[libcxx-commits] [libcxx] [libc++][hardening] Introduce a dylib function to log hardening errors. (PR #148266)

Konstantin Varlamov via libcxx-commits libcxx-commits at lists.llvm.org
Sat Jul 12 01:58:59 PDT 2025


https://github.com/var-const updated https://github.com/llvm/llvm-project/pull/148266

>From 1fcfec368e34964811270b9a10ad969814e3a691 Mon Sep 17 00:00:00 2001
From: Konstantin Varlamov <varconst at apple.com>
Date: Fri, 11 Jul 2025 10:29:10 -0700
Subject: [PATCH 1/2] [libc++][hardening] Introduce a dylib function to log
 hardening errors.

Unlike `verbose_abort`, this function merely logs the error but does not
terminate execution. It is intended to make it possible to implement the
`observe` semantic for Hardening.
---
 libcxx/include/CMakeLists.txt                 |  1 +
 libcxx/include/__configuration/availability.h |  5 ++
 libcxx/include/__log_hardening_failure        | 45 +++++++++++++++++
 libcxx/src/CMakeLists.txt                     |  1 +
 libcxx/src/log_hardening_failure.cpp          | 49 +++++++++++++++++++
 5 files changed, 101 insertions(+)
 create mode 100644 libcxx/include/__log_hardening_failure
 create mode 100644 libcxx/src/log_hardening_failure.cpp

diff --git a/libcxx/include/CMakeLists.txt b/libcxx/include/CMakeLists.txt
index c8e6d28584623..2f8be540e73e2 100644
--- a/libcxx/include/CMakeLists.txt
+++ b/libcxx/include/CMakeLists.txt
@@ -535,6 +535,7 @@ set(files
   __locale_dir/time.h
   __locale_dir/wbuffer_convert.h
   __locale_dir/wstring_convert.h
+  __log_hardening_failure
   __math/abs.h
   __math/copysign.h
   __math/error_functions.h
diff --git a/libcxx/include/__configuration/availability.h b/libcxx/include/__configuration/availability.h
index ae58e36b508b4..cb72e927caa9c 100644
--- a/libcxx/include/__configuration/availability.h
+++ b/libcxx/include/__configuration/availability.h
@@ -304,6 +304,11 @@
 #define _LIBCPP_AVAILABILITY_HAS_VERBOSE_ABORT _LIBCPP_INTRODUCED_IN_LLVM_15
 #define _LIBCPP_AVAILABILITY_VERBOSE_ABORT _LIBCPP_INTRODUCED_IN_LLVM_15_ATTRIBUTE
 
+// This controls whether the library provides a function to log hardening failures without terminating the program (for
+// the `observe` assertion semantic).
+#define _LIBCPP_AVAILABILITY_HAS_LOG_HARDENING_FAILURE _LIBCPP_INTRODUCED_IN_LLVM_21
+#define _LIBCPP_AVAILABILITY_LOG_HARDENING_FAILURE _LIBCPP_INTRODUCED_IN_LLVM_21_ATTRIBUTE
+
 // This controls the availability of the C++17 std::pmr library,
 // which is implemented in large part in the built library.
 //
diff --git a/libcxx/include/__log_hardening_failure b/libcxx/include/__log_hardening_failure
new file mode 100644
index 0000000000000..73cff0ac64155
--- /dev/null
+++ b/libcxx/include/__log_hardening_failure
@@ -0,0 +1,45 @@
+// -*- 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___LOG_HARDENING_FAILURE
+#define _LIBCPP___LOG_HARDENING_FAILURE
+
+#include <__config>
+
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
+#  pragma GCC system_header
+#endif
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+// This function should never be called directly from the code -- it should only be called through the
+// `_LIBCPP_LOG_HARDENING_FAILURE` macro.
+_LIBCPP_AVAILABILITY_LOG_HARDENING_FAILURE _LIBCPP_OVERRIDABLE_FUNC_VIS void
+__libcpp_log_hardening_failure(const char* message) _NOEXCEPT;
+
+// _LIBCPP_LOG_HARDENING_FAILURE(message)
+//
+// This macro is used to log a hardening failure without terminating the program (as is the case if the `observe`
+// assertion semantic is used). Where possible, it logs in a way that indicates a fatal error (which might include
+// capturing the stack trace).
+#if !defined(_LIBCPP_LOG_HARDENING_FAILURE)
+
+#  if !_LIBCPP_AVAILABILITY_HAS_LOG_HARDENING_FAILURE
+// The decltype is there to suppress -Wunused warnings in this configuration.
+void __use(const char*);
+#    define _LIBCPP_LOG_HARDENING_FAILURE(message) (decltype(::std::__use(message))())
+#  else
+#    define _LIBCPP_LOG_HARDENING_FAILURE(message) ::std::__libcpp_log_hardening_failure(message)
+#  endif
+
+#endif // !defined(_LIBCPP_LOG_HARDENING_FAILURE)
+
+_LIBCPP_END_NAMESPACE_STD
+
+#endif // _LIBCPP___LOG_HARDENING_FAILURE
diff --git a/libcxx/src/CMakeLists.txt b/libcxx/src/CMakeLists.txt
index 97fe57a5f24f8..926deb3a1c732 100644
--- a/libcxx/src/CMakeLists.txt
+++ b/libcxx/src/CMakeLists.txt
@@ -30,6 +30,7 @@ set(LIBCXX_SOURCES
   include/ryu/ryu.h
   include/to_chars_floating_point.h
   include/from_chars_floating_point.h
+  log_hardening_failure.cpp
   memory.cpp
   memory_resource.cpp
   new_handler.cpp
diff --git a/libcxx/src/log_hardening_failure.cpp b/libcxx/src/log_hardening_failure.cpp
new file mode 100644
index 0000000000000..7e408a6f010b4
--- /dev/null
+++ b/libcxx/src/log_hardening_failure.cpp
@@ -0,0 +1,49 @@
+//===----------------------------------------------------------------------===//
+//
+// 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 <__log_hardening_failure>
+#include <cstdio>
+
+#ifdef __BIONIC__
+#  include <syslog.h>
+extern "C" void android_set_abort_message(const char* msg);
+#endif // __BIONIC__
+
+#if defined(__APPLE__) && __has_include(<os/reason_private.h>)
+#  include <os/reason_private.h>
+#endif
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+_LIBCPP_WEAK void __libcpp_log_hardening_failure(const char* message) noexcept {
+  // On Apple platforms, use the `os_fault_with_payload` OS function that simulates a crash.
+#if defined(__APPLE__) && __has_include(<os/reason_private.h>)
+  os_fault_with_payload(
+      /*reason_namespace=*/OS_REASON_SECURITY,
+      /*reason_code=*/0,
+      /*payload=*/nullptr,
+      /*payload_size=*/0,
+      /*reason_string=*/message,
+      /*reason_flags=*/0);
+
+#elif defined(__BIONIC__)
+  // Show error in tombstone.
+  android_set_abort_message(message);
+
+  // Show error in logcat.
+  openlog("libc++", 0, 0);
+  syslog(LOG_CRIT, "%s", message);
+  closelog();
+
+#else
+  fprintf(stderr, "%s", message);
+#endif
+}
+
+_LIBCPP_END_NAMESPACE_STD

>From ef34aded6cfa935fe9d904bb8d4f79bfb705137a Mon Sep 17 00:00:00 2001
From: Konstantin Varlamov <varconst at apple.com>
Date: Sat, 12 Jul 2025 01:58:15 -0700
Subject: [PATCH 2/2] Address feedback

---
 libcxx/include/CMakeLists.txt                 |  2 +-
 libcxx/include/__configuration/availability.h |  8 +--
 libcxx/include/__log_error                    | 50 +++++++++++++++++++
 libcxx/include/__log_hardening_failure        | 45 -----------------
 libcxx/include/module.modulemap.in            |  3 ++
 libcxx/src/CMakeLists.txt                     |  2 +-
 ...og_hardening_failure.cpp => log_error.cpp} | 16 +++++-
 7 files changed, 73 insertions(+), 53 deletions(-)
 create mode 100644 libcxx/include/__log_error
 delete mode 100644 libcxx/include/__log_hardening_failure
 rename libcxx/src/{log_hardening_failure.cpp => log_error.cpp} (81%)

diff --git a/libcxx/include/CMakeLists.txt b/libcxx/include/CMakeLists.txt
index 2f8be540e73e2..ceaf45e9e8ae6 100644
--- a/libcxx/include/CMakeLists.txt
+++ b/libcxx/include/CMakeLists.txt
@@ -535,7 +535,7 @@ set(files
   __locale_dir/time.h
   __locale_dir/wbuffer_convert.h
   __locale_dir/wstring_convert.h
-  __log_hardening_failure
+  __log_error
   __math/abs.h
   __math/copysign.h
   __math/error_functions.h
diff --git a/libcxx/include/__configuration/availability.h b/libcxx/include/__configuration/availability.h
index cb72e927caa9c..5de0b98ba22a9 100644
--- a/libcxx/include/__configuration/availability.h
+++ b/libcxx/include/__configuration/availability.h
@@ -304,10 +304,10 @@
 #define _LIBCPP_AVAILABILITY_HAS_VERBOSE_ABORT _LIBCPP_INTRODUCED_IN_LLVM_15
 #define _LIBCPP_AVAILABILITY_VERBOSE_ABORT _LIBCPP_INTRODUCED_IN_LLVM_15_ATTRIBUTE
 
-// This controls whether the library provides a function to log hardening failures without terminating the program (for
-// the `observe` assertion semantic).
-#define _LIBCPP_AVAILABILITY_HAS_LOG_HARDENING_FAILURE _LIBCPP_INTRODUCED_IN_LLVM_21
-#define _LIBCPP_AVAILABILITY_LOG_HARDENING_FAILURE _LIBCPP_INTRODUCED_IN_LLVM_21_ATTRIBUTE
+// This controls whether the library provides a function to log errors without terminating the program (used in
+// particular by the `observe` assertion semantic).
+#define _LIBCPP_AVAILABILITY_HAS_LOG_ERROR _LIBCPP_INTRODUCED_IN_LLVM_21
+#define _LIBCPP_AVAILABILITY_LOG_ERROR _LIBCPP_INTRODUCED_IN_LLVM_21_ATTRIBUTE
 
 // This controls the availability of the C++17 std::pmr library,
 // which is implemented in large part in the built library.
diff --git a/libcxx/include/__log_error b/libcxx/include/__log_error
new file mode 100644
index 0000000000000..9f308898247c4
--- /dev/null
+++ b/libcxx/include/__log_error
@@ -0,0 +1,50 @@
+// -*- 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___LOG_ERROR
+#define _LIBCPP___LOG_ERROR
+
+#include <__config>
+
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
+#  pragma GCC system_header
+#endif
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+enum class _LogErrorReason {
+  // Where possible, it logs in a way that indicates a fatal error (which might include capturing the stack trace).
+  _HardeningFailure
+};
+
+// This function should never be called directly from the code -- it should only be called through the
+// `_LIBCPP_LOG_ERROR` macro.
+_LIBCPP_AVAILABILITY_LOG_ERROR _LIBCPP_EXPORTED_FROM_ABI void
+__log_error(_LogErrorReason __reason, const char* __message) _NOEXCEPT;
+
+// _LIBCPP_LOG_ERROR(message)
+//
+// This macro is used to log an error without terminating the program (as is the case for hardening failures if the
+// `observe` assertion semantic is used, for example).
+
+#if !defined(_LIBCPP_LOG_ERROR)
+
+#  if !_LIBCPP_AVAILABILITY_HAS_LOG_ERROR
+// The decltype is there to suppress -Wunused warnings in this configuration.
+void __use(const char*);
+#    define _LIBCPP_LOG_ERROR(__message) (decltype(::std::__use(__message))())
+#  else
+#    define _LIBCPP_LOG_ERROR(__reason, __message) ::std::__log_error(__reason, __message)
+#  endif
+
+#endif // !defined(_LIBCPP_LOG_ERROR)
+
+_LIBCPP_END_NAMESPACE_STD
+
+#endif // _LIBCPP___LOG_ERROR
diff --git a/libcxx/include/__log_hardening_failure b/libcxx/include/__log_hardening_failure
deleted file mode 100644
index 73cff0ac64155..0000000000000
--- a/libcxx/include/__log_hardening_failure
+++ /dev/null
@@ -1,45 +0,0 @@
-// -*- 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___LOG_HARDENING_FAILURE
-#define _LIBCPP___LOG_HARDENING_FAILURE
-
-#include <__config>
-
-#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
-#  pragma GCC system_header
-#endif
-
-_LIBCPP_BEGIN_NAMESPACE_STD
-
-// This function should never be called directly from the code -- it should only be called through the
-// `_LIBCPP_LOG_HARDENING_FAILURE` macro.
-_LIBCPP_AVAILABILITY_LOG_HARDENING_FAILURE _LIBCPP_OVERRIDABLE_FUNC_VIS void
-__libcpp_log_hardening_failure(const char* message) _NOEXCEPT;
-
-// _LIBCPP_LOG_HARDENING_FAILURE(message)
-//
-// This macro is used to log a hardening failure without terminating the program (as is the case if the `observe`
-// assertion semantic is used). Where possible, it logs in a way that indicates a fatal error (which might include
-// capturing the stack trace).
-#if !defined(_LIBCPP_LOG_HARDENING_FAILURE)
-
-#  if !_LIBCPP_AVAILABILITY_HAS_LOG_HARDENING_FAILURE
-// The decltype is there to suppress -Wunused warnings in this configuration.
-void __use(const char*);
-#    define _LIBCPP_LOG_HARDENING_FAILURE(message) (decltype(::std::__use(message))())
-#  else
-#    define _LIBCPP_LOG_HARDENING_FAILURE(message) ::std::__libcpp_log_hardening_failure(message)
-#  endif
-
-#endif // !defined(_LIBCPP_LOG_HARDENING_FAILURE)
-
-_LIBCPP_END_NAMESPACE_STD
-
-#endif // _LIBCPP___LOG_HARDENING_FAILURE
diff --git a/libcxx/include/module.modulemap.in b/libcxx/include/module.modulemap.in
index 45b9c72a05b82..763d32296a03d 100644
--- a/libcxx/include/module.modulemap.in
+++ b/libcxx/include/module.modulemap.in
@@ -2353,6 +2353,9 @@ module std [system] {
     header "__std_mbstate_t.h"
     export *
   }
+  module log_error {
+    header "__log_error"
+  }
   module verbose_abort {
     header "__verbose_abort"
   }
diff --git a/libcxx/src/CMakeLists.txt b/libcxx/src/CMakeLists.txt
index 926deb3a1c732..0e83b2728aa5a 100644
--- a/libcxx/src/CMakeLists.txt
+++ b/libcxx/src/CMakeLists.txt
@@ -30,7 +30,7 @@ set(LIBCXX_SOURCES
   include/ryu/ryu.h
   include/to_chars_floating_point.h
   include/from_chars_floating_point.h
-  log_hardening_failure.cpp
+  log_error.cpp
   memory.cpp
   memory_resource.cpp
   new_handler.cpp
diff --git a/libcxx/src/log_hardening_failure.cpp b/libcxx/src/log_error.cpp
similarity index 81%
rename from libcxx/src/log_hardening_failure.cpp
rename to libcxx/src/log_error.cpp
index 7e408a6f010b4..01ddaf65bf618 100644
--- a/libcxx/src/log_hardening_failure.cpp
+++ b/libcxx/src/log_error.cpp
@@ -7,7 +7,7 @@
 //===----------------------------------------------------------------------===//
 
 #include <__config>
-#include <__log_hardening_failure>
+#include <__log_error>
 #include <cstdio>
 
 #ifdef __BIONIC__
@@ -21,7 +21,9 @@ extern "C" void android_set_abort_message(const char* msg);
 
 _LIBCPP_BEGIN_NAMESPACE_STD
 
-_LIBCPP_WEAK void __libcpp_log_hardening_failure(const char* message) noexcept {
+namespace {
+
+void log_fatal_error(const char* message) noexcept {
   // On Apple platforms, use the `os_fault_with_payload` OS function that simulates a crash.
 #if defined(__APPLE__) && __has_include(<os/reason_private.h>)
   os_fault_with_payload(
@@ -46,4 +48,14 @@ _LIBCPP_WEAK void __libcpp_log_hardening_failure(const char* message) noexcept {
 #endif
 }
 
+} // namespace
+
+void __log_error(_LogErrorReason reason, const char* message) noexcept {
+  switch (reason) {
+  case _LogErrorReason::_HardeningFailure:
+  default:
+    log_fatal_error(message);
+  }
+}
+
 _LIBCPP_END_NAMESPACE_STD



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