[libcxx-commits] [libcxx] [libc++] Make libc++ forward-compatible with AppleClang's definition of __builtin_verbose_trap (PR #99529)

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llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-libcxx

Author: Louis Dionne (ldionne)

<details>
<summary>Changes</summary>

AppleClang as included in the Xcode 16 beta implements __builtin_verbose_trap, but it implements slightly different semantics from the ones implemented upstream. This patch makes libc++ compatible with either definition until we drop support for the version of AppleClang that differs from upstream.

---
Full diff: https://github.com/llvm/llvm-project/pull/99529.diff


1 Files Affected:

- (modified) libcxx/vendor/llvm/default_assertion_handler.in (+7-1) 


``````````diff
diff --git a/libcxx/vendor/llvm/default_assertion_handler.in b/libcxx/vendor/llvm/default_assertion_handler.in
index 9bd831c227798..3b6d6b2cca53c 100644
--- a/libcxx/vendor/llvm/default_assertion_handler.in
+++ b/libcxx/vendor/llvm/default_assertion_handler.in
@@ -24,7 +24,13 @@
 #else
 
 #  if __has_builtin(__builtin_verbose_trap)
-#    define _LIBCPP_ASSERTION_HANDLER(message) __builtin_verbose_trap("libc++", message)
+// AppleClang shipped a slightly different version of __builtin_verbose_trap from the upstream
+// version before upstream Clang actually got the builtin.
+#    if defined(_LIBCPP_APPLE_CLANG_VER) && _LIBCPP_APPLE_CLANG_VER < 17000
+#      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

``````````

</details>


https://github.com/llvm/llvm-project/pull/99529