[libcxx-commits] [libcxx] WIP [libc++][hardening] Overhaul the termination mechanism for hardening (PR #77823)

[Louis Dionne via libcxx-commits]

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+// -*- C++ -*-
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ldionne wrote:

More discussion!

We could actually always use the overriding mechanism but provide our default definition for the assertion handler. That way, the code path for customizing the handler would always be tested, by definition. Something like:

```c++
// in CMakeLists.txt
set(LIBCXX_ASSERTION_HANDLER "libcxx/vendor/llvm/assertion_handler.in" CACHE STR)

// in libcxx/include/__assertion_handler.in
#ifndef _LIBCPP___ASSERTION_HANDLER
#define _LIBCPP___ASSERTION_HANDLER

#include <__availability>
#include <__config>

#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
#  pragma GCC system_header
#endif

copy-paste the contents of @LIBCXX_ASSERTION_HANDLER@ at CMake configuration time

#endif // _LIBCPP___ASSERTION_HANDLER

// in libcxx/vendor/llvm/assertion_handler.in
#if HARDENING_MODE == DEBUG
#   define _LIBCPP_VERBOSE_TRAP(message) ::std::__libcpp_verbose_abort(...)
#else
#   define _LIBCPP_VERBOSE_TRAP(message) ((void)message, __builtin_trap())
#endif
```


https://github.com/llvm/llvm-project/pull/77823