[libcxx-commits] [libcxx] [libc++] Add std::stacktrace (P0881R7) (PR #136528)

[Jonathan Wakely via libcxx-commits]

================
@@ -0,0 +1,179 @@
+// -*- 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___STACKTRACE_ENTRY_H
+#define _LIBCPP___STACKTRACE_ENTRY_H
+
+#include <__assert>
+#include <__config>
+#include <__functional/function.h>
+#include <__fwd/format.h>
+#include <cstddef>
+#include <cstdint>
+#include <cstring>
+#include <string>
+#include <string_view>
+#if _LIBCPP_HAS_LOCALIZATION
+#  include <__fwd/ostream.h>
+#endif // _LIBCPP_HAS_LOCALIZATION
+
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
+#  pragma GCC system_header
+#endif
+
+_LIBCPP_PUSH_MACROS
+#include <__undef_macros>
+
+#if _LIBCPP_STD_VER >= 23 && _LIBCPP_AVAILABILITY_HAS_STACKTRACE
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+class stacktrace_entry;
+
+namespace __stacktrace {
+
+struct _Image;
+
+struct _StringWrapper {
+  // XXX FIXME TODO:
+  // Figure out a solution for creating strings while respecting
+  // the caller's allocator they provided:
+  //   1. properly typeerase basic_strings' allocator types
+  //   2. move all code into headers (seems like a bad idea)
+  //   3. leave these as oversized char arrays, seems suboptimal
+  //   4. just use std::string, which is just plain wrong
+  //   5. ...?
+
+  std::string __str_;
+
+  _LIBCPP_HIDE_FROM_ABI std::string_view view() const { return __str_; }
+
+  _LIBCPP_HIDE_FROM_ABI _StringWrapper& assign(std::string_view __view) {
+    __str_ = __view;
+    return *this;
+  }
+};
+
+struct _Entry {
+#  if defined(PATH_MAX)
+  constexpr static size_t __max_file_len = PATH_MAX;
+#  elif defined(MAX_PATH)
+  constexpr static size_t __max_file_len = MAX_PATH;
+#  else
+  constexpr static size_t __max_file_len = (1 << 10);
+#  endif
+
+  uintptr_t __addr_{};
+  _StringWrapper __desc_{};
+  _StringWrapper __file_{};
+  uint_least32_t __line_{};
+  _Image const* __image_{};
+
+#  if _LIBCPP_HAS_LOCALIZATION
+  _LIBCPP_EXPORTED_FROM_ABI std::ostream& write_to(std::ostream& __os) const;
+  _LIBCPP_EXPORTED_FROM_ABI string to_string() const;
+#  endif // _LIBCPP_HAS_LOCALIZATION
+
+  _LIBCPP_EXPORTED_FROM_ABI size_t hash() const;
+  _LIBCPP_HIDE_FROM_ABI static _Entry& base(stacktrace_entry& __entry);
+  _LIBCPP_HIDE_FROM_ABI static _Entry const& base(stacktrace_entry const& __entry);
+
+  _LIBCPP_HIDE_FROM_ABI uintptr_t adjusted_addr() const;
+
+  _LIBCPP_HIDE_FROM_ABI ~_Entry()                                  = default;
+  _LIBCPP_HIDE_FROM_ABI constexpr _Entry()                         = default;
+  _LIBCPP_HIDE_FROM_ABI constexpr _Entry(const _Entry&)            = default;
+  _LIBCPP_HIDE_FROM_ABI constexpr _Entry& operator=(const _Entry&) = default;
+  _LIBCPP_HIDE_FROM_ABI constexpr _Entry(_Entry&&)                 = default;
+  _LIBCPP_HIDE_FROM_ABI constexpr _Entry& operator=(_Entry&&)      = default;
+};
+
+struct _Trace;
+
+} // namespace __stacktrace
+
+class stacktrace_entry {
+  _LIBCPP_HIDE_FROM_ABI friend struct __stacktrace::_Entry;
+  __stacktrace::_Entry __base_{};
+
+public:
+  // (19.6.3.1) Overview [stacktrace.entry.overview]
+  using native_handle_type = uintptr_t;
+
+  // (19.6.3.2) [stacktrace.entry.cons], constructors
+  _LIBCPP_HIDE_FROM_ABI ~stacktrace_entry() noexcept                                            = default;
+  _LIBCPP_HIDE_FROM_ABI constexpr stacktrace_entry() noexcept                                   = default;
+  _LIBCPP_HIDE_FROM_ABI constexpr stacktrace_entry(const stacktrace_entry&) noexcept            = default;
+  _LIBCPP_HIDE_FROM_ABI constexpr stacktrace_entry& operator=(const stacktrace_entry&) noexcept = default;
+
+  // (19.6.3.3) [stacktrace.entry.obs], observers
+  _LIBCPP_HIDE_FROM_ABI constexpr native_handle_type native_handle() const noexcept { return __base_.__addr_; }
+  _LIBCPP_HIDE_FROM_ABI constexpr explicit operator bool() const noexcept { return native_handle() != 0; }
+
+  // (19.6.3.4) [stacktrace.entry.query], query
+  _LIBCPP_HIDE_FROM_ABI string description() const { return string(__base_.__desc_.view()); }
+  _LIBCPP_HIDE_FROM_ABI string source_file() const { return string(__base_.__file_.view()); }
+  _LIBCPP_HIDE_FROM_ABI uint_least32_t source_line() const { return __base_.__line_; }
+
+  // (19.6.3.5) [stacktrace.entry.cmp], comparison
+  _LIBCPP_HIDE_FROM_ABI friend constexpr bool
+  operator==(const stacktrace_entry& __x, const stacktrace_entry& __y) noexcept {
+    return __x.native_handle() == __y.native_handle();
+  }
+
+  _LIBCPP_HIDE_FROM_ABI friend constexpr strong_ordering
+  operator<=>(const stacktrace_entry& __x, const stacktrace_entry& __y) noexcept {
+    return __x.native_handle() <=> __y.native_handle();
+  }
+};
+
+// (19.6.4.6)
+// Non-member functions [stacktrace.basic.nonmem]
+
+#  if _LIBCPP_HAS_LOCALIZATION
+
+_LIBCPP_HIDE_FROM_ABI inline string to_string(const std::stacktrace_entry& __entry) {
+  return __stacktrace::_Entry::base(__entry).to_string();
+}
+
+_LIBCPP_HIDE_FROM_ABI inline ostream& operator<<(ostream& __os, const stacktrace_entry& __entry) {
+  return __stacktrace::_Entry::base(__entry).write_to(__os);
----------------
jwakely wrote:

The `write_to` function uses `std::hex` and `std::setfill` and doesn't restore them, which alters the state of `__os` here. That `write_to` behaviour is fine for `to_string` where it writes to a local stringstream (which could be ostringstream but nevermind) but not for `operator<<` on arbitrary user-provided streams, e.g. std::cout.

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