[libc++][hardening][NFC] Introduce _LIBCPP_VERBOSE_TRAP macro.
#148262
Conversation
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
llvmbot
added
the
libc++
|
@llvm/pr-subscribers-libcxx Author: Konstantin Varlamov (var-const) ChangesSplit out the calls to Full diff: https://github.com/llvm/llvm-project/pull/148262.diff 3 Files Affected:
diff --git a/libcxx/include/CMakeLists.txt b/libcxx/include/CMakeLists.txt
index c8e6d28584623..f79edc9e32599 100644
--- a/libcxx/include/CMakeLists.txt
+++ b/libcxx/include/CMakeLists.txt
@@ -944,6 +944,7 @@ set(files
__vector/vector_bool.h
__vector/vector_bool_formatter.h
__verbose_abort
+ __verbose_trap
algorithm
any
array
diff --git a/libcxx/include/__verbose_trap b/libcxx/include/__verbose_trap
new file mode 100644
index 0000000000000..db77b29e69062
--- /dev/null
+++ b/libcxx/include/__verbose_trap
@@ -0,0 +1,37 @@
+// -*- 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___VERBOSE_TRAP
+#define _LIBCPP___VERBOSE_TRAP
+
+#include <__config>
+
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
+# pragma GCC system_header
+#endif
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+# if __has_builtin(__builtin_verbose_trap)
+// AppleClang shipped a slightly different version of __builtin_verbose_trap from the upstream
+// version before upstream Clang actually got the builtin.
+// TODO: Remove once AppleClang supports the two-arguments version of the builtin.
+# if defined(_LIBCPP_APPLE_CLANG_VER) && _LIBCPP_APPLE_CLANG_VER < 1700
+# define _LIBCPP_VERBOSE_TRAP(message) __builtin_verbose_trap(message)
+# else
+# define _LIBCPP_VERBOSE_TRAP(message) __builtin_verbose_trap("libc++", message)
+# endif
+# else
+# define _LIBCPP_VERBOSE_TRAP(message) ((void)message, __builtin_trap())
+# endif
+
+
+_LIBCPP_END_NAMESPACE_STD
+
+#endif // _LIBCPP___VERBOSE_TRAP
diff --git a/libcxx/vendor/llvm/default_assertion_handler.in b/libcxx/vendor/llvm/default_assertion_handler.in
index 1d6b21fc6bb45..90b202a2dae57 100644
--- a/libcxx/vendor/llvm/default_assertion_handler.in
+++ b/libcxx/vendor/llvm/default_assertion_handler.in
@@ -15,6 +15,7 @@
# include <__cxx03/__verbose_abort>
#else
# include <__config>
+# include <__verbose_trap>
# include <__verbose_abort>
#endif
@@ -28,18 +29,7 @@
#else
-# if __has_builtin(__builtin_verbose_trap)
-// AppleClang shipped a slightly different version of __builtin_verbose_trap from the upstream
-// version before upstream Clang actually got the builtin.
-// TODO: Remove once AppleClang supports the two-arguments version of the builtin.
-# if defined(_LIBCPP_APPLE_CLANG_VER) && _LIBCPP_APPLE_CLANG_VER < 1700
-# define _LIBCPP_ASSERTION_HANDLER(message) __builtin_verbose_trap(message)
-# else
-# define _LIBCPP_ASSERTION_HANDLER(message) __builtin_verbose_trap("libc++", message)
-# endif
-# else
-# define _LIBCPP_ASSERTION_HANDLER(message) ((void)message, __builtin_trap())
-# endif
+# define _LIBCPP_ASSERTION_HANDLER(message) _LIBCPP_VERBOSE_TRAP(message)
#endif // _LIBCPP_HARDENING_MODE == _LIBCPP_HARDENING_MODE_DEBUG
|
var-const
commented
Jul 11, 2025
There was a problem hiding this comment.
Question: what do we do about the frozen headers?
There was a problem hiding this comment.
This is a good question, and actually it's not easy to answer IMO. CCing @philnik777 .
I see a few options:
- Introduce
<__cxx03/__verbose_trap>. This seems to go against the notion of having "frozen headers". - Define
_LIBCPP_VERBOSE_TRAPinline insidedefault_assertion_handler.ininside this#ifblock. This is equivalent to (1) except we don't introduce a new header under__cxx03. - Always use the non-C++03 headers from
default_assertion_handler.in. So this means get rid of the#ifand always include<__config>and<__verbose_abort>, never their<__cxx03/...>counterparts. This would be doable since<__verbose_abort>doesn't actually need C++11, but it goes against the principle of the split and may cause other conflicts if we somehow end up including both<__config>and<__cxx03/__config>. - Have two copies of
default_assertion_handler.in, one normal and one for the frozen headers. This is a bit tricky sincedefault_assertion_handler.inis something we set up from CMake and expect vendors to be able to override.
I think (1) is the best outcome here. We'll have to support these hardening improvements in frozen-C++03 anyways otherwise this'll be a regression in functionality.
There was a problem hiding this comment.
Thanks for the comprehensive overview of alternatives, this is super useful!
From what I gather, the frozen headers are still undergoing development, so them being completely frozen is the end goal rather than a description of the current state. If that perspective is valid, I also think that option (1) is the best, or at least the lesser evil out of the available options.
|
✅ With the latest revision this PR passed the C/C++ code formatter. |
Split out the calls to `__builtin_verbose_trap` into a separate header. This is just a refactoring to make the code a bit more structured.
var-const
force-pushed
the
varconst/hardening-semantics-split-verbose_trap
branch
from
42bbe5d to
6708ebf
Compare
ldionne
reviewed
Jul 11, 2025
There was a problem hiding this comment.
This is a good question, and actually it's not easy to answer IMO. CCing @philnik777 .
I see a few options:
- Introduce
<__cxx03/__verbose_trap>. This seems to go against the notion of having "frozen headers". - Define
_LIBCPP_VERBOSE_TRAPinline insidedefault_assertion_handler.ininside this#ifblock. This is equivalent to (1) except we don't introduce a new header under__cxx03. - Always use the non-C++03 headers from
default_assertion_handler.in. So this means get rid of the#ifand always include<__config>and<__verbose_abort>, never their<__cxx03/...>counterparts. This would be doable since<__verbose_abort>doesn't actually need C++11, but it goes against the principle of the split and may cause other conflicts if we somehow end up including both<__config>and<__cxx03/__config>. - Have two copies of
default_assertion_handler.in, one normal and one for the frozen headers. This is a bit tricky sincedefault_assertion_handler.inis something we set up from CMake and expect vendors to be able to override.
I think (1) is the best outcome here. We'll have to support these hardening improvements in frozen-C++03 anyways otherwise this'll be a regression in functionality.
ldionne
approved these changes
Jul 14, 2025
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
3 participants
Add this suggestion to a batch that can be applied as a single commit.
This suggestion is invalid because no changes were made to the code.
Suggestions cannot be applied while the pull request is closed.
Suggestions cannot be applied while viewing a subset of changes.
Only one suggestion per line can be applied in a batch.
Add this suggestion to a batch that can be applied as a single commit.
Applying suggestions on deleted lines is not supported.
You must change the existing code in this line in order to create a valid suggestion.
Outdated suggestions cannot be applied.
This suggestion has been applied or marked resolved.
Suggestions cannot be applied from pending reviews.
Suggestions cannot be applied on multi-line comments.
Suggestions cannot be applied while the pull request is queued to merge.
Suggestion cannot be applied right now. Please check back later.
Split out the calls to
__builtin_verbose_trapinto a separate header.This is just a refactoring to make the code a bit more structured.