental/stacktrace/tools/toolspawner.cpp
new file mode 100644
index 0000000000000..05a2f8e6c2eb4
--- /dev/null
+++ b/libcxx/src/experimental/stacktrace/tools/toolspawner.cpp
@@ -0,0 +1,185 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "../common/config.h"
+
+#if defined(_LIBCPP_STACKTRACE_CAN_SPAWN_TOOLS)
+
+#  include <__config>
+#  include <__config_site>
+#  include <cassert>
+#  include <cerrno>
+#  include <csignal>
+#  include <cstddef>
+#  include <cstdlib>
+#  include <spawn.h>
+#  include <string>
+#  include <sys/fcntl.h>
+#  include <sys/types.h>
+#  include <sys/wait.h>
+#  include <unistd.h>
+
+#  include "../common/failed.h"
+#  include "pspawn.h"
+
+#  include <experimental/__stacktrace/detail/entry.h>
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+namespace __stacktrace {
+
+namespace {
+
+/**
+Returns a list of `tool` objects that can be tried during the first stacktrace operation.
+The result is an array of `tool*` pointers with a final `nullptr` terminator.
+
+The returned tool array pointer is saved during `resolve_lines`'s static init,
+with the first working tool being used from that point forward.
+
+This will first add any tools specified by these defines (in order):
+- LIBCXX_STACKTRACE_FORCE_LLVM_SYMBOLIZER_PATH
+- LIBCXX_STACKTRACE_FORCE_GNU_ADDR2LINE_PATH
+- LIBCXX_STACKTRACE_FORCE_APPLE_ATOS_PATH
+
+Then any tools specified by the environment variables of the same names (and added in the same order).
+
+Finally, this adds the tools `llvm-symbolizer`, `addr2line`, and `atos`, in that order.
+These tools won't have absolute paths, so $PATH will be searched for these.
+
+Called by `findWorkingTool` during its static initialization, therefore this is used in a threadsafe way.
+*/
+tool const** toolList() {
+  constexpr static size_t kMax = 20;
+  static tool const* array_[kMax];
+  size_t count = 0;
+
+  auto add = [&](tool* t) {
+    assert(count < kMax - 1);
+    array_[count++] = t;
+  };
+
+#  define STRINGIFY0(x) #x
+#  define STRINGIFY(x) STRINGIFY0(x)
+
+#  if defined(LIBCXX_STACKTRACE_FORCE_LLVM_SYMBOLIZER_PATH)
+  {
+    static llvm_symbolizer t{STRINGIFY(LIBCXX_STACKTRACE_FORCE_LLVM_SYMBOLIZER_PATH)};
+    add(&t);
+  }
+#  endif
+#  if defined(LIBCXX_STACKTRACE_FORCE_GNU_ADDR2LINE_PATH)
+  {
+    static addr2line t{STRINGIFY(LIBCXX_STACKTRACE_FORCE_GNU_ADDR2LINE_PATH)};
+    add(&t);
+  }
+#  endif
+#  if defined(LIBCXX_STACKTRACE_FORCE_APPLE_ATOS_PATH)
+  {
+    static atos t{STRINGIFY(LIBCXX_STACKTRACE_FORCE_APPLE_ATOS_PATH)};
+    add(&t);
+  }
+#  endif
+
+  if (getenv("LIBCXX_STACKTRACE_FORCE_LLVM_SYMBOLIZER_PATH")) {
+    static llvm_symbolizer t{getenv("LIBCXX_STACKTRACE_FORCE_LLVM_SYMBOLIZER_PATH")};
+    add(&t);
+  }
+  if (getenv("LIBCXX_STACKTRACE_FORCE_GNU_ADDR2LINE_PATH")) {
+    static addr2line t{getenv("LIBCXX_STACKTRACE_FORCE_GNU_ADDR2LINE_PATH")};
+    add(&t);
+  }
+  if (getenv("LIBCXX_STACKTRACE_FORCE_APPLE_ATOS_PATH")) {
+    static atos t{getenv("LIBCXX_STACKTRACE_FORCE_APPLE_ATOS_PATH")};
+    add(&t);
+  }
+
+  {
+    static llvm_symbolizer t;
+    add(&t);
+  }
+  {
+    static addr2line t;
+    add(&t);
+  }
+  {
+    static atos t;
+    add(&t);
+  }
+
+  array_[count] = nullptr; // terminator
+  return array_;
+}
+
+// Try a handful of different addr2line-esque tools, returning the first discovered, or else nullptr
+tool const* findWorkingTool(auto& trace) {
+  // Try each of these programs and stop at the first one that works.
+  // There's no synchronization so this is subject to races on setting `prog`,
+  // but as long as one thread ends up setting it to something that works, we're good.
+  // Programs to try ($PATH is searched):
+  auto* it = toolList();
+  tool const* prog;
+  while ((prog = *it++)) {
+    pspawn test{*prog}; // Just try to run with "--help"
+    try {
+      std::pmr::list<std::pmr::string> testArgs{&trace.__alloc_};
+      testArgs.push_back(prog->progName_);
+      testArgs.push_back("--help");
+      test.fa_.redirectInNull();
+      test.fa_.redirectOutNull();
+      test.fa_.redirectErrNull();
+      test.spawn(testArgs);
+      if (test.wait() == 0) {
+        // Success
+        return prog;
+      }
+    } catch (failed const&) {
+      /* ignore during probe attempt */
+    }
+  }
+  return nullptr;
+}
+
+} // namespace
+
+void spawner::resolve_lines() {
+  // The address-to-line tool that worked (after lazy-setting, below)
+  static tool const* prog{nullptr};
+  // Whether we should not attempt because tool detection previously failed.
+  static bool fail{false};
+
+  // If this previously failed, don't try again.
+  if (fail) {
+    return;
+  }
+
+  if (!prog) {
+    prog = findWorkingTool(cx_);
+    if (!prog) {
+      fail = true;
+      return;
+    }
+  }
+  assert(prog);
+
+  char buf[256];
+  pspawn_tool proc(*prog, cx_, buf, sizeof(buf));
+  try {
+    proc.run();
+  } catch (failed const& failed) {
+    debug() << failed.what();
+    if (failed.errno_) {
+      debug() << " (" << failed.errno_ << " " << strerror(failed.errno_) << ')';
+    }
+    debug() << '\n';
+  }
+}
+
+} // namespace __stacktrace
+_LIBCPP_END_NAMESPACE_STD
+
+#endif
diff --git a/libcxx/src/experimental/stacktrace/unwind/unwind.cpp b/libcxx/src/experimental/stacktrace/unwind/unwind.cpp
new file mode 100644
index 0000000000000..a316306bc43eb
--- /dev/null
+++ b/libcxx/src/experimental/stacktrace/unwind/unwind.cpp
@@ -0,0 +1,60 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "../common/config.h"
+
+#if defined(_LIBCPP_STACKTRACE_COLLECT_UNWIND)
+
+#  include "./unwind.h"
+
+#  include <experimental/__stacktrace/detail/context.h>
+#  include <experimental/__stacktrace/detail/entry.h>
+#  include <unwind.h>
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+namespace __stacktrace {
+
+struct unwind_backtrace {
+  context& cx_;
+  size_t skip_;
+  size_t maxDepth_;
+
+  _Unwind_Reason_Code callback(_Unwind_Context* ucx) {
+    if (skip_) {
+      --skip_;
+      return _Unwind_Reason_Code::_URC_NO_REASON;
+    }
+    if (!maxDepth_) {
+      return _Unwind_Reason_Code::_URC_NORMAL_STOP;
+    }
+    --maxDepth_;
+    int ipBefore;
+    auto ip = _Unwind_GetIPInfo(ucx, &ipBefore);
+    if (!ip) {
+      return _Unwind_Reason_Code::_URC_NORMAL_STOP;
+    }
+    auto& entry          = cx_.__entries_.emplace_back();
+    entry.__addr_        = (ipBefore ? ip : ip - 1);
+    entry.__addr_unslid_ = entry.__addr_; // in case we can't un-slide
+    return _Unwind_Reason_Code::_URC_NO_REASON;
+  }
+
+  static _Unwind_Reason_Code callback(_Unwind_Context* cx, void* self) {
+    return ((unwind_backtrace*)self)->callback(cx);
+  }
+};
+
+_LIBCPP_NO_TAIL_CALLS _LIBCPP_NOINLINE void unwind::collect(size_t skip, size_t max_depth) {
+  unwind_backtrace bt{cx_, skip + 1, max_depth}; // skip this call as well
+  _Unwind_Backtrace(unwind_backtrace::callback, &bt);
+}
+
+} // namespace __stacktrace
+_LIBCPP_END_NAMESPACE_STD
+
+#endif
diff --git a/libcxx/src/experimental/stacktrace/unwind/unwind.h b/libcxx/src/experimental/stacktrace/unwind/unwind.h
new file mode 100644
index 0000000000000..1b099e3a0b922
--- /dev/null
+++ b/libcxx/src/experimental/stacktrace/unwind/unwind.h
@@ -0,0 +1,30 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef _LIBCPP_STACKTRACE_UNWIND_H
+#define _LIBCPP_STACKTRACE_UNWIND_H
+
+#include <__config>
+#include <__config_site>
+#include <cstddef>
+#include <cstdlib>
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+namespace __stacktrace {
+
+struct _LIBCPP_HIDE_FROM_ABI context;
+
+struct unwind {
+  context& cx_;
+  void collect(size_t skip, size_t max_depth);
+};
+
+} // namespace __stacktrace
+_LIBCPP_END_NAMESPACE_STD
+
+#endif // _LIBCPP_STACKTRACE_UNWIND_H
diff --git a/libcxx/src/experimental/stacktrace/windows/dbghelp_dll.cpp b/libcxx/src/experimental/stacktrace/windows/dbghelp_dll.cpp
new file mode 100644
index 0000000000000..274c9ecb2b314
--- /dev/null
+++ b/libcxx/src/experimental/stacktrace/windows/dbghelp_dll.cpp
@@ -0,0 +1,56 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "../common/config.h"
+
+#if defined(_LIBCPP_STACKTRACE_WINDOWS)
+
+// windows.h must be first
+#  include <windows.h>
+// other windows-specific headers
+#  include <dbghelp.h>
+#  define PSAPI_VERSION 1
+#  include <psapi.h>
+// standard headers
+#  include <cstdlib>
+#  include <mutex>
+
+#  include "dll.h"
+#  include <experimental/__stacktrace/detail/entry.h>
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+namespace __stacktrace {
+
+dbghelp_dll::~dbghelp_dll() = default;
+
+dbghelp_dll& dbghelp_dll::get() {
+  dbghelp_dll ret;
+  return ret;
+}
+
+dbghelp_dll::dbghelp_dll() : dll("dbghelp.dll") {
+  // clang-format off
+if (!get_func(&ImageNtHeader, "ImageNtHeader")) { return; }
+  if (!get_func(&StackWalk64, "StackWalk64")) { return; }
+  if (!get_func(&SymCleanup, "SymCleanup")) { return; }
+  if (!get_func(&SymFunctionTableAccess64, "SymFunctionTableAccess64")) { return; }
+  if (!get_func(&SymGetLineFromAddr64, "SymGetLineFromAddr64")) { return; }
+  if (!get_func(&SymGetModuleBase64, "SymGetModuleBase64")) { return; }
+  if (!get_func(&SymGetOptions, "SymGetOptions")) { return; }
+  if (!get_func(&SymGetSymFromAddr64, "SymGetSymFromAddr64")) { return; }
+  if (!get_func(&SymInitialize, "SymInitialize")) { return; }
+  if (!get_func(&SymLoadModule64, "SymLoadModule64")) { return; }
+  if (!get_func(&SymSetOptions, "SymSetOptions")) { return; }
+  valid_ = true;
+  // clang-format on
+}
+
+} // namespace __stacktrace
+_LIBCPP_END_NAMESPACE_STD
+
+#endif // _LIBCPP_STACKTRACE_USE_DBGHELP
diff --git a/libcxx/src/experimental/stacktrace/windows/dbghelp_dll.h b/libcxx/src/experimental/stacktrace/windows/dbghelp_dll.h
new file mode 100644
index 0000000000000..920391fb9ba52
--- /dev/null
+++ b/libcxx/src/experimental/stacktrace/windows/dbghelp_dll.h
@@ -0,0 +1,71 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef _LIBCPP_STACKTRACE_WINDOWS_DBGHELP_DLL_H
+#define _LIBCPP_STACKTRACE_WINDOWS_DBGHELP_DLL_H
+
+#include "../common/config.h"
+
+#if defined(_LIBCPP_STACKTRACE_WINDOWS)
+// windows.h must be first
+#  include <windows.h>
+// other windows-specific headers
+#  include <dbghelp.h>
+#  define PSAPI_VERSION 1
+#  include <psapi.h>
+// standard headers
+#  include <cstdlib>
+#  include <mutex>
+
+#  include <experimental/__stacktrace/detail/entry.h>
+
+#  include "../common/debug.h"
+#  include "dll.h"
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+namespace __stacktrace {
+
+// clang-format off
+
+struct dbghelp_dll final : dll {
+  virtual ~dbghelp_dll() = default;
+  static dbghelp_dll& get() { static dbghelp_dll ret; return ret; }
+
+  IMAGE_NT_HEADERS* (*ImageNtHeader)(void*);
+  bool    (*StackWalk64)        (DWORD, HANDLE, HANDLE, STACKFRAME64*, void*, void*, void*, void*, void*);
+  bool    (*SymCleanup)         (HANDLE);
+  void*   (*SymFunctionTableAccess64)(HANDLE, DWORD64);
+  bool    (*SymGetLineFromAddr64)(HANDLE, DWORD64, DWORD*, IMAGEHLP_LINE64*);
+  DWORD64 (*SymGetModuleBase64) (HANDLE, DWORD64);
+  DWORD   (*SymGetOptions)      ();
+  bool    (*SymGetSymFromAddr64)(HANDLE, DWORD64, DWORD64*, IMAGEHLP_SYMBOL64*);
+  bool    (*SymInitialize)      (HANDLE, char const*, bool);
+  DWORD64 (*SymLoadModule64)    (HANDLE, HANDLE, char const*, char const*, void*, DWORD);
+  DWORD   (*SymSetOptions)      (DWORD);
+
+  dbghelp_dll() : dll("dbghelp.dll") {
+    if (!get_func(&ImageNtHeader, "ImageNtHeader")) { return; }
+    if (!get_func(&StackWalk64, "StackWalk64")) { return; }
+    if (!get_func(&SymCleanup, "SymCleanup")) { return; }
+    if (!get_func(&SymFunctionTableAccess64, "SymFunctionTableAccess64")) { return; }
+    if (!get_func(&SymGetLineFromAddr64, "SymGetLineFromAddr64")) { return; }
+    if (!get_func(&SymGetModuleBase64, "SymGetModuleBase64")) { return; }
+    if (!get_func(&SymGetOptions, "SymGetOptions")) { return; }
+    if (!get_func(&SymGetSymFromAddr64, "SymGetSymFromAddr64")) { return; }
+    if (!get_func(&SymInitialize, "SymInitialize")) { return; }
+    if (!get_func(&SymLoadModule64, "SymLoadModule64")) { return; }
+    if (!get_func(&SymSetOptions, "SymSetOptions")) { return; }
+    valid_ = true;
+  }
+};
+
+} // namespace __stacktrace
+_LIBCPP_END_NAMESPACE_STD
+
+#endif // _LIBCPP_STACKTRACE_WINDOWS
+#endif // _LIBCPP_STACKTRACE_WINDOWS_DBGHELP_DLL_H
diff --git a/libcxx/src/experimental/stacktrace/windows/dll.cpp b/libcxx/src/experimental/stacktrace/windows/dll.cpp
new file mode 100644
index 0000000000000..55fd729a9caf4
--- /dev/null
+++ b/libcxx/src/experimental/stacktrace/windows/dll.cpp
@@ -0,0 +1,40 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "../common/config.h"
+
+#if defined(_LIBCPP_STACKTRACE_WINDOWS)
+
+// windows.h must be first
+#  include <windows.h>
+// other windows-specific headers
+#  include <dbghelp.h>
+#  define PSAPI_VERSION 1
+#  include <psapi.h>
+// standard headers
+#  include <cstdlib>
+#  include <mutex>
+
+#  include "dll.h"
+#  include <experimental/__stacktrace/detail/entry.h>
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+namespace __stacktrace {
+
+dll::~dll() { FreeLibrary(module_); }
+
+dll::dll(char const* name) : name_(name), module_(LoadLibrary(name)) {
+  if (!module_) {
+    debug() << "LoadLibrary failed: " << name_ << ": " << GetLastError() << '\n';
+  }
+}
+
+} // namespace __stacktrace
+_LIBCPP_END_NAMESPACE_STD
+
+#endif // _LIBCPP_STACKTRACE_USE_DBGHELP
diff --git a/libcxx/src/experimental/stacktrace/windows/dll.h b/libcxx/src/experimental/stacktrace/windows/dll.h
new file mode 100644
index 0000000000000..ab363ce2c2561
--- /dev/null
+++ b/libcxx/src/experimental/stacktrace/windows/dll.h
@@ -0,0 +1,68 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef _LIBCPP_STACKTRACE_WINDOWS_DLL_H
+#define _LIBCPP_STACKTRACE_WINDOWS_DLL_H
+
+#include "../common/config.h"
+
+#if defined(_LIBCPP_STACKTRACE_WINDOWS)
+// windows.h must be first
+#  include <windows.h>
+// other windows-specific headers
+#  include <dbghelp.h>
+#  define PSAPI_VERSION 1
+#  include <psapi.h>
+// standard headers
+#  include <cstdlib>
+#  include <mutex>
+
+#  include <experimental/__stacktrace/detail/entry.h>
+
+#  include "../common/debug.h"
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+namespace __stacktrace {
+
+// clang-format off
+
+struct dll {
+  char const* name_;
+  HMODULE module_;
+  /** Set to true in subclass's ctor if initialized successfully. */
+  bool valid_{false};
+
+  operator bool() const { return valid_; }
+
+  explicit dll(char const* name)
+      : name_(name), module_(LoadLibrary(name)) {
+    if (!module_) {
+      debug() << "LoadLibrary failed: "
+              << name_ << ": " << GetLastError() << '\n';
+    }
+  }
+
+  virtual ~dll() { FreeLibrary(module_); }
+
+  template <typename F>
+  bool get_func(F* func, char const* name) {
+    if (!(*func = (F)GetProcAddress(module_, name))) {
+      debug() << "GetProcAddress failed: "
+              << name << "' (" << name_ << "): "
+              << GetLastError() << "\n";
+      return false;
+    }
+    return true;
+  }
+};
+
+} // namespace __stacktrace
+_LIBCPP_END_NAMESPACE_STD
+
+#endif // _LIBCPP_STACKTRACE_WINDOWS
+#endif // _LIBCPP_STACKTRACE_WINDOWS_DLL_H
diff --git a/libcxx/src/experimental/stacktrace/windows/psapi_dll.cpp b/libcxx/src/experimental/stacktrace/windows/psapi_dll.cpp
new file mode 100644
index 0000000000000..ab28df8d3fbd7
--- /dev/null
+++ b/libcxx/src/experimental/stacktrace/windows/psapi_dll.cpp
@@ -0,0 +1,48 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "../common/config.h"
+
+#if defined(_LIBCPP_STACKTRACE_WINDOWS)
+
+// windows.h must be first
+#  include <windows.h>
+// other windows-specific headers
+#  include <dbghelp.h>
+#  define PSAPI_VERSION 1
+#  include <psapi.h>
+// standard headers
+#  include <cstdlib>
+#  include <mutex>
+
+#  include "dll.h"
+#  include <experimental/__stacktrace/detail/entry.h>
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+namespace __stacktrace {
+
+psapi_dll::~psapi_dll() = default;
+
+psapi_dll& psapi_dll::get() {
+  psapi_dll ret;
+  return ret;
+}
+
+psapi_dll() : dll("psapi.dll") {
+  // clang-format off
+if (!getFunc(&EnumProcessModules, "EnumProcessModules")) { return; }
+  if (!getFunc(&GetModuleInformation, "GetModuleInformation")) { return; }
+  if (!getFunc(&GetModuleBaseName, "GetModuleBaseNameA")) { return; }
+  valid_ = true;
+  // clang-format on
+}
+
+} // namespace __stacktrace
+_LIBCPP_END_NAMESPACE_STD
+
+#endif // _LIBCPP_STACKTRACE_USE_DBGHELP
diff --git a/libcxx/src/experimental/stacktrace/windows/psapi_dll.h b/libcxx/src/experimental/stacktrace/windows/psapi_dll.h
new file mode 100644
index 0000000000000..4e6a192f3d790
--- /dev/null
+++ b/libcxx/src/experimental/stacktrace/windows/psapi_dll.h
@@ -0,0 +1,55 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef _LIBCPP_STACKTRACE_WINDOWS_PSAPI_DLL_H
+#define _LIBCPP_STACKTRACE_WINDOWS_PSAPI_DLL_H
+
+#include "../common/config.h"
+
+#if defined(_LIBCPP_STACKTRACE_WINDOWS)
+// windows.h must be first
+#  include <windows.h>
+// other windows-specific headers
+#  include <dbghelp.h>
+#  define PSAPI_VERSION 1
+#  include <psapi.h>
+// standard headers
+#  include <cstdlib>
+#  include <mutex>
+
+#  include <experimental/__stacktrace/detail/entry.h>
+
+#  include "../common/debug.h"
+#  include "dll.h"
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+namespace __stacktrace {
+
+// clang-format off
+
+struct psapi_dll final : dll {
+  virtual ~psapi_dll() = default;
+  static psapi_dll& get() { static psapi_dll ret; return ret; }
+
+  bool  (*EnumProcessModules)   (HANDLE, HMODULE*, DWORD, DWORD*);
+  bool  (*GetModuleInformation) (HANDLE, HMODULE, MODULEINFO*, DWORD);
+  DWORD (*GetModuleBaseName)    (HANDLE, HMODULE, char**, DWORD);
+
+  psapi_dll() : dll("psapi.dll") {
+    if (!get_func(&EnumProcessModules, "EnumProcessModules")) { return; }
+    if (!get_func(&GetModuleInformation, "GetModuleInformation")) { return; }
+    if (!get_func(&GetModuleBaseName, "GetModuleBaseNameA")) { return; }
+    valid_ = true;
+  }
+};
+
+} // namespace __stacktrace
+_LIBCPP_END_NAMESPACE_STD
+
+#endif // _LIBCPP_STACKTRACE_WINDOWS
+#endif // _LIBCPP_STACKTRACE_WINDOWS_PSAPI_DLL_H
diff --git a/libcxx/src/experimental/stacktrace/windows/win_impl.cpp b/libcxx/src/experimental/stacktrace/windows/win_impl.cpp
new file mode 100644
index 0000000000000..7773d0d872816
--- /dev/null
+++ b/libcxx/src/experimental/stacktrace/windows/win_impl.cpp
@@ -0,0 +1,204 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "win_impl.h"
+
+#if defined(_LIBCPP_STACKTRACE_WINDOWS)
+
+// windows.h must be first
+#  include <windows.h>
+// other windows-specific headers
+#  include <dbghelp.h>
+#  define PSAPI_VERSION 1
+#  include <psapi.h>
+// standard headers
+#  include <cstdlib>
+#  include <mutex>
+
+#  include "dll.h"
+#  include <experimental/__stacktrace/detail/entry.h>
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+namespace __stacktrace {
+
+namespace {
+
+/*
+Global objects, shared among all threads and among all stacktrace operations.
+The `dbghelp` APIs are not safe to call concurrently (according to their docs)
+so we claim a lock in the `WinDebugAPIs` constructor.
+*/
+
+// Statically-initialized
+std::mutex gWindowsAPILock;
+DbgHelpDLL dbg;
+PSAPIDLL ps;
+
+// Initialized once, in first WinDebugAPIs construction;
+// protected by the above mutex.
+HANDLE proc;
+HMODULE exe;
+IMAGE_NT_HEADERS* ntHeaders;
+bool globalInitialized{false};
+
+// Globals used across invocations of the functions below.
+// Also guarded by the above mutex.
+bool symsInitialized{false};
+HMODULE moduleHandles[1024];
+size_t moduleCount; // 0 IFF module enumeration failed
+
+} // namespace
+
+win_impl::WinDebugAPIs(context& trace) : trace_(trace), guard_(gWindowsAPILock) {
+  if (!globalInitialized) {
+    // Cannot proceed without these DLLs:
+    if (!dbg) {
+      return;
+    }
+    if (!ps) {
+      return;
+    }
+    proc = GetCurrentProcess();
+    if (!(exe = GetModuleHandle(nullptr))) {
+      return;
+    }
+    if (!(ntHeaders = (*dbg.ImageNtHeader)(exe))) {
+      return;
+    }
+
+    globalInitialized = true;
+  }
+
+  // Initialize symbol machinery.
+  // Presumably the symbols in this process's space can change between
+  // stacktraces, so we'll do this each time we take a trace.
+  // The final `true` means we want the runtime to enumerate all this
+  // process's modules' symbol tables.
+  symsInitialized  = (*dbg.SymInitialize)(proc, nullptr, true);
+  DWORD symOptions = (*dbg.SymGetOptions)();
+  symOptions |= SYMOPT_LOAD_LINES | SYMOPT_UNDNAME;
+  (*dbg.SymSetOptions)(symOptions);
+}
+
+win_impl::~WinDebugAPIs() {
+  if (symsInitialized) {
+    (*dbg.SymCleanup)(proc);
+    symsInitialized = false;
+  }
+}
+
+void win_impl::ident_modules() {
+  if (!globalInitialized) {
+    return;
+  }
+  DWORD needBytes;
+  auto enumMods = (*ps.EnumProcessModules)(proc, moduleHandles, sizeof(moduleHandles), LPDWORD(&needBytes));
+  if (enumMods) {
+    moduleCount = needBytes / sizeof(HMODULE);
+  } else {
+    moduleCount = 0;
+    Debug() << "EnumProcessModules failed: " << GetLastError() << '\n';
+  }
+}
+
+void win_impl::symbolize() {
+  // Very long symbols longer than this amount will be truncated.
+  static constexpr size_t kMaxSymName = 256;
+  if (!globalInitialized) {
+    return;
+  }
+
+  for (auto& entry : cx_.__entries_) {
+    char space[sizeof(IMAGEHLP_SYMBOL64) + kMaxSymName];
+    auto* sym          = (IMAGEHLP_SYMBOL64*)space;
+    sym->SizeOfStruct  = sizeof(IMAGEHLP_SYMBOL64);
+    sym->MaxNameLength = kMaxSymName;
+    uint64_t disp{0};
+    if ((*dbg.SymGetSymFromAddr64)(proc, entry.__addr_, &disp, sym)) {
+      // Copy chars into the destination string which uses the caller-provided allocator.
+      entry.__desc_ = {sym->Name};
+    } else {
+      Debug() << "SymGetSymFromAddr64 failed: " << GetLastError() << '\n';
+    }
+  }
+}
+
+void win_impl::resolve_lines() {
+  if (!globalInitialized) {
+    return;
+  }
+
+  for (auto& entry : cx_.__entries_) {
+    DWORD disp{0};
+    IMAGEHLP_LINE64 line;
+    line.SizeOfStruct = sizeof(IMAGEHLP_LINE64);
+    if ((*dbg.SymGetLineFromAddr64)(proc, entry.__addr_, &disp, &line)) {
+      // Copy chars into the destination string which uses the caller-provided allocator.
+      entry.__file_ = line.FileName;
+      entry.__line_ = line.LineNumber;
+    } else {
+      Debug() << "SymGetLineFromAddr64 failed: " << GetLastError() << '\n';
+    }
+  }
+}
+
+/*
+Inlining is disabled from here on;
+this is to ensure `collect` below doesn't get merged into its caller
+and mess around with the top of the stack (making `skip` inaccurate).
+*/
+#  pragma auto_inline(off)
+
+_LIBCPP_NO_TAIL_CALLS _LIBCPP_NOINLINE void win_impl::collect(size_t skip, size_t max_depth) {
+  if (!globalInitialized) {
+    return;
+  }
+
+  auto thread  = GetCurrentThread();
+  auto machine = ntHeaders->FileHeader.Machine;
+
+  CONTEXT ccx;
+  RtlCaptureContext(&ccx);
+
+  STACKFRAME64 frame;
+  memset(&frame, 0, sizeof(frame));
+  frame.AddrPC.Mode      = AddrModeFlat;
+  frame.AddrStack.Mode   = AddrModeFlat;
+  frame.AddrFrame.Mode   = AddrModeFlat;
+  frame.AddrPC.Offset    = ccx.Rip;
+  frame.AddrStack.Offset = ccx.Rsp;
+  frame.AddrFrame.Offset = ccx.Rbp;
+
+  while (max_depth &&
+         (*dbg.StackWalk64)(
+             machine,
+             proc,
+             thread,
+             &frame,
+             &ccx,
+             nullptr,
+             dbg.SymFunctionTableAccess64,
+             dbg.SymGetModuleBase64,
+             nullptr)) {
+    if (skip) {
+      --skip;
+      continue;
+    }
+    --max_depth;
+    auto& entry = cx_.__entries_.emplace_back();
+    // We don't need to compute the un-slid addr; windbg only needs the actual addresses.
+    // Assume address is of the instruction after a call instruction, since we can't
+    // differentiate between a signal, SEH exception handler, or a normal function call.
+    entry.__addr_ = frame.AddrPC.Offset - 1; // Back up 1 byte to get into prev insn range
+  }
+}
+
+} // namespace __stacktrace
+_LIBCPP_END_NAMESPACE_STD
+
+#endif // _LIBCPP_STACKTRACE_USE_DBGHELP
diff --git a/libcxx/src/experimental/stacktrace/windows/win_impl.h b/libcxx/src/experimental/stacktrace/windows/win_impl.h
new file mode 100644
index 0000000000000..459347ad9a00f
--- /dev/null
+++ b/libcxx/src/experimental/stacktrace/windows/win_impl.h
@@ -0,0 +1,38 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef _LIBCPP_STACKTRACE_WIN_IMPL_H
+#define _LIBCPP_STACKTRACE_WIN_IMPL_H
+
+#include <__config>
+#include <__config_site>
+#include <cstddef>
+#include <cstdlib>
+#include <mutex>
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+namespace __stacktrace {
+
+struct _LIBCPP_HIDE_FROM_ABI context;
+
+struct win_impl {
+  context& cx_;
+  std::lock_guard<std::mutex> guard_;
+  win_impl(context& trace);
+  ~win_impl();
+
+  void collect(size_t skip, size_t max_depth);
+  void ident_modules();
+  void symbolize();
+  void resolve_lines();
+};
+
+} // namespace __stacktrace
+_LIBCPP_END_NAMESPACE_STD
+
+#endif // _LIBCPP_STACKTRACE_WIN_IMPL_H
diff --git a/libcxx/test/libcxx/stacktrace/simple.o0.nodebug.pass.cpp b/libcxx/test/libcxx/stacktrace/simple.o0.nodebug.pass.cpp
new file mode 100644
index 0000000000000..6c4f3ee6008a2
--- /dev/null
+++ b/libcxx/test/libcxx/stacktrace/simple.o0.nodebug.pass.cpp
@@ -0,0 +1,32 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++03, c++11, c++14, c++17, c++20
+// ADDITIONAL_COMPILE_FLAGS: -O0 -g0
+
+#include <cassert>
+#include <experimental/stacktrace>
+#include <iostream>
+
+int main(int, char**) {
+  // Get the current trace.
+  // uint32_t line_number = __LINE__ + 1; // record where `current` is being called:
+  auto trace = std::stacktrace::current();
+  std::cout << trace << std::endl;
+  // First entry of this should be `main`.
+  auto entry = trace.at(0);
+  assert(entry);
+  assert(entry.native_handle());
+  assert(entry.description() == "main" || entry.description() == "_main");
+  // This is 'nodebug', so we cannot get the source file and line:
+  // assert(entry.source_file().ends_with(".pass.cpp"));
+  // assert(entry.source_line() == line_number);
+  // But this should at least produce the executable filename
+  assert(entry.source_file().contains("simple.o0.nodebug.pass.cpp"));
+  return 0;
+}
diff --git a/libcxx/test/libcxx/stacktrace/simple.o0.nosplit.pass.cpp b/libcxx/test/libcxx/stacktrace/simple.o0.nosplit.pass.cpp
new file mode 100644
index 0000000000000..58d3c8fed5c5e
--- /dev/null
+++ b/libcxx/test/libcxx/stacktrace/simple.o0.nosplit.pass.cpp
@@ -0,0 +1,29 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++03, c++11, c++14, c++17, c++20
+// ADDITIONAL_COMPILE_FLAGS: -O0 -g
+
+#include <cassert>
+#include <experimental/stacktrace>
+#include <iostream>
+
+int main(int, char**) {
+  // Get the current trace.
+  //   uint32_t line_number = __LINE__ + 1; // record where `current` is being called:
+  auto trace = std::stacktrace::current();
+  std::cout << trace << std::endl;
+  // First entry of this should be `main`.
+  auto entry = trace.at(0);
+  assert(entry);
+  assert(entry.native_handle());
+  assert(entry.description() == "main" || entry.description() == "_main");
+  //   assert(entry.source_file().ends_with(".pass.cpp"));
+  //   assert(entry.source_line() == line_number);
+  return 0;
+}
diff --git a/libcxx/test/libcxx/stacktrace/simple.o0.split.pass.cpp b/libcxx/test/libcxx/stacktrace/simple.o0.split.pass.cpp
new file mode 100644
index 0000000000000..a00866181a0e6
--- /dev/null
+++ b/libcxx/test/libcxx/stacktrace/simple.o0.split.pass.cpp
@@ -0,0 +1,29 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++03, c++11, c++14, c++17, c++20
+// ADDITIONAL_COMPILE_FLAGS: -O0 -g -gsplit-dwarf
+
+#include <cassert>
+#include <iostream>
+#include <experimental/stacktrace>
+
+int main(int, char**) {
+  // Get the current trace.
+  //   uint32_t line_number = __LINE__ + 1; // record where `current` is being called:
+  auto trace = std::stacktrace::current();
+  std::cerr << trace << '\n';
+  // First entry of this should be `main`.
+  auto entry = trace.at(0);
+  assert(entry);
+  assert(entry.native_handle());
+  assert(entry.description() == "main" || entry.description() == "_main");
+  //   assert(entry.source_file().ends_with(".pass.cpp"));
+  //   assert(entry.source_line() == line_number);
+  return 0;
+}
diff --git a/libcxx/test/libcxx/stacktrace/simple.o3.nodebug.pass.cpp b/libcxx/test/libcxx/stacktrace/simple.o3.nodebug.pass.cpp
new file mode 100644
index 0000000000000..e8387bfebb14f
--- /dev/null
+++ b/libcxx/test/libcxx/stacktrace/simple.o3.nodebug.pass.cpp
@@ -0,0 +1,32 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++03, c++11, c++14, c++17, c++20
+// ADDITIONAL_COMPILE_FLAGS: -O3 -g0
+
+#include <cassert>
+#include <experimental/stacktrace>
+#include <iostream>
+
+int main(int, char**) {
+  // Get the current trace.
+  // uint32_t line_number = __LINE__ + 1; // record where `current` is being called:
+  auto trace = std::stacktrace::current();
+  std::cout << trace << std::endl;
+  // First entry of this should be `main`.
+  auto entry = trace.at(0);
+  assert(entry);
+  assert(entry.native_handle());
+  assert(entry.description() == "main" || entry.description() == "_main");
+  // This is 'nodebug', so we cannot get the source file and line:
+  // assert(entry.source_file().ends_with(".pass.cpp"));
+  // assert(entry.source_line() == line_number);
+  // But this should at least produce the executable filename
+  assert(entry.source_file().contains("simple.o3.nodebug.pass.cpp"));
+  return 0;
+}
diff --git a/libcxx/test/libcxx/stacktrace/simple.o3.nosplit.pass.cpp b/libcxx/test/libcxx/stacktrace/simple.o3.nosplit.pass.cpp
new file mode 100644
index 0000000000000..e3796c2bc8add
--- /dev/null
+++ b/libcxx/test/libcxx/stacktrace/simple.o3.nosplit.pass.cpp
@@ -0,0 +1,29 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++03, c++11, c++14, c++17, c++20
+// ADDITIONAL_COMPILE_FLAGS: -O3 -g
+
+#include <cassert>
+#include <experimental/stacktrace>
+#include <iostream>
+
+int main(int, char**) {
+  // Get the current trace.
+  //   uint32_t line_number = __LINE__ + 1; // record where `current` is being called:
+  auto trace = std::stacktrace::current();
+  std::cout << trace << std::endl;
+  // First entry of this should be `main`.
+  auto entry = trace.at(0);
+  assert(entry);
+  assert(entry.native_handle());
+  assert(entry.description() == "main" || entry.description() == "_main");
+  //   assert(entry.source_file().ends_with(".pass.cpp"));
+  //   assert(entry.source_line() == line_number);
+  return 0;
+}
diff --git a/libcxx/test/libcxx/stacktrace/simple.o3.split.pass.cpp b/libcxx/test/libcxx/stacktrace/simple.o3.split.pass.cpp
new file mode 100644
index 0000000000000..7b58f9accf7c9
--- /dev/null
+++ b/libcxx/test/libcxx/stacktrace/simple.o3.split.pass.cpp
@@ -0,0 +1,29 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++03, c++11, c++14, c++17, c++20
+// ADDITIONAL_COMPILE_FLAGS: -O3 -g -gsplit-dwarf
+
+#include <cassert>
+#include <experimental/stacktrace>
+#include <iostream>
+
+int main(int, char**) {
+  // Get the current trace.
+  //   uint32_t line_number = __LINE__ + 1; // record where `current` is being called:
+  auto trace = std::stacktrace::current();
+  std::cout << trace << std::endl;
+  // First entry of this should be `main`.
+  auto entry = trace.at(0);
+  assert(entry);
+  assert(entry.native_handle());
+  assert(entry.description() == "main" || entry.description() == "_main");
+  //   assert(entry.source_file().ends_with(".pass.cpp"));
+  //   assert(entry.source_line() == line_number);
+  return 0;
+}
diff --git a/libcxx/test/libcxx/transitive_includes/cxx03.csv b/libcxx/test/libcxx/transitive_includes/cxx03.csv
index c0031543e47bc..920a6145a02b8 100644
--- a/libcxx/test/libcxx/transitive_includes/cxx03.csv
+++ b/libcxx/test/libcxx/transitive_includes/cxx03.csv
@@ -122,15 +122,19 @@ atomic ratio
 atomic type_traits
 atomic version
 barrier atomic
+barrier cctype
 barrier climits
 barrier cmath
 barrier compare
 barrier concepts
 barrier cstddef
 barrier cstdint
+barrier cstdio
 barrier cstdlib
 barrier cstring
 barrier ctime
+barrier cwchar
+barrier cwctype
 barrier exception
 barrier initializer_list
 barrier iosfwd
@@ -2032,6 +2036,7 @@ stdexcept new
 stdexcept type_traits
 stdexcept typeinfo
 stdexcept version
+stop_token cstddef
 stop_token iosfwd
 stop_token version
 streambuf algorithm
diff --git a/libcxx/test/libcxx/transitive_includes/cxx11.csv b/libcxx/test/libcxx/transitive_includes/cxx11.csv
index c0031543e47bc..920a6145a02b8 100644
--- a/libcxx/test/libcxx/transitive_includes/cxx11.csv
+++ b/libcxx/test/libcxx/transitive_includes/cxx11.csv
@@ -122,15 +122,19 @@ atomic ratio
 atomic type_traits
 atomic version
 barrier atomic
+barrier cctype
 barrier climits
 barrier cmath
 barrier compare
 barrier concepts
 barrier cstddef
 barrier cstdint
+barrier cstdio
 barrier cstdlib
 barrier cstring
 barrier ctime
+barrier cwchar
+barrier cwctype
 barrier exception
 barrier initializer_list
 barrier iosfwd
@@ -2032,6 +2036,7 @@ stdexcept new
 stdexcept type_traits
 stdexcept typeinfo
 stdexcept version
+stop_token cstddef
 stop_token iosfwd
 stop_token version
 streambuf algorithm
diff --git a/libcxx/test/libcxx/transitive_includes/cxx14.csv b/libcxx/test/libcxx/transitive_includes/cxx14.csv
index c2eb5b44e8d7a..cfcf7bc7c4c19 100644
--- a/libcxx/test/libcxx/transitive_includes/cxx14.csv
+++ b/libcxx/test/libcxx/transitive_includes/cxx14.csv
@@ -125,15 +125,19 @@ atomic ratio
 atomic type_traits
 atomic version
 barrier atomic
+barrier cctype
 barrier climits
 barrier cmath
 barrier compare
 barrier concepts
 barrier cstddef
 barrier cstdint
+barrier cstdio
 barrier cstdlib
 barrier cstring
 barrier ctime
+barrier cwchar
+barrier cwctype
 barrier exception
 barrier initializer_list
 barrier iosfwd
@@ -2072,6 +2076,7 @@ stdexcept new
 stdexcept type_traits
 stdexcept typeinfo
 stdexcept version
+stop_token cstddef
 stop_token iosfwd
 stop_token version
 streambuf algorithm
diff --git a/libcxx/test/libcxx/transitive_includes/cxx17.csv b/libcxx/test/libcxx/transitive_includes/cxx17.csv
index 332cb62f35b5f..534776e6f0526 100644
--- a/libcxx/test/libcxx/transitive_includes/cxx17.csv
+++ b/libcxx/test/libcxx/transitive_includes/cxx17.csv
@@ -122,15 +122,19 @@ atomic ratio
 atomic type_traits
 atomic version
 barrier atomic
+barrier cctype
 barrier climits
 barrier cmath
 barrier compare
 barrier concepts
 barrier cstddef
 barrier cstdint
+barrier cstdio
 barrier cstdlib
 barrier cstring
 barrier ctime
+barrier cwchar
+barrier cwctype
 barrier exception
 barrier initializer_list
 barrier iosfwd
@@ -2085,6 +2089,7 @@ stdexcept new
 stdexcept type_traits
 stdexcept typeinfo
 stdexcept version
+stop_token cstddef
 stop_token iosfwd
 stop_token version
 streambuf algorithm
diff --git a/libcxx/test/libcxx/transitive_includes/cxx23.csv b/libcxx/test/libcxx/transitive_includes/cxx23.csv
index cb23c7a98de1b..fbfa8152b8070 100644
--- a/libcxx/test/libcxx/transitive_includes/cxx23.csv
+++ b/libcxx/test/libcxx/transitive_includes/cxx23.csv
@@ -295,6 +295,35 @@ experimental/propagate_const version
 experimental/simd cstdint
 experimental/simd limits
 experimental/simd version
+experimental/stacktrace bitset
+experimental/stacktrace cctype
+experimental/stacktrace cerrno
+experimental/stacktrace climits
+experimental/stacktrace clocale
+experimental/stacktrace compare
+experimental/stacktrace cstddef
+experimental/stacktrace cstdint
+experimental/stacktrace cstdio
+experimental/stacktrace cstdlib
+experimental/stacktrace cstring
+experimental/stacktrace ctime
+experimental/stacktrace cwchar
+experimental/stacktrace cwctype
+experimental/stacktrace initializer_list
+experimental/stacktrace ios
+experimental/stacktrace iosfwd
+experimental/stacktrace limits
+experimental/stacktrace list
+experimental/stacktrace locale
+experimental/stacktrace memory
+experimental/stacktrace ratio
+experimental/stacktrace stdexcept
+experimental/stacktrace streambuf
+experimental/stacktrace string
+experimental/stacktrace string_view
+experimental/stacktrace tuple
+experimental/stacktrace typeinfo
+experimental/stacktrace version
 experimental/type_traits cstdint
 experimental/type_traits initializer_list
 experimental/type_traits type_traits
diff --git a/libcxx/test/libcxx/transitive_includes/cxx26.csv b/libcxx/test/libcxx/transitive_includes/cxx26.csv
index ce8f0261f2b27..06dd30b07537e 100644
--- a/libcxx/test/libcxx/transitive_includes/cxx26.csv
+++ b/libcxx/test/libcxx/transitive_includes/cxx26.csv
@@ -295,6 +295,35 @@ experimental/propagate_const version
 experimental/simd cstdint
 experimental/simd limits
 experimental/simd version
+experimental/stacktrace bitset
+experimental/stacktrace cctype
+experimental/stacktrace cerrno
+experimental/stacktrace climits
+experimental/stacktrace clocale
+experimental/stacktrace compare
+experimental/stacktrace cstddef
+experimental/stacktrace cstdint
+experimental/stacktrace cstdio
+experimental/stacktrace cstdlib
+experimental/stacktrace cstring
+experimental/stacktrace ctime
+experimental/stacktrace cwchar
+experimental/stacktrace cwctype
+experimental/stacktrace initializer_list
+experimental/stacktrace ios
+experimental/stacktrace iosfwd
+experimental/stacktrace limits
+experimental/stacktrace list
+experimental/stacktrace locale
+experimental/stacktrace memory
+experimental/stacktrace ratio
+experimental/stacktrace stdexcept
+experimental/stacktrace streambuf
+experimental/stacktrace string
+experimental/stacktrace string_view
+experimental/stacktrace tuple
+experimental/stacktrace typeinfo
+experimental/stacktrace version
 experimental/type_traits cstdint
 experimental/type_traits initializer_list
 experimental/type_traits type_traits
diff --git a/libcxx/test/std/diagnostics/stacktrace/basic.cmp.pass.cpp b/libcxx/test/std/diagnostics/stacktrace/basic.cmp.pass.cpp
new file mode 100644
index 0000000000000..495abe79da20f
--- /dev/null
+++ b/libcxx/test/std/diagnostics/stacktrace/basic.cmp.pass.cpp
@@ -0,0 +1,106 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++03, c++11, c++14, c++17, c++20
+
+#include <experimental/stacktrace>
+
+#include <cassert>
+
+/*
+  (19.6.4.4) Comparisons [stacktrace.basic.cmp]
+
+  template<class Allocator2>
+  friend bool operator==(const basic_stacktrace& x,
+                          const basic_stacktrace<Allocator2>& y) noexcept;
+
+  template<class Allocator2>
+  friend strong_ordering operator<=>(const basic_stacktrace& x,
+                                      const basic_stacktrace<Allocator2>& y) noexcept;
+*/
+
+_LIBCPP_NO_TAIL_CALLS _LIBCPP_NOINLINE std::stacktrace test1() { return std::stacktrace::current(); }
+
+_LIBCPP_NO_TAIL_CALLS _LIBCPP_NOINLINE std::stacktrace test2a() { return test1(); }
+
+_LIBCPP_NO_TAIL_CALLS _LIBCPP_NOINLINE std::stacktrace test2b() { return test1(); }
+
+_LIBCPP_NO_TAIL_CALLS
+int main(int, char**) {
+  /*    
+    template<class Allocator2>
+    friend bool operator==(const basic_stacktrace& x, const basic_stacktrace<Allocator2>& y) noexcept;
+    Returns: equal(x.begin(), x.end(), y.begin(), y.end()).
+  */
+  auto st1a = test1(); // [test1, main, ...]
+  assert(st1a == st1a);
+
+  auto st1b = st1a;
+  assert(st1a == st1b);
+
+  auto st2a = test2a(); // [test1, test2a, main, ...]
+  assert(st1a != st2a);
+
+  std::stacktrace empty; // []
+  assert(st1a != empty);
+  assert(st2a != empty);
+
+  assert(st2a.size() > st1a.size());
+  assert(st1a.size() > empty.size());
+
+  auto st2b = test2b(); // [test1, test2b, main, ...]
+  assert(st2a.size() == st2b.size());
+  assert(st2a != st2b);
+
+  /*    
+    template<class Allocator2>
+    friend strong_ordering
+    operator<=>(const basic_stacktrace& x, const basic_stacktrace<Allocator2>& y) noexcept;
+
+    Returns: x.size() <=> y.size() if x.size() != y.size();
+    lexicographical_compare_three_way(x.begin(), x.end(), y.begin(), y.end()) otherwise.
+  */
+
+  // empty:  []
+  // st1a:   [test1, main, ...]
+  // st1b:   [test1, main, ...] (copy of st1a)
+  // st2a:   [test1, test2a, main:X, ...]
+  // st2b:   [test1, test2b, main:Y, ...], Y > X
+
+  assert(std::strong_ordering::equal == empty <=> empty);
+  assert(std::strong_ordering::less == empty <=> st1a);
+  assert(std::strong_ordering::less == empty <=> st1b);
+  assert(std::strong_ordering::less == empty <=> st2a);
+  assert(std::strong_ordering::less == empty <=> st2b);
+
+  assert(std::strong_ordering::greater == st1a <=> empty);
+  assert(std::strong_ordering::equal == st1a <=> st1a);
+  assert(std::strong_ordering::equal == st1a <=> st1b);
+  assert(std::strong_ordering::less == st1a <=> st2a);
+  assert(std::strong_ordering::less == st1a <=> st2b);
+
+  assert(std::strong_ordering::greater == st1b <=> empty);
+  assert(std::strong_ordering::equal == st1b <=> st1a);
+  assert(std::strong_ordering::equal == st1b <=> st1b);
+  assert(std::strong_ordering::less == st1b <=> st2a);
+  assert(std::strong_ordering::less == st1b <=> st2b);
+
+  assert(std::strong_ordering::greater == st2a <=> empty);
+  assert(std::strong_ordering::greater == st2a <=> st1a);
+  assert(std::strong_ordering::greater == st2a <=> st1b);
+  assert(std::strong_ordering::equal == st2a <=> st2a);
+  assert(std::strong_ordering::less == st2a <=> st2b);
+
+  assert(std::strong_ordering::greater == st2b <=> empty);
+  assert(std::strong_ordering::greater == st2b <=> st1a);
+  assert(std::strong_ordering::greater == st2b <=> st1b);
+  assert(std::strong_ordering::greater == st2b <=> st2a);
+  assert(std::strong_ordering::equal == st2b <=> st2b);
+
+  return 0;
+}
diff --git a/libcxx/test/std/diagnostics/stacktrace/basic.cons.pass.cpp b/libcxx/test/std/diagnostics/stacktrace/basic.cons.pass.cpp
new file mode 100644
index 0000000000000..64e54fdf5793d
--- /dev/null
+++ b/libcxx/test/std/diagnostics/stacktrace/basic.cons.pass.cpp
@@ -0,0 +1,308 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++03, c++11, c++14, c++17, c++20
+// ADDITIONAL_COMPILE_FLAGS: -O1 -g
+
+#include <experimental/stacktrace>
+
+#include <cassert>
+#include <iostream>
+
+/**
+ * This file includes tests which ensure any allocations performed by `basic_stacktrace`
+ * are done via the user-provided allocator, and not via bare `malloc` / `operator new`s.
+ * Our overridden `malloc` below will fail if `malloc_disabled` is `true`.
+ * The program's startup code may need to malloc, so we'll allow malloc initially.
+ * This is only activated during the "test_no_malloc_or_new_ex_allocator" test,
+ * during which it should be using a `test_alloc` we'll provide (which knows how to
+ * unblock `malloc` temporarily).
+ */
+bool malloc_disabled{false};
+
+void* malloc(size_t size) {
+  // If flag has not been temporarily disabled by our allocator, abort
+  if (malloc_disabled) {
+    abort();
+  }
+  // Since we overrode malloc with this function, and there's no way to call up
+  // to the "real malloc", allocate a different way.  Assumes nothing actually uses `calloc`.
+  return calloc(1, size);
+}
+
+// All the various ways to monkey around with heap memory without an allocator:
+// we'll simply redirect these through our gate-keeping `malloc` above.
+void* operator new(size_t size) { return malloc(size); }
+void* operator new[](size_t size) { return malloc(size); }
+void operator delete(void* ptr) noexcept { free(ptr); }
+void operator delete(void* ptr, size_t) noexcept { free(ptr); }
+void operator delete[](void* ptr) noexcept { free(ptr); }
+void operator delete[](void* ptr, size_t) noexcept { free(ptr); }
+
+/** RAII-style scope object to temporarily permit heap allocations, used by `test_alloc`.*/
+struct scope_enable_malloc {
+  bool prev_malloc_disabled_;
+  scope_enable_malloc() : prev_malloc_disabled_(malloc_disabled) { malloc_disabled = false; }
+  ~scope_enable_malloc() { malloc_disabled = true; }
+};
+
+template <typename T>
+struct test_alloc {
+  using size_type     = size_t;
+  using value_type    = T;
+  using pointer       = T*;
+  using const_pointer = T const*;
+
+  template <typename U>
+  struct rebind {
+    using other = test_alloc<U>;
+  };
+
+  std::allocator<T> wrapped_{};
+
+  test_alloc() = default;
+
+  template <typename U>
+  test_alloc(test_alloc<U> const& rhs) : wrapped_(rhs.wrapped_) {}
+
+  bool operator==(auto const& rhs) const { return &rhs == this; }
+  bool operator==(test_alloc const&) const { return true; }
+
+  T* allocate(size_t n) { return wrapped_.allocate(n); }
+
+  auto allocate_at_least(size_t n) { return wrapped_.allocate_at_least(n); }
+
+  void deallocate(T* ptr, size_t n) { return wrapped_.deallocate(ptr, n); }
+};
+
+/*
+  (19.6.4.2)
+
+  // [stacktrace.basic.cons], creation and assignment
+  static basic_stacktrace current(const allocator_type& alloc = allocator_type()) noexcept;   [1]
+  static basic_stacktrace current(size_type skip,
+                                  const allocator_type& alloc = allocator_type()) noexcept;   [2]
+  static basic_stacktrace current(size_type skip, size_type max_depth,
+                                  const allocator_type& alloc = allocator_type()) noexcept;   [3]
+
+  basic_stacktrace() noexcept(is_nothrow_default_constructible_v<allocator_type>);            [4]
+  explicit basic_stacktrace(const allocator_type& alloc) noexcept;                            [5]
+
+  basic_stacktrace(const basic_stacktrace& other);                                            [6]
+  basic_stacktrace(basic_stacktrace&& other) noexcept;                                        [7]
+  basic_stacktrace(const basic_stacktrace& other, const allocator_type& alloc);               [8]
+  basic_stacktrace(basic_stacktrace&& other, const allocator_type& alloc);                    [9]
+  basic_stacktrace& operator=(const basic_stacktrace& other);                                 [10]
+  basic_stacktrace& operator=(basic_stacktrace&& other)
+    noexcept(allocator_traits<Allocator>::propagate_on_container_move_assignment::value ||
+      allocator_traits<Allocator>::is_always_equal::value);                                   [11]
+
+  ~basic_stacktrace();                                                                        [12]
+*/
+
+// clang-format off
+uint32_t test1_line;
+uint32_t test2_line;
+
+template <class A>
+_LIBCPP_NO_TAIL_CALLS _LIBCPP_NOINLINE
+std::basic_stacktrace<A> test1(A& alloc) {
+  test1_line = __LINE__ + 1; // add 1 to get the next line (where the call to `current` occurs)
+  auto ret = std::basic_stacktrace<A>::current(alloc);
+  return ret;
+}
+
+template <class A>
+_LIBCPP_NO_TAIL_CALLS _LIBCPP_NOINLINE
+std::basic_stacktrace<A> test2(A& alloc) {
+  test2_line = __LINE__ + 1; // add 1 to get the next line (where the call to `current` occurs)
+  auto ret = test1(alloc);
+  return ret;
+}
+// clang-format on
+
+/*
+    [1]
+    static basic_stacktrace current(const allocator_type& alloc = allocator_type()) noexcept;
+
+    Returns: A basic_stacktrace object with frames_ storing the stacktrace of the current evaluation
+    in the current thread of execution, or an empty basic_stacktrace object if the initialization of
+    frames_ failed. alloc is passed to the constructor of the frames_ object.
+    [Note 1: If the stacktrace was successfully obtained, then frames_.front() is the stacktrace_entry
+    representing approximately the current evaluation, and frames_.back() is the stacktrace_entry
+    representing approximately the initial function of the current thread of execution. — end note]
+  */
+_LIBCPP_NO_TAIL_CALLS _LIBCPP_NOINLINE void test_current() {
+  test_alloc<std::stacktrace_entry> alloc;
+  uint32_t main_line = __LINE__ + 1;
+  auto st            = test2(alloc);
+
+  std::cerr << "*** Stacktrace obtained at line " << main_line << '\n' << st << '\n';
+
+  assert(st.size() >= 3);
+  assert(st[0]);
+  assert(st[0].native_handle());
+  assert(st[0].description().contains("test1"));
+  assert(st[0].source_file().contains("basic.cons.pass.cpp"));
+  assert(st[1]);
+  assert(st[1].native_handle());
+  assert(st[1].description().contains("test2"));
+  assert(st[1].source_file().contains("basic.cons.pass.cpp"));
+  assert(st[2]);
+  assert(st[2].native_handle());
+  assert(st[2].description().contains("test_current"));
+  assert(st[2].source_file().contains("basic.cons.pass.cpp"));
+
+  // We unfortunately cannot guarantee the following; in CI, and possibly on users' build machines,
+  // there may not be an up-to-date version of e.g. `addr2line`.
+  // assert(st[0].source_file().ends_with("basic.cons.pass.cpp"));
+  // assert(st[0].source_line() == test1_line);
+  // assert(st[1].source_file().ends_with("basic.cons.pass.cpp"));
+  // assert(st[1].source_line() == test2_line);
+  // assert(st[2].source_file().ends_with("basic.cons.pass.cpp"));
+  // assert(st[2].source_line() == main_line);
+}
+
+/*
+  [2]
+  static basic_stacktrace current(size_type skip,
+                              const allocator_type& alloc = allocator_type()) noexcept;
+  Let t be a stacktrace as-if obtained via basic_stacktrace​::​current(alloc). Let n be t.size().
+  Returns: A basic_stacktrace object where frames_ is direct-non-list-initialized from arguments
+  t.begin() + min(n, skip), t.end(), and alloc, or an empty basic_stacktrace object if the
+  initialization of frames_ failed.
+*/
+_LIBCPP_NO_TAIL_CALLS _LIBCPP_NOINLINE void test_current_with_skip() {
+  // Use default allocator for simplicity; alloc is covered above
+  auto st_skip0 = std::stacktrace::current();
+  std::cerr << "*** st_skip0:\n" << st_skip0 << '\n';
+  assert(st_skip0.size() >= 2);
+  auto st_skip1 = std::stacktrace::current(1);
+  std::cerr << "*** st_skip1:\n" << st_skip1 << '\n';
+  assert(st_skip1.size() >= 1);
+  assert(st_skip0.size() == st_skip1.size() + 1);
+  assert(st_skip0[1] == st_skip1[0]);
+  auto st_skip_many = std::stacktrace::current(1 << 20);
+  assert(st_skip_many.empty());
+}
+
+/*
+  [3]
+  static basic_stacktrace current(size_type skip, size_type max_depth,
+                              const allocator_type& alloc = allocator_type()) noexcept;
+  Let t be a stacktrace as-if obtained via basic_stacktrace​::​current(alloc). Let n be t.size().
+  Preconditions: skip <= skip + max_depth is true.
+  Returns: A basic_stacktrace object where frames_ is direct-non-list-initialized from arguments
+  t.begin() + min(n, skip), t.begin() + min(n, skip + max_depth), and alloc, or an empty
+  basic_stacktrace object if the initialization of frames_ failed.
+*/
+_LIBCPP_NO_TAIL_CALLS _LIBCPP_NOINLINE void test_current_with_skip_depth() {
+  // current stack is: [this function, main, (possibly something else, e.g. `_start` from libc)]
+  // so it's probably 3 functions deep -- but certainly at least 2 deep.
+  auto st = std::stacktrace::current();
+  assert(st.size() >= 2);
+  auto it     = st.begin();
+  auto entry1 = *(it++); // represents this function
+  auto entry2 = *(it++); // represents our caller, `main`
+
+  // get current trace again, but skip the 1st
+  st = std::stacktrace::current(1, 1);
+  assert(st.size() >= 1);
+  assert(*st.begin() == entry2);
+}
+
+/*
+  [4]
+  basic_stacktrace() noexcept(is_nothrow_default_constructible_v<allocator_type>);
+  Postconditions: empty() is true.
+*/
+_LIBCPP_NO_TAIL_CALLS _LIBCPP_NOINLINE void test_default_construct() {
+  std::stacktrace st;
+  assert(st.empty());
+}
+
+/*
+  [5]
+  explicit basic_stacktrace(const allocator_type& alloc) noexcept;
+  Effects: alloc is passed to the frames_ constructor.
+  Postconditions: empty() is true.
+*/
+_LIBCPP_NO_TAIL_CALLS _LIBCPP_NOINLINE void test_construct_with_allocator() {
+  test_alloc<std::stacktrace_entry> alloc;
+  std::basic_stacktrace<decltype(alloc)> st(alloc);
+  assert(st.empty());
+
+  st = std::basic_stacktrace<decltype(alloc)>::current(alloc);
+  assert(!st.empty());
+}
+
+/*
+  [6] basic_stacktrace(const basic_stacktrace& other);
+  [7] basic_stacktrace(basic_stacktrace&& other) noexcept;
+  [8] basic_stacktrace(const basic_stacktrace& other, const allocator_type& alloc);
+  [9] basic_stacktrace(basic_stacktrace&& other, const allocator_type& alloc);
+  [10] basic_stacktrace& operator=(const basic_stacktrace& other);
+  [11] basic_stacktrace& operator=(basic_stacktrace&& other)
+    noexcept(allocator_traits<Allocator>::propagate_on_container_move_assignment::value ||
+    allocator_traits<Allocator>::is_always_equal::value);
+  
+  Remarks: Implementations may strengthen the exception specification for these functions
+  ([res.on.exception.handling]) by ensuring that empty() is true on failed allocation.
+*/
+_LIBCPP_NO_TAIL_CALLS _LIBCPP_NOINLINE void test_copy_move_ctors() {
+  using A = std::allocator<std::stacktrace_entry>;
+  A alloc;
+  auto st = std::basic_stacktrace<A>::current(alloc);
+
+  auto copy_constr = std::basic_stacktrace<A>(st);
+  assert(st == copy_constr);
+
+  std::basic_stacktrace<A> copy_assign;
+  copy_assign = std::basic_stacktrace<A>(st);
+  assert(st == copy_assign);
+
+  auto st2 = test2(alloc);
+  assert(st2.size());
+  std::basic_stacktrace<A> move_constr(std::move(st2));
+  assert(move_constr.size());
+  assert(!st2.size());
+
+  auto st3 = test2(alloc);
+  assert(st3.size());
+  std::basic_stacktrace<A> move_assign;
+  move_assign = std::move(st3);
+  assert(move_assign.size());
+  assert(!st3.size());
+
+  // TODO(stacktrace23): should we add test cases with `select_on_container_copy_construction`?
+}
+
+/** Ensure all allocations take place through a given allocator, and that none
+ * are sneaking around it by accidentally using malloc or operator new. */
+void test_no_malloc_or_new_ex_allocator() {
+  // A generic allocator we'll use for everything
+  using A = test_alloc<std::stacktrace_entry>;
+  A alloc;
+  // After this point all stacktrace operations must properly use `alloc`
+  malloc_disabled = true;
+  // Try all the stack trace operations
+  auto st = std::basic_stacktrace<A>(alloc);
+}
+
+_LIBCPP_NO_TAIL_CALLS
+int main(int, char**) {
+  test_current();
+  test_current_with_skip();
+  test_current_with_skip_depth();
+  test_default_construct();
+  test_construct_with_allocator();
+  test_copy_move_ctors();
+  test_no_malloc_or_new_ex_allocator();
+
+  return 0;
+}
diff --git a/libcxx/test/std/diagnostics/stacktrace/basic.hash.pass.cpp b/libcxx/test/std/diagnostics/stacktrace/basic.hash.pass.cpp
new file mode 100644
index 0000000000000..db33a8fabb41a
--- /dev/null
+++ b/libcxx/test/std/diagnostics/stacktrace/basic.hash.pass.cpp
@@ -0,0 +1,44 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++03, c++11, c++14, c++17, c++20
+
+#include <experimental/stacktrace>
+
+#include <cassert>
+
+/*
+  (19.6.6) Hash Support
+
+  template<> struct hash<stacktrace_entry>;                                 [1]
+  template<class Allocator> struct hash<basic_stacktrace<Allocator>>;       [2]
+
+  The specializations are enabled ([unord.hash]).
+*/
+
+int main(int, char**) {
+  /*
+  [1]
+  template<> struct hash<stacktrace_entry>;
+  */
+  std::stacktrace_entry empty_entry;
+  assert(std::hash<std::stacktrace_entry>()(empty_entry) == 0);
+
+  /*
+  [2]
+  template<class Allocator> struct hash<basic_stacktrace<Allocator>>;
+  */
+  std::stacktrace trace; // initially empty
+  auto hash_val_empty    = std::hash<std::stacktrace>()(trace);
+  trace                  = /* reassign */ std::stacktrace::current();
+  auto hash_val_nonempty = std::hash<std::stacktrace>()(trace);
+
+  assert(hash_val_empty != hash_val_nonempty);
+
+  return 0;
+}
diff --git a/libcxx/test/std/diagnostics/stacktrace/basic.mod.pass.cpp b/libcxx/test/std/diagnostics/stacktrace/basic.mod.pass.cpp
new file mode 100644
index 0000000000000..5929cd8f8d0f9
--- /dev/null
+++ b/libcxx/test/std/diagnostics/stacktrace/basic.mod.pass.cpp
@@ -0,0 +1,40 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++03, c++11, c++14, c++17, c++20
+
+#include <experimental/stacktrace>
+
+#include <cassert>
+
+/*
+  (19.6.4.5) Modifiers [stacktrace.basic.mod]
+
+  void swap(basic_stacktrace& other)
+      noexcept(allocator_traits<Allocator>::propagate_on_container_swap::value ||
+      allocator_traits<Allocator>::is_always_equal::value);
+
+  Effects: Exchanges the contents of *this and other.
+*/
+int main(int, char**) {
+  std::stacktrace empty;
+  auto current = std::stacktrace::current();
+
+  std::stacktrace a(empty);
+  std::stacktrace b(current);
+  assert(a == empty);
+  assert(b == current);
+
+  a.swap(b);
+  assert(a == current);
+  assert(b == empty);
+
+  // TODO(stacktrace23): should we also test swap w/ `select_on_container_swap` case
+
+  return 0;
+}
diff --git a/libcxx/test/std/diagnostics/stacktrace/basic.nonmem.pass.cpp b/libcxx/test/std/diagnostics/stacktrace/basic.nonmem.pass.cpp
new file mode 100644
index 0000000000000..665fb475f56e9
--- /dev/null
+++ b/libcxx/test/std/diagnostics/stacktrace/basic.nonmem.pass.cpp
@@ -0,0 +1,91 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++03, c++11, c++14, c++17, c++20
+
+#include <experimental/stacktrace>
+
+#include <cassert>
+#include <sstream>
+
+/*
+  (19.6.4.6) Non-member functions
+
+  template<class Allocator>
+    void swap(basic_stacktrace<Allocator>& a, basic_stacktrace<Allocator>& b)
+      noexcept(noexcept(a.swap(b)));
+
+  string to_string(const stacktrace_entry& f);
+
+  template<class Allocator>
+    string to_string(const basic_stacktrace<Allocator>& st);
+
+  ostream& operator<<(ostream& os, const stacktrace_entry& f);
+  template<class Allocator>
+    ostream& operator<<(ostream& os, const basic_stacktrace<Allocator>& st);
+*/
+int main(int, char**) {
+  /*
+  template<class Allocator>
+  void swap(basic_stacktrace<Allocator>& a, basic_stacktrace<Allocator>& b)
+    noexcept(noexcept(a.swap(b)));
+  Effects: Equivalent to a.swap(b).
+  */
+  std::stacktrace empty;
+  auto current = std::stacktrace::current();
+
+  std::stacktrace a(empty);
+  std::stacktrace b(current);
+  assert(a == empty);
+  assert(b == current);
+
+  std::swap(a, b);
+  assert(a == current);
+  assert(b == empty);
+
+  /*
+  string to_string(const stacktrace_entry& f);
+  Returns: A string with a description of f.
+  Recommended practice: The description should provide information about the contained evaluation,
+  including information from f.source_file() and f.source_line().
+  */
+
+  assert(std::to_string(a[0]).contains("main"));
+  assert(std::to_string(a[0]).contains("basic.nonmem.pass"));
+
+  /*
+  template<class Allocator>
+  string to_string(const basic_stacktrace<Allocator>& st);
+  Returns: A string with a description of st.
+  [Note 1: The number of lines is not guaranteed to be equal to st.size(). — end note]
+  */
+
+  assert(std::to_string(a).contains("main"));
+  assert(std::to_string(a).contains("basic.nonmem.pass"));
+
+  /*
+  ostream& operator<<(ostream& os, const stacktrace_entry& f);
+  Effects: Equivalent to: return os << to_string(f);
+  */
+
+  std::stringstream entry_os;
+  entry_os << a[0];
+  assert(entry_os.str() == std::to_string(a[0]));
+
+  /*
+  template<class Allocator>
+    ostream& operator<<(ostream& os, const basic_stacktrace<Allocator>& st);
+  Effects: Equivalent to: return os << to_string(st);
+  */
+
+  std::stringstream trace_os;
+  trace_os << a;
+  assert(trace_os.str() == std::to_string(a));
+
+  return 0;
+}
diff --git a/libcxx/test/std/diagnostics/stacktrace/basic.obs.pass.cpp b/libcxx/test/std/diagnostics/stacktrace/basic.obs.pass.cpp
new file mode 100644
index 0000000000000..b5c6cf77dde71
--- /dev/null
+++ b/libcxx/test/std/diagnostics/stacktrace/basic.obs.pass.cpp
@@ -0,0 +1,156 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++03, c++11, c++14, c++17, c++20
+
+#include <experimental/stacktrace>
+#include <iostream>
+#include <iterator>
+#include <memory>
+
+#include <cassert>
+#include <stdexcept>
+
+/*
+  (19.6.4.3) Observers [stacktrace.basic.obs]
+
+  // [stacktrace.basic.obs], observers
+  allocator_type get_allocator() const noexcept;      [1]
+
+  const_iterator begin() const noexcept;              [2]
+  const_iterator end() const noexcept;                [3]
+  const_reverse_iterator rbegin() const noexcept;     [4]
+  const_reverse_iterator rend() const noexcept;       [5]
+
+  const_iterator cbegin() const noexcept;             [6]
+  const_iterator cend() const noexcept;               [7]
+  const_reverse_iterator crbegin() const noexcept;    [8]
+  const_reverse_iterator crend() const noexcept;      [9]
+
+  bool empty() const noexcept;                        [10]
+  size_type size() const noexcept;                    [11]
+  size_type max_size() const noexcept;                [12]
+
+  const_reference operator[](size_type) const;        [13]
+  const_reference at(size_type) const;                [14]
+*/
+
+_LIBCPP_NO_TAIL_CALLS _LIBCPP_NOINLINE std::stacktrace test1() { return std::stacktrace::current(0, 4); }
+_LIBCPP_NO_TAIL_CALLS _LIBCPP_NOINLINE std::stacktrace test2() { return test1(); }
+_LIBCPP_NO_TAIL_CALLS _LIBCPP_NOINLINE std::stacktrace test3() { return test2(); }
+
+_LIBCPP_NO_TAIL_CALLS
+int main(int, char**) {
+  std::stacktrace st;
+
+  /*
+    using const_iterator = implementation-defined;
+    The type models random_access_iterator ([iterator.concept.random.access]) and meets the
+    Cpp17RandomAccessIterator requirements ([random.access.iterators]).
+  */
+  static_assert(std::random_access_iterator<decltype(st.begin())>);
+  static_assert(std::random_access_iterator<decltype(st.rbegin())>);
+  static_assert(std::random_access_iterator<decltype(st.cbegin())>);
+  static_assert(std::random_access_iterator<decltype(st.crbegin())>);
+
+  /*
+    allocator_type get_allocator() const noexcept;
+    Returns: frames_.get_allocator().
+  */
+  static_assert(std::same_as<decltype(st.get_allocator()), std::stacktrace::allocator_type>);
+
+  /*
+    const_iterator begin() const noexcept;
+    const_iterator cbegin() const noexcept;
+    Returns: An iterator referring to the first element in frames_. If empty() is true,
+    then it returns the same value as end().
+
+    const_iterator end() const noexcept;
+    const_iterator cend() const noexcept;
+    Returns: The end iterator.
+
+    const_reverse_iterator rbegin() const noexcept;
+    const_reverse_iterator crbegin() const noexcept;
+    Returns: reverse_iterator(cend()).
+
+    const_reverse_iterator rend() const noexcept;
+    const_reverse_iterator crend() const noexcept;
+    Returns: reverse_iterator(cbegin()).
+  */
+
+  // st is initially empty:
+  assert(st.begin() == st.end());
+  assert(st.cbegin() == st.cend());
+  assert(st.rbegin() == st.rend());
+  assert(st.crbegin() == st.crend());
+
+  /*
+    bool empty() const noexcept;
+    Returns: frames_.empty().
+  */
+  assert(st.empty());
+  assert(st.size() == 0);
+
+  // no longer empty:
+  st = test3();
+  assert(!st.empty());
+  assert(st.begin() != st.end());
+  assert(st.cbegin() != st.cend());
+
+  /*
+    size_type size() const noexcept;
+    Returns: frames_.size().
+
+    size_type max_size() const noexcept;
+    Returns: frames_.max_size().
+  */
+  std::cout << st << std::endl;
+  assert(st.size() >= 4);
+  assert(st.max_size() == (std::vector<std::stacktrace_entry, std::allocator<std::stacktrace_entry>>().max_size()));
+
+  /*
+    const_reference operator[](size_type frame_no) const;
+    Preconditions: frame_no < size() is true.
+    Returns: frames_[frame_no].
+    Throws: Nothing.
+  */
+  assert(st[0]);
+  assert(st[1]);
+  assert(st[2]);
+  assert(st[3]);
+
+  /*
+    const_reference at(size_type frame_no) const;
+    Returns: frames_[frame_no].
+    Throws: out_of_range if frame_no >= size().
+  */
+  assert(st.at(0));
+  assert(st.at(1));
+  assert(st.at(2));
+  assert(st.at(3));
+  try {
+    (void)st.at(42);
+    assert(false && "'at' should have thrown range_error");
+  } catch (std::out_of_range const&) {
+    // ok
+  }
+
+  auto f0 = st[0];
+  auto f1 = st[1];
+  auto f2 = st[2];
+  auto f3 = st[3];
+
+  auto fit = st.begin();
+  assert(*fit++ == f0);
+  assert(fit != st.end());
+
+  auto rit = st.rbegin();
+  assert(rit != st.rend());
+
+  return 0;
+}
diff --git a/libcxx/test/std/diagnostics/stacktrace/basic.pass.cpp b/libcxx/test/std/diagnostics/stacktrace/basic.pass.cpp
new file mode 100644
index 0000000000000..ce502626a45ea
--- /dev/null
+++ b/libcxx/test/std/diagnostics/stacktrace/basic.pass.cpp
@@ -0,0 +1,154 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++03, c++11, c++14, c++17, c++20
+
+#include <experimental/stacktrace>
+#include <iterator>
+
+#include <cassert>
+#include <type_traits>
+
+/*
+  (19.6.4) Class template basic_stacktrace [stacktrace.basic]
+  (19.6.4.1) Overview                      [stacktrace.basic.overview]
+
+namespace std {
+  template<class Allocator>
+  class basic_stacktrace {
+  public:
+    using value_type = stacktrace_entry;
+    using const_reference = const value_type&;
+    using reference = value_type&;
+    using const_iterator = implementation-defined;  // see [stacktrace.basic.obs]
+    using iterator = const_iterator;
+    using reverse_iterator = std::reverse_iterator<iterator>;
+    using const_reverse_iterator = std::reverse_iterator<const_iterator>;
+    using difference_type = implementation-defined;
+    using size_type = implementation-defined;
+    using allocator_type = Allocator;
+
+    // (19.6.4.2)
+    // [stacktrace.basic.cons], creation and assignment
+    static basic_stacktrace current(const allocator_type& alloc = allocator_type()) noexcept;
+    static basic_stacktrace current(size_type skip,
+                                    const allocator_type& alloc = allocator_type()) noexcept;
+    static basic_stacktrace current(size_type skip, size_type max_depth,
+                                    const allocator_type& alloc = allocator_type()) noexcept;
+
+    basic_stacktrace() noexcept(is_nothrow_default_constructible_v<allocator_type>);
+    explicit basic_stacktrace(const allocator_type& alloc) noexcept;
+
+    basic_stacktrace(const basic_stacktrace& other);
+    basic_stacktrace(basic_stacktrace&& other) noexcept;
+    basic_stacktrace(const basic_stacktrace& other, const allocator_type& alloc);
+    basic_stacktrace(basic_stacktrace&& other, const allocator_type& alloc);
+    basic_stacktrace& operator=(const basic_stacktrace& other);
+    basic_stacktrace& operator=(basic_stacktrace&& other)
+      noexcept(allocator_traits<Allocator>::propagate_on_container_move_assignment::value ||
+        allocator_traits<Allocator>::is_always_equal::value);
+
+    ~basic_stacktrace();
+
+    // (19.6.4.3)
+    // [stacktrace.basic.obs], observers
+    allocator_type get_allocator() const noexcept;
+
+    const_iterator begin() const noexcept;
+    const_iterator end() const noexcept;
+    const_reverse_iterator rbegin() const noexcept;
+    const_reverse_iterator rend() const noexcept;
+
+    const_iterator cbegin() const noexcept;
+    const_iterator cend() const noexcept;
+    const_reverse_iterator crbegin() const noexcept;
+    const_reverse_iterator crend() const noexcept;
+
+    bool empty() const noexcept;
+    size_type size() const noexcept;
+    size_type max_size() const noexcept;
+
+    const_reference operator[](size_type) const;
+    const_reference at(size_type) const;
+    
+    // (19.6.4.4)
+    // [stacktrace.basic.cmp], comparisons
+    template<class Allocator2>
+    friend bool operator==(const basic_stacktrace& x,
+                           const basic_stacktrace<Allocator2>& y) noexcept;
+    template<class Allocator2>
+    friend strong_ordering operator<=>(const basic_stacktrace& x,
+                                       const basic_stacktrace<Allocator2>& y) noexcept;
+
+    // (19.6.4.5)
+    // [stacktrace.basic.mod], modifiers
+    void swap(basic_stacktrace& other)
+      noexcept(allocator_traits<Allocator>::propagate_on_container_swap::value ||
+        allocator_traits<Allocator>::is_always_equal::value);
+
+  private:
+    vector<value_type, allocator_type> frames_;         // exposition only
+  };
+
+  // (19.6.4.6)
+  // [stacktrace.basic.nonmem], non-member functions
+
+  template<class Allocator>
+    void swap(basic_stacktrace<Allocator>& a, basic_stacktrace<Allocator>& b)
+      noexcept(noexcept(a.swap(b)));
+
+  string to_string(const stacktrace_entry& f);
+
+  template<class Allocator>
+    string to_string(const basic_stacktrace<Allocator>& st);
+
+  ostream& operator<<(ostream& os, const stacktrace_entry& f);
+  template<class Allocator>
+    ostream& operator<<(ostream& os, const basic_stacktrace<Allocator>& st);
+}
+
+*/
+
+int main(int, char**) {
+  // using value_type = stacktrace_entry;
+  // using const_reference = const value_type&;
+  // using reference = value_type&;
+  // using const_iterator = implementation-defined;  // see [stacktrace.basic.obs]
+  // using iterator = const_iterator;
+  // using reverse_iterator = std::reverse_iterator<iterator>;
+  // using const_reverse_iterator = std::reverse_iterator<const_iterator>;
+  // using difference_type = implementation-defined;
+  // using size_type = implementation-defined;
+  // using allocator_type = Allocator;
+
+  // This test will only verify these member types exist and are
+  // defined as expected; their actual behavior is tested in another .cpp.
+
+  using A = std::allocator<std::stacktrace_entry>;
+  using S = std::basic_stacktrace<A>;
+
+  static_assert(std::is_same_v<S::value_type, std::stacktrace_entry>);
+  static_assert(std::is_same_v<S::const_reference, std::stacktrace_entry const&>);
+  static_assert(std::is_same_v<S::reference, std::stacktrace_entry&>);
+
+  static_assert(std::forward_iterator<S::const_iterator>);
+  static_assert(std::forward_iterator<S::iterator>);
+  using CRI = S::const_reverse_iterator;
+  static_assert(std::is_same_v<CRI, decltype(S(A()).crbegin())>);
+  using RI = S::reverse_iterator;
+  static_assert(std::is_same_v<RI, decltype(S(A()).rbegin())>);
+
+  using IterT = S::iterator;
+  using DiffT = S::difference_type;
+  static_assert(std::is_same_v<IterT, decltype(IterT() + DiffT())>);
+
+  static_assert(std::is_integral_v<S::size_type>);
+  static_assert(std::is_same_v<S::allocator_type, A>);
+
+  return 0;
+}
diff --git a/libcxx/test/std/diagnostics/stacktrace/entry.cmp.pass.cpp b/libcxx/test/std/diagnostics/stacktrace/entry.cmp.pass.cpp
new file mode 100644
index 0000000000000..4c6531319fc09
--- /dev/null
+++ b/libcxx/test/std/diagnostics/stacktrace/entry.cmp.pass.cpp
@@ -0,0 +1,65 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++03, c++11, c++14, c++17, c++20
+
+#include <experimental/stacktrace>
+
+#include <cassert>
+
+/*
+  (19.6.3.5) Comparison [stacktrace.entry.cmp]
+
+namespace std {
+  class stacktrace_entry {
+  public:
+    // [stacktrace.entry.cmp], comparison
+    friend constexpr bool operator==(const stacktrace_entry& x,
+                                     const stacktrace_entry& y) noexcept;           // [T11]
+    friend constexpr strong_ordering operator<=>(const stacktrace_entry& x,
+                                                 const stacktrace_entry& y) noexcept;  // [T12]
+
+    [. . .]
+  };
+}
+*/
+
+int main(int, char**) {
+  // Two empty entries
+
+  std::stacktrace_entry a;
+  assert(a.native_handle() == 0);
+  assert(!a);
+
+  std::stacktrace_entry b;
+  assert(b.native_handle() == 0);
+  assert(!b);
+
+  // A non-empty entry.
+  std::stacktrace_entry c;
+  ((std::__stacktrace::entry*)(&c))->__addr_ = (uintptr_t)&main;
+  assert(c);
+
+  // [T11]
+  // friend constexpr bool operator==(const stacktrace_entry& x,
+  //                                  const stacktrace_entry& y) noexcept;
+  // "Returns: true if and only if x and y represent the same
+  // stacktrace entry or both x and y are empty."
+  // (We represent "empty" with a native_handle of zero.)
+  assert(a == b);
+  assert(a != c);
+
+  // [T12]
+  // friend constexpr strong_ordering operator<=>(const stacktrace_entry& x,
+  //                                              const stacktrace_entry& y) noexcept;
+  assert(std::strong_ordering::equal == (a <=> b));
+  assert(std::strong_ordering::equivalent == (a <=> b));
+  assert(std::strong_ordering::greater == (c <=> a));
+
+  return 0;
+}
diff --git a/libcxx/test/std/diagnostics/stacktrace/entry.cons.pass.cpp b/libcxx/test/std/diagnostics/stacktrace/entry.cons.pass.cpp
new file mode 100644
index 0000000000000..944b4c519f0fd
--- /dev/null
+++ b/libcxx/test/std/diagnostics/stacktrace/entry.cons.pass.cpp
@@ -0,0 +1,63 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++03, c++11, c++14, c++17, c++20
+// ADDITIONAL_COMPILE_FLAGS: -g
+
+#include <cassert>
+#include <experimental/stacktrace>
+#include <type_traits>
+
+/*
+  (19.6.3.2) Constructors [stacktrace.entry.cons]
+
+namespace std {
+  class stacktrace_entry {
+  public:
+    // [stacktrace.entry.cons], constructors
+    constexpr stacktrace_entry() noexcept;                                          // [T2]
+    constexpr stacktrace_entry(const stacktrace_entry& other) noexcept;             // [T3]
+    constexpr stacktrace_entry& operator=(const stacktrace_entry& other) noexcept;  // [T4]
+    ~stacktrace_entry();                                                            // [T5]
+
+    [. . .]
+  };
+}
+*/
+
+_LIBCPP_NO_TAIL_CALLS
+int main(int, char**) {
+  // [T2]
+  // constexpr stacktrace_entry() noexcept;
+  // "Postconditions: *this is empty."
+  static_assert(std::is_default_constructible_v<std::stacktrace_entry>);
+  static_assert(std::is_nothrow_default_constructible_v<std::stacktrace_entry>);
+  std::stacktrace_entry entry_t2;
+  assert(!entry_t2);
+
+  // [T3]
+  // constexpr stacktrace_entry(const stacktrace_entry& other) noexcept;
+  static_assert(std::is_nothrow_copy_constructible_v<std::stacktrace_entry>);
+  std::stacktrace_entry entry_t3(entry_t2);
+
+  // [T4]
+  // constexpr stacktrace_entry& operator=(const stacktrace_entry& other) noexcept;
+  static_assert(std::is_nothrow_copy_assignable_v<std::stacktrace_entry>);
+  std::stacktrace_entry entry_t4;
+  entry_t4 = entry_t2;
+
+  // [T5]
+  // ~stacktrace_entry();
+  std::stacktrace_entry* entry_ptr{nullptr};
+  delete entry_ptr;
+  {
+    auto entry_t5(entry_t4); /* construct and immediately let it go out of scope */
+  }
+
+  return 0;
+}
diff --git a/libcxx/test/std/diagnostics/stacktrace/entry.obs.pass.cpp b/libcxx/test/std/diagnostics/stacktrace/entry.obs.pass.cpp
new file mode 100644
index 0000000000000..da6e3ccec92b6
--- /dev/null
+++ b/libcxx/test/std/diagnostics/stacktrace/entry.obs.pass.cpp
@@ -0,0 +1,51 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++03, c++11, c++14, c++17, c++20
+
+#include <experimental/stacktrace>
+
+#include <cassert>
+
+/*
+  (19.6.3.3) Observers [stacktrace.entry.obs]
+
+namespace std {
+  class stacktrace_entry {
+    // [stacktrace.entry.obs], observers
+    constexpr native_handle_type native_handle() const noexcept;                    // [T6]
+    constexpr explicit operator bool() const noexcept;                              // [T7]
+    
+    [. . .]
+  };
+}
+*/
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+namespace __stacktrace {}
+_LIBCPP_END_NAMESPACE_STD
+
+int main(int, char**) {
+  // [T6]
+  std::stacktrace_entry entry_t6;
+
+  // constexpr native_handle_type native_handle() const noexcept;
+  assert(entry_t6.native_handle() == 0);
+
+  // [T7]
+  // constexpr explicit operator bool() const noexcept;
+  // "Returns: false if and only if *this is empty."
+  assert(!entry_t6);
+
+  // Now set addr to something nonzero
+  ((std::__stacktrace::entry*)(&entry_t6))->__addr_ = (uintptr_t)&main;
+  assert(entry_t6.native_handle() == (uintptr_t)&main);
+  assert(entry_t6);
+
+  return 0;
+}
diff --git a/libcxx/test/std/diagnostics/stacktrace/entry.pass.cpp b/libcxx/test/std/diagnostics/stacktrace/entry.pass.cpp
new file mode 100644
index 0000000000000..b55bdcde966d3
--- /dev/null
+++ b/libcxx/test/std/diagnostics/stacktrace/entry.pass.cpp
@@ -0,0 +1,66 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++03, c++11, c++14, c++17, c++20
+
+#include <experimental/stacktrace>
+
+#include <cassert>
+#include <concepts>
+#include <cstddef>
+
+/*
+  (19.6.3) Class stacktrace_entry         [stacktrace.entry]
+  (19.6.3.1) Overview                     [stacktrace.entry.overview]
+
+namespace std {
+  class stacktrace_entry {
+  public:
+    using native_handle_type = implementation-defined;                              // [T1] [entry.pass.cpp]
+
+    // [stacktrace.entry.cons], constructors
+    constexpr stacktrace_entry() noexcept;                                          // [T2] [entry.cons.pass.cpp]
+    constexpr stacktrace_entry(const stacktrace_entry& other) noexcept;             // [T3]
+    constexpr stacktrace_entry& operator=(const stacktrace_entry& other) noexcept;  // [T4]
+    ~stacktrace_entry();                                                            // [T5]
+
+    // [stacktrace.entry.obs], observers
+    constexpr native_handle_type native_handle() const noexcept;                    // [T6] [entry.obs.pass.cpp]
+    constexpr explicit operator bool() const noexcept;                              // [T7]
+
+    // [stacktrace.entry.query], query
+    string description() const;                                                     // [T8] [entry.query.pass.cpp]
+    string source_file() const;                                                     // [T9]
+    uint_least32_t source_line() const;                                             // [T10]
+
+    // [stacktrace.entry.cmp], comparison
+    friend constexpr bool operator==(const stacktrace_entry& x,
+                                     const stacktrace_entry& y) noexcept;           // [T11] [entry.cmp.pass.cpp]
+    friend constexpr strong_ordering operator<=>(const stacktrace_entry& x,
+                                                 const stacktrace_entry& y) noexcept;  // [T12]
+  };
+}
+*/
+
+int main(int, char**) {
+  // [stacktrace.entry.overview]
+  // "The class stacktrace_entry models regular ([concepts.object])
+  // and three_way_comparable<strong_ordering> ([cmp.concept])."
+  static_assert(std::regular<std::stacktrace_entry>);
+  static_assert(std::three_way_comparable<std::stacktrace_entry, std::strong_ordering>);
+
+  // [T1]
+  // using native_handle_type = implementation-defined;
+  //
+  // [Implementation note: For our purposes anything that unique identifies this stacktrace_entry
+  // would be good enough.  We'll use a pointer-sized numeric type (to represent location of the
+  // calling instruction).  Internally this is defined as `uintptr_t`.]
+  static_assert(sizeof(std::stacktrace_entry::native_handle_type) >= sizeof(void*));
+
+  return 0;
+}
diff --git a/libcxx/test/std/diagnostics/stacktrace/entry.query.pass.cpp b/libcxx/test/std/diagnostics/stacktrace/entry.query.pass.cpp
new file mode 100644
index 0000000000000..bfdb54e4df668
--- /dev/null
+++ b/libcxx/test/std/diagnostics/stacktrace/entry.query.pass.cpp
@@ -0,0 +1,85 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++03, c++11, c++14, c++17, c++20
+// ADDITIONAL_COMPILE_FLAGS: -O0 -g -gsplit-dwarf
+
+#include <experimental/stacktrace>
+
+#include <cassert>
+#include <iostream>
+#include <string>
+
+/*
+    (19.6.3.4) Query [stacktrace.entry.query]
+
+namespace std {
+  class stacktrace_entry {
+  public:
+    // [stacktrace.entry.query], query
+    string description() const;                                                     // [T8]
+    string source_file() const;                                                     // [T9]
+    uint_least32_t source_line() const;                                             // [T10]
+
+    [. . .]
+  };
+}
+*/
+
+int main(int, char**) {
+  // empty trace entry
+  std::stacktrace_entry e;
+
+  // [T8]
+  // string description() const;
+  auto desc = e.description();
+  assert(desc.c_str()[0] == 0);
+  assert(desc.size() == 0);
+
+  // [T9]
+  // string source_file() const;
+  auto src = e.source_file();
+  assert(src.c_str()[0] == 0);
+  assert(src.size() == 0);
+
+  // [T10]
+  // uint_least32_t source_line() const;
+  assert(e.source_line() == 0);
+
+  // Get the current trace.
+  uint32_t line_number = __LINE__ + 1; // record where `current` is being called:
+  auto trace           = std::stacktrace::current();
+
+  // First entry of this should be `main`.
+  e = trace.at(0);
+  assert(e);
+
+  std::cout << "main is at:      " << (void*)&main << std::endl;
+  std::cout << "e.native_handle: " << (void*)e.native_handle() << std::endl;
+  std::cout << "e.description:   " << e.description() << std::endl;
+  std::cout << "e.source_file:   " << e.source_file() << std::endl;
+  std::cout << "e.source_line:   " << e.source_line() << std::endl;
+
+  std::cout << trace << std::endl;
+
+  assert(e.native_handle());
+  assert(e.native_handle() >= (uintptr_t)&main);
+  assert(e.description() == "main" || e.description() == "_main");
+  // Even if we cannot get the debug info or call out to llvm-addr2line,
+  // we should at least get the executable filename, e.g. `entry.query.pass.cpp.dir/t.exe`
+  assert(!e.source_file().empty());
+  assert(e.source_file().contains("entry.query.pass.cpp"));
+
+  // These might not work at testing time, so disable.
+  // Complete tests checking the filename:line part are in `std/diagnostics/stacktrace`
+  //   assert(e.source_file().ends_with("entry.query.pass.cpp"));
+  //   assert(e.source_line() == line_number);
+  (void)line_number;
+
+  return 0;
+}
diff --git a/libcxx/test/std/diagnostics/stacktrace/format.pass.cpp b/libcxx/test/std/diagnostics/stacktrace/format.pass.cpp
new file mode 100644
index 0000000000000..b37681659d43c
--- /dev/null
+++ b/libcxx/test/std/diagnostics/stacktrace/format.pass.cpp
@@ -0,0 +1,53 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++03, c++11, c++14, c++17, c++20
+
+#include <cassert>
+#include <experimental/stacktrace>
+
+/*
+  (19.6.5) Formatting support [stacktrace.format]
+
+  template<> struct formatter<stacktrace_entry>;                            [1]
+  template<class Allocator> struct formatter<basic_stacktrace<Allocator>>;  [2]
+*/
+
+int main(int, char**) {
+  /*
+    [1]
+    template<> struct formatter<stacktrace_entry>;
+
+    formatter<stacktrace_entry> interprets format-spec as a stacktrace-entry-format-spec.
+    The syntax of format specifications is as follows:
+
+      stacktrace-entry-format-spec :
+        fill-and-align_[opt] width_[opt]
+
+    [Note 1: The productions fill-and-align and width are described in [format.string.std]. — end note]
+
+    A stacktrace_entry object se is formatted as if by copying to_string(se) through the output iterator
+    of the context with additional padding and adjustments as specified by the format specifiers.
+  */
+
+  // TODO(stacktrace23): needs `formatter`
+
+  /*
+    [2]
+    template<class Allocator> struct formatter<basic_stacktrace<Allocator>>;
+    
+    For formatter<basic_stacktrace<Allocator>>, format-spec is empty.
+    
+    A basic_stacktrace<Allocator> object s is formatted as if by copying to_string(s) through the
+    output iterator of the context.
+  */
+
+  // TODO(stacktrace23): needs `formatter`
+
+  return 0;
+}
diff --git a/libcxx/test/std/diagnostics/stacktrace/syn.pass.cpp b/libcxx/test/std/diagnostics/stacktrace/syn.pass.cpp
new file mode 100644
index 0000000000000..3c92016b2c900
--- /dev/null
+++ b/libcxx/test/std/diagnostics/stacktrace/syn.pass.cpp
@@ -0,0 +1,147 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++03, c++11, c++14, c++17, c++20
+
+#include <cassert>
+#include <experimental/stacktrace>
+
+#include <memory>
+#include <type_traits>
+
+/*
+
+// (19.6.2) Header <stacktrace> synopsis [stacktrace.syn]
+
+namespace std {
+
+  // [stacktrace.entry], class stacktrace_entry
+  class stacktrace_entry;                                               [1]
+
+  // [stacktrace.basic], class template basic_stacktrace
+  template<class Allocator>
+    class basic_stacktrace;                                             [2]
+
+  // basic_stacktrace typedef-names
+  using stacktrace = basic_stacktrace<allocator<stacktrace_entry>>;     [3]
+
+  // [stacktrace.basic.nonmem], non-member functions
+  template<class Allocator>
+    void swap(basic_stacktrace<Allocator>& a,
+              basic_stacktrace<Allocator>& b)
+                noexcept(noexcept(a.swap(b)));                          [4]
+
+  string to_string(const stacktrace_entry& f);                          [5]
+
+  template<class Allocator>
+    string to_string(const basic_stacktrace<Allocator>& st);            [6]
+
+  ostream& operator<<(ostream& os, const stacktrace_entry& f);          [7]
+  template<class Allocator>
+    ostream& operator<<(ostream& os,
+                        const basic_stacktrace<Allocator>& st);         [8]
+
+  // [stacktrace.format], formatting support
+  template<> struct formatter<stacktrace_entry>;                        [9]
+  template<class Allocator>
+    struct formatter<basic_stacktrace<Allocator>>;                      [10]
+
+  namespace pmr {
+    using stacktrace =
+        basic_stacktrace<polymorphic_allocator<stacktrace_entry>>;      [11]
+  }
+
+  // [stacktrace.basic.hash], hash support
+  template<> struct hash<stacktrace_entry>;                             [12]
+  template<class Allocator> struct hash<basic_stacktrace<Allocator>>;   [13]
+}
+*/
+
+// static_assert(__cpp_lib_stacktrace == 202011L);
+
+int main(int, char**) {
+  // Very basic tests to ensure the required things are declared.
+  // Only checking for types' and functions' existence, parameter and return types,
+  // and type-completeness.  Functional tests exist in the other .cpp's in this directory.
+
+  using Alloc = std::allocator<std::stacktrace_entry>;
+
+  // [1]
+  // [stacktrace.entry], class stacktrace_entry
+  // class stacktrace_entry;
+  using T1 = std::stacktrace_entry;
+  assert(std::is_constructible_v<T1>);
+
+  // [2]
+  // [stacktrace.basic], class template basic_stacktrace
+  // template<class Allocator>
+  //   class basic_stacktrace;
+  using T2 = std::basic_stacktrace<Alloc>;
+  assert(std::is_constructible_v<T2>);
+
+  // [3]
+  // basic_stacktrace typedef-names
+  // using stacktrace = basic_stacktrace<allocator<stacktrace_entry>>;
+  using T3 = std::stacktrace;
+  static_assert(std::is_same_v<T3, std::basic_stacktrace<std::allocator<std::stacktrace_entry>>>);
+
+  // [4]
+  // [stacktrace.basic.nonmem], non-member functions
+  // template<class Allocator>
+  //   void swap(basic_stacktrace<Allocator>& a, basic_stacktrace<Allocator>& b)
+  //     noexcept(noexcept(a.swap(b)));
+  std::basic_stacktrace<Alloc> a;
+  std::basic_stacktrace<Alloc> b;
+  std::swap(a, b);
+
+  // [5]
+  // string to_string(const stacktrace_entry& f);
+  using T5 = decltype(std::to_string(std::stacktrace_entry()));
+  static_assert(std::is_same_v<std::string, T5>);
+
+  // [6]
+  // template<class Allocator>
+  // string to_string(const basic_stacktrace<Allocator>& st);
+  using T6 = decltype(std::to_string(std::basic_stacktrace<Alloc>()));
+  static_assert(std::is_same_v<std::string, T6>);
+
+  // [7]
+  // ostream& operator<<(ostream& os, const stacktrace_entry& f);
+  std::ostream* os;
+  using T7 = decltype(operator<<(*os, std::stacktrace_entry()));
+  static_assert(std::is_same_v<std::ostream&, T7>);
+
+  // [8]
+  // template<class Allocator>
+  //   ostream& operator<<(ostream& os, const basic_stacktrace<Allocator>& st);
+  using T8 = decltype(operator<<(*os, std::basic_stacktrace<Alloc>()));
+  static_assert(std::is_same_v<std::ostream&, T8>);
+
+  // [9]
+  // template<> struct formatter<stacktrace_entry>;
+  //   using T9 = std::formatter<std::stacktrace_entry>;
+  //   static_assert(std::is_constructible_v<T9>);
+
+  // TODO(stacktrace23): needs `formatter`
+
+  // [10]
+  // template<class Allocator> struct formatter<basic_stacktrace<Allocator>>;
+  //   using T10 = std::formatter<std::basic_stacktrace<Alloc>>;
+  //   static_assert(std::is_constructible_v<T10>);
+
+  // TODO(stacktrace23): needs `formatter`
+
+  // [11]
+  // namespace pmr { using stacktrace = basic_stacktrace<polymorphic_allocator<stacktrace_entry>>; }
+  using AllocPMR = std::pmr::polymorphic_allocator<std::stacktrace_entry>;
+  using BasicPMR = std::basic_stacktrace<AllocPMR>;
+  using T11      = std::pmr::stacktrace;
+  static_assert(std::is_same_v<T11, BasicPMR>);
+
+  return 0;
+}
diff --git a/libcxx/utils/libcxx/header_information.py b/libcxx/utils/libcxx/header_information.py
index a505d37b65b81..6d69cf29af308 100644
--- a/libcxx/utils/libcxx/header_information.py
+++ b/libcxx/utils/libcxx/header_information.py
@@ -170,7 +170,7 @@ def __hash__(self) -> int:
     "linalg",
     "rcu",
     "spanstream",
-    "stacktrace",
+    "stacktrace",  # TODO(stacktrace23): remove this when stacktrace is taken out of experimental
     "stdfloat",
     "text_encoding",
 ]))
@@ -208,6 +208,7 @@ def __hash__(self) -> int:
     "experimental/iterator": "// UNSUPPORTED: c++03",
     "experimental/propagate_const": "// UNSUPPORTED: c++03",
     "experimental/simd": "// UNSUPPORTED: c++03",
+    "experimental/stacktrace": "// UNSUPPORTED: c++03, c++11, c++14, c++17, c++20",
     "experimental/type_traits": "// UNSUPPORTED: c++03",
     "experimental/utility": "// UNSUPPORTED: c++03",
     "filesystem": "// UNSUPPORTED: no-filesystem, c++03, c++11, c++14",
@@ -275,6 +276,7 @@ def __hash__(self) -> int:
     "regex": ["compare", "initializer_list"],
     "set": ["compare", "initializer_list"],
     "stack": ["compare", "initializer_list"],
+    "stacktrace": ["compare"],
     "string_view": ["compare"],
     "string": ["compare", "initializer_list"],
     "syncstream": ["ostream"],
diff --git a/llvm/utils/gn/secondary/libcxx/src/BUILD.gn b/llvm/utils/gn/secondary/libcxx/src/BUILD.gn
index 2bc851a99afb1..9e045d2971179 100644
--- a/llvm/utils/gn/secondary/libcxx/src/BUILD.gn
+++ b/llvm/utils/gn/secondary/libcxx/src/BUILD.gn
@@ -317,6 +317,40 @@ if (libcxx_enable_experimental) {
     output_dir = runtimes_dir
     output_name = "c++experimental"
     sources = [ "experimental/keep.cpp" ]
+    sources += [
+      "experimental/stacktrace/alloc.cpp",
+      "experimental/stacktrace/common/config.h",
+      "experimental/stacktrace/common/debug.cpp",
+      "experimental/stacktrace/common/debug.h",
+      "experimental/stacktrace/common/failed.h",
+      "experimental/stacktrace/common/fd.cpp",
+      "experimental/stacktrace/common/fd.h",
+      "experimental/stacktrace/common/images.h",
+      "experimental/stacktrace/context.cpp",
+      "experimental/stacktrace/linux/linux-dl.cpp",
+      "experimental/stacktrace/linux/linux-elf.cpp",
+      "experimental/stacktrace/linux/linux-sym.cpp",
+      "experimental/stacktrace/linux/linux.h",
+      "experimental/stacktrace/osx/osx.cpp",
+      "experimental/stacktrace/osx/osx.h",
+      "experimental/stacktrace/stacktrace.cpp",
+      "experimental/stacktrace/tools/addr2line.cpp",
+      "experimental/stacktrace/tools/atos.cpp",
+      "experimental/stacktrace/tools/llvm_symbolizer.cpp",
+      "experimental/stacktrace/tools/pspawn.h",
+      "experimental/stacktrace/tools/tools.h",
+      "experimental/stacktrace/tools/toolspawner.cpp",
+      "experimental/stacktrace/unwind/unwind.cpp",
+      "experimental/stacktrace/unwind/unwind.h",
+      "experimental/stacktrace/windows/dbghelp_dll.cpp",
+      "experimental/stacktrace/windows/dbghelp_dll.h",
+      "experimental/stacktrace/windows/dll.cpp",
+      "experimental/stacktrace/windows/dll.h",
+      "experimental/stacktrace/windows/psapi_dll.cpp",
+      "experimental/stacktrace/windows/psapi_dll.h",
+      "experimental/stacktrace/windows/win_impl.cpp",
+      "experimental/stacktrace/windows/win_impl.h",
+    ]
     if (libcxx_enable_filesystem && libcxx_enable_time_zone_database) {
       sources += [
         # TODO TZDB The exception could be moved in chrono once the TZDB library

>From 25e2db9605519f9ea0ed1702e5bf529c83454242 Mon Sep 17 00:00:00 2001
From: Steve O'Brien <steve at obrien.cc>
Date: Sun, 20 Apr 2025 23:48:58 -0400
Subject: [PATCH 2/4] Remove unrelated change

---
 libcxx/include/__ostream/basic_ostream.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/libcxx/include/__ostream/basic_ostream.h b/libcxx/include/__ostream/basic_ostream.h
index 891dddbf79c42..f7473a36d8ccc 100644
--- a/libcxx/include/__ostream/basic_ostream.h
+++ b/libcxx/include/__ostream/basic_ostream.h
@@ -570,7 +570,7 @@ _LIBCPP_HIDE_FROM_ABI _Stream&& operator<<(_Stream&& __os, const _Tp& __x) {
 }
 
 template <class _CharT, class _Traits, class _Allocator>
-_LIBCPP_HIDE_FROM_ABI basic_ostream<_CharT, _Traits>&
+basic_ostream<_CharT, _Traits>&
 operator<<(basic_ostream<_CharT, _Traits>& __os, const basic_string<_CharT, _Traits, _Allocator>& __str) {
   return std::__put_character_sequence(__os, __str.data(), __str.size());
 }

>From 2c76684de0c5ae698767536a1b973da5095a3881 Mon Sep 17 00:00:00 2001
From: Steve O'Brien <steve at obrien.cc>
Date: Mon, 21 Apr 2025 19:26:15 -0400
Subject: [PATCH 3/4] Move stacktrace headers out of experimental

---
 libcxx/include/CMakeLists.txt                 | 14 ++--
 .../__stacktrace/basic_stacktrace.h           |  6 +-
 .../__stacktrace/detail/alloc.h               |  0
 .../__stacktrace/detail/context.h             |  0
 .../__stacktrace/detail/entry.h               |  0
 .../__stacktrace/detail/to_string.h           |  0
 .../__stacktrace/stacktrace_entry.h           |  2 +-
 libcxx/include/module.modulemap.in            | 21 +++---
 libcxx/include/{experimental => }/stacktrace  |  4 +-
 libcxx/modules/std.compat.cppm.in             |  5 +-
 libcxx/modules/std.cppm.in                    |  3 -
 llvm/utils/gn/secondary/libcxx/src/BUILD.gn   | 66 +++++++++----------
 12 files changed, 57 insertions(+), 64 deletions(-)
 rename libcxx/include/{experimental => }/__stacktrace/basic_stacktrace.h (98%)
 rename libcxx/include/{experimental => }/__stacktrace/detail/alloc.h (100%)
 rename libcxx/include/{experimental => }/__stacktrace/detail/context.h (100%)
 rename libcxx/include/{experimental => }/__stacktrace/detail/entry.h (100%)
 rename libcxx/include/{experimental => }/__stacktrace/detail/to_string.h (100%)
 rename libcxx/include/{experimental => }/__stacktrace/stacktrace_entry.h (98%)
 rename libcxx/include/{experimental => }/stacktrace (98%)

diff --git a/libcxx/include/CMakeLists.txt b/libcxx/include/CMakeLists.txt
index ef091e40b9ec8..65b69674433f4 100644
--- a/libcxx/include/CMakeLists.txt
+++ b/libcxx/include/CMakeLists.txt
@@ -727,6 +727,12 @@ set(files
   __ranges/views.h
   __ranges/zip_view.h
   __split_buffer
+  __stacktrace/basic_stacktrace.h
+  __stacktrace/detail/alloc.h
+  __stacktrace/detail/context.h
+  __stacktrace/detail/entry.h
+  __stacktrace/detail/to_string.h
+  __stacktrace/stacktrace_entry.h
   __std_mbstate_t.h
   __stop_token/atomic_unique_lock.h
   __stop_token/intrusive_list_view.h
@@ -991,17 +997,10 @@ set(files
   experimental/__simd/traits.h
   experimental/__simd/utility.h
   experimental/__simd/vec_ext.h
-  experimental/__stacktrace/basic_stacktrace.h
-  experimental/__stacktrace/detail/alloc.h
-  experimental/__stacktrace/detail/context.h
-  experimental/__stacktrace/detail/entry.h
-  experimental/__stacktrace/detail/to_string.h
-  experimental/__stacktrace/stacktrace_entry.h
   experimental/iterator
   experimental/memory
   experimental/propagate_const
   experimental/simd
-  experimental/stacktrace
   experimental/type_traits
   experimental/utility
   ext/__hash
@@ -1054,6 +1053,7 @@ set(files
   span
   sstream
   stack
+  stacktrace
   stdatomic.h
   stdbool.h
   stddef.h
diff --git a/libcxx/include/experimental/__stacktrace/basic_stacktrace.h b/libcxx/include/__stacktrace/basic_stacktrace.h
similarity index 98%
rename from libcxx/include/experimental/__stacktrace/basic_stacktrace.h
rename to libcxx/include/__stacktrace/basic_stacktrace.h
index 8ac1de82b1c63..cad3571d559bc 100644
--- a/libcxx/include/experimental/__stacktrace/basic_stacktrace.h
+++ b/libcxx/include/__stacktrace/basic_stacktrace.h
@@ -37,9 +37,9 @@
 #include <memory>
 #include <string>
 
-#include <experimental/__stacktrace/detail/alloc.h>
-#include <experimental/__stacktrace/detail/context.h>
-#include <experimental/__stacktrace/detail/to_string.h>
+#include <__stacktrace/detail/alloc.h>
+#include <__stacktrace/detail/context.h>
+#include <__stacktrace/detail/to_string.h>
 
 _LIBCPP_BEGIN_NAMESPACE_STD
 
diff --git a/libcxx/include/experimental/__stacktrace/detail/alloc.h b/libcxx/include/__stacktrace/detail/alloc.h
similarity index 100%
rename from libcxx/include/experimental/__stacktrace/detail/alloc.h
rename to libcxx/include/__stacktrace/detail/alloc.h
diff --git a/libcxx/include/experimental/__stacktrace/detail/context.h b/libcxx/include/__stacktrace/detail/context.h
similarity index 100%
rename from libcxx/include/experimental/__stacktrace/detail/context.h
rename to libcxx/include/__stacktrace/detail/context.h
diff --git a/libcxx/include/experimental/__stacktrace/detail/entry.h b/libcxx/include/__stacktrace/detail/entry.h
similarity index 100%
rename from libcxx/include/experimental/__stacktrace/detail/entry.h
rename to libcxx/include/__stacktrace/detail/entry.h
diff --git a/libcxx/include/experimental/__stacktrace/detail/to_string.h b/libcxx/include/__stacktrace/detail/to_string.h
similarity index 100%
rename from libcxx/include/experimental/__stacktrace/detail/to_string.h
rename to libcxx/include/__stacktrace/detail/to_string.h
diff --git a/libcxx/include/experimental/__stacktrace/stacktrace_entry.h b/libcxx/include/__stacktrace/stacktrace_entry.h
similarity index 98%
rename from libcxx/include/experimental/__stacktrace/stacktrace_entry.h
rename to libcxx/include/__stacktrace/stacktrace_entry.h
index be8abb3ea91b2..f06fb0b6d4cb1 100644
--- a/libcxx/include/experimental/__stacktrace/stacktrace_entry.h
+++ b/libcxx/include/__stacktrace/stacktrace_entry.h
@@ -33,7 +33,7 @@
 #include <cstdint>
 #include <string>
 
-#include "experimental/__stacktrace/detail/entry.h"
+#include <__stacktrace/detail/entry.h>
 
 _LIBCPP_BEGIN_NAMESPACE_STD
 
diff --git a/libcxx/include/module.modulemap.in b/libcxx/include/module.modulemap.in
index 8867681832bcf..4491768cfe935 100644
--- a/libcxx/include/module.modulemap.in
+++ b/libcxx/include/module.modulemap.in
@@ -1985,6 +1985,17 @@ module std [system] {
     export *
   }
 
+  module stacktrace {
+    module basic_stacktrace { header "__stacktrace/basic_stacktrace.h" }
+    module alloc { header "__stacktrace/detail/alloc.h" }
+    module context { header "__stacktrace/detail/context.h" }
+    module entry { header "__stacktrace/detail/entry.h" }
+    module to_string { header "__stacktrace/detail/to_string.h" }
+    module stacktrace_entry { header "__stacktrace/stacktrace_entry.h" }
+    header "stacktrace"
+    export *
+  }
+
   module stdexcept {
     header "stdexcept"
     export *
@@ -2225,16 +2236,6 @@ module std [system] {
       header "experimental/simd"
       export *
     }
-    module stacktrace {
-      private header "experimental/__stacktrace/basic_stacktrace.h"
-      private header "experimental/__stacktrace/detail/alloc.h"
-      private header "experimental/__stacktrace/detail/context.h"
-      private header "experimental/__stacktrace/detail/entry.h"
-      private header "experimental/__stacktrace/detail/to_string.h"
-      private header "experimental/__stacktrace/stacktrace_entry.h"
-      header "experimental/stacktrace"
-      export *
-    }
   }
 
   // Implementation detail headers that are private to libc++. These modules
diff --git a/libcxx/include/experimental/stacktrace b/libcxx/include/stacktrace
similarity index 98%
rename from libcxx/include/experimental/stacktrace
rename to libcxx/include/stacktrace
index 9e1f7259ca3da..33415533c2eea 100644
--- a/libcxx/include/experimental/stacktrace
+++ b/libcxx/include/stacktrace
@@ -180,8 +180,8 @@ namespace std {
 _LIBCPP_PUSH_MACROS
 #    include <__undef_macros>
 
-#    include "experimental/__stacktrace/basic_stacktrace.h"
-#    include "experimental/__stacktrace/stacktrace_entry.h"
+#    include <__stacktrace/basic_stacktrace.h>
+#    include <__stacktrace/stacktrace_entry.h>
 
 _LIBCPP_POP_MACROS
 
diff --git a/libcxx/modules/std.compat.cppm.in b/libcxx/modules/std.compat.cppm.in
index 95931447ccdc6..2ee56c6b810c9 100644
--- a/libcxx/modules/std.compat.cppm.in
+++ b/libcxx/modules/std.compat.cppm.in
@@ -71,9 +71,6 @@ module;
 #  if __has_include(<spanstream>)
 #    error "please update the header information for <spanstream> in headers_not_available in utils/libcxx/header_information.py"
 #  endif // __has_include(<spanstream>)
-#  if __has_include(<stacktrace>)
-#    error "please update the header information for <stacktrace> in headers_not_available in utils/libcxx/header_information.py"
-#  endif // __has_include(<stacktrace>)
 #  if __has_include(<stdfloat>)
 #    error "please update the header information for <stdfloat> in headers_not_available in utils/libcxx/header_information.py"
 #  endif // __has_include(<stdfloat>)
@@ -86,4 +83,4 @@ export module std.compat;
 export import std;
 
 
- at LIBCXX_MODULE_STD_COMPAT_INCLUDE_SOURCES@
\ No newline at end of file
+ at LIBCXX_MODULE_STD_COMPAT_INCLUDE_SOURCES@
diff --git a/libcxx/modules/std.cppm.in b/libcxx/modules/std.cppm.in
index 5c523691bff4e..dc40af57e573a 100644
--- a/libcxx/modules/std.cppm.in
+++ b/libcxx/modules/std.cppm.in
@@ -181,9 +181,6 @@ module;
 #  if __has_include(<spanstream>)
 #    error "please update the header information for <spanstream> in headers_not_available in utils/libcxx/header_information.py"
 #  endif // __has_include(<spanstream>)
-#  if __has_include(<stacktrace>)
-#    error "please update the header information for <stacktrace> in headers_not_available in utils/libcxx/header_information.py"
-#  endif // __has_include(<stacktrace>)
 #  if __has_include(<stdfloat>)
 #    error "please update the header information for <stdfloat> in headers_not_available in utils/libcxx/header_information.py"
 #  endif // __has_include(<stdfloat>)
diff --git a/llvm/utils/gn/secondary/libcxx/src/BUILD.gn b/llvm/utils/gn/secondary/libcxx/src/BUILD.gn
index 9e045d2971179..d30d70ac40842 100644
--- a/llvm/utils/gn/secondary/libcxx/src/BUILD.gn
+++ b/llvm/utils/gn/secondary/libcxx/src/BUILD.gn
@@ -167,6 +167,38 @@ cxx_sources = [
   "ryu/d2s.cpp",
   "ryu/f2s.cpp",
   "shared_mutex.cpp",
+  # "stacktrace/alloc.cpp",
+  # "stacktrace/common/config.h",
+  # "stacktrace/common/debug.cpp",
+  # "stacktrace/common/debug.h",
+  # "stacktrace/common/failed.h",
+  # "stacktrace/common/fd.cpp",
+  # "stacktrace/common/fd.h",
+  # "stacktrace/common/images.h",
+  # "stacktrace/context.cpp",
+  # "stacktrace/linux/linux-dl.cpp",
+  # "stacktrace/linux/linux-elf.cpp",
+  # "stacktrace/linux/linux-sym.cpp",
+  # "stacktrace/linux/linux.h",
+  # "stacktrace/osx/osx.cpp",
+  # "stacktrace/osx/osx.h",
+  # "stacktrace/stacktrace.cpp",
+  # "stacktrace/tools/addr2line.cpp",
+  # "stacktrace/tools/atos.cpp",
+  # "stacktrace/tools/llvm_symbolizer.cpp",
+  # "stacktrace/tools/pspawn.h",
+  # "stacktrace/tools/tools.h",
+  # "stacktrace/tools/toolspawner.cpp",
+  # "stacktrace/unwind/unwind.cpp",
+  # "stacktrace/unwind/unwind.h",
+  # "stacktrace/windows/dbghelp_dll.cpp",
+  # "stacktrace/windows/dbghelp_dll.h",
+  # "stacktrace/windows/dll.cpp",
+  # "stacktrace/windows/dll.h",
+  # "stacktrace/windows/psapi_dll.cpp",
+  # "stacktrace/windows/psapi_dll.h",
+  # "stacktrace/windows/win_impl.cpp",
+  # "stacktrace/windows/win_impl.h",
   "stdexcept.cpp",
   "string.cpp",
   "strstream.cpp",
@@ -317,40 +349,6 @@ if (libcxx_enable_experimental) {
     output_dir = runtimes_dir
     output_name = "c++experimental"
     sources = [ "experimental/keep.cpp" ]
-    sources += [
-      "experimental/stacktrace/alloc.cpp",
-      "experimental/stacktrace/common/config.h",
-      "experimental/stacktrace/common/debug.cpp",
-      "experimental/stacktrace/common/debug.h",
-      "experimental/stacktrace/common/failed.h",
-      "experimental/stacktrace/common/fd.cpp",
-      "experimental/stacktrace/common/fd.h",
-      "experimental/stacktrace/common/images.h",
-      "experimental/stacktrace/context.cpp",
-      "experimental/stacktrace/linux/linux-dl.cpp",
-      "experimental/stacktrace/linux/linux-elf.cpp",
-      "experimental/stacktrace/linux/linux-sym.cpp",
-      "experimental/stacktrace/linux/linux.h",
-      "experimental/stacktrace/osx/osx.cpp",
-      "experimental/stacktrace/osx/osx.h",
-      "experimental/stacktrace/stacktrace.cpp",
-      "experimental/stacktrace/tools/addr2line.cpp",
-      "experimental/stacktrace/tools/atos.cpp",
-      "experimental/stacktrace/tools/llvm_symbolizer.cpp",
-      "experimental/stacktrace/tools/pspawn.h",
-      "experimental/stacktrace/tools/tools.h",
-      "experimental/stacktrace/tools/toolspawner.cpp",
-      "experimental/stacktrace/unwind/unwind.cpp",
-      "experimental/stacktrace/unwind/unwind.h",
-      "experimental/stacktrace/windows/dbghelp_dll.cpp",
-      "experimental/stacktrace/windows/dbghelp_dll.h",
-      "experimental/stacktrace/windows/dll.cpp",
-      "experimental/stacktrace/windows/dll.h",
-      "experimental/stacktrace/windows/psapi_dll.cpp",
-      "experimental/stacktrace/windows/psapi_dll.h",
-      "experimental/stacktrace/windows/win_impl.cpp",
-      "experimental/stacktrace/windows/win_impl.h",
-    ]
     if (libcxx_enable_filesystem && libcxx_enable_time_zone_database) {
       sources += [
         # TODO TZDB The exception could be moved in chrono once the TZDB library

>From c199a8427b045b1fdee5582500b91bfdc4e68d82 Mon Sep 17 00:00:00 2001
From: Steve O'Brien <steve at obrien.cc>
Date: Mon, 21 Apr 2025 09:50:29 -0400
Subject: [PATCH 4/4] TEMPORARY action yaml for local repo

---
 .github/workflows/libcxx-build-and-test.yaml | 20 ++++++++++----------
 1 file changed, 10 insertions(+), 10 deletions(-)

diff --git a/.github/workflows/libcxx-build-and-test.yaml b/.github/workflows/libcxx-build-and-test.yaml
index fce20d6d9de05..13b3474bef11a 100644
--- a/.github/workflows/libcxx-build-and-test.yaml
+++ b/.github/workflows/libcxx-build-and-test.yaml
@@ -14,7 +14,7 @@
 #
 name: Build and Test libc++
 on:
-  pull_request:
+  push:
     paths:
       - 'libcxx/**'
       - 'libcxxabi/**'
@@ -22,9 +22,9 @@ on:
       - 'runtimes/**'
       - 'cmake/**'
       - '.github/workflows/libcxx-build-and-test.yaml'
-  schedule:
-    # Run nightly at 08:00 UTC (aka 00:00 Pacific, aka 03:00 Eastern)
-    - cron: '0 8 * * *'
+  # schedule:
+  #   # Run nightly at 08:00 UTC (aka 00:00 Pacific, aka 03:00 Eastern)
+  #   - cron: '0 8 * * *'
 
 permissions:
   contents: read # Default everything to read-only
@@ -35,7 +35,7 @@ concurrency:
 
 jobs:
   stage1:
-    if: github.repository_owner == 'llvm'
+    if: github.repository_owner == 'elsteveogrande'
     runs-on: libcxx-self-hosted-linux
     container: ghcr.io/llvm/libcxx-linux-builder:b6bb9dc5abd7c6452c13a53fa8949cb259db459b
     continue-on-error: false
@@ -43,8 +43,8 @@ jobs:
       fail-fast: false
       matrix:
         config: [
-          'frozen-cxx03-headers',
-          'generic-cxx03',
+          # 'frozen-cxx03-headers',
+          # 'generic-cxx03',
           'generic-cxx26',
           'generic-modules'
         ]
@@ -73,7 +73,7 @@ jobs:
             **/CMakeOutput.log
             **/crash_diagnostics/*
   stage2:
-    if: github.repository_owner == 'llvm'
+    if: github.repository_owner == 'elsteveogrande'
     runs-on: libcxx-self-hosted-linux
     container: ghcr.io/llvm/libcxx-linux-builder:b6bb9dc5abd7c6452c13a53fa8949cb259db459b
     needs: [ stage1 ]
@@ -119,7 +119,7 @@ jobs:
             **/CMakeOutput.log
             **/crash_diagnostics/*
   stage3:
-    if: github.repository_owner == 'llvm'
+    if: github.repository_owner == 'elsteveogrande'
     needs: [ stage2 ]
     continue-on-error: false
     strategy:
@@ -238,7 +238,7 @@ jobs:
             **/crash_diagnostics/*
 
   windows:
-    runs-on: windows-2022
+    runs-on: windows-latest
     needs: [ stage2 ]
     strategy:
       fail-fast: false



More information about the llvm-commits mailing list