release/18.x: [Headers] Don't declare unreachable() from stddef.h in C++ (#86748) #87696
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@AaronBallman What do you think about merging this PR to the release branch? |
llvmbot
added
clang
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@llvm/pr-subscribers-backend-x86 @llvm/pr-subscribers-clang Author: None (llvmbot) ChangesBackport df69a30 Requested by: @ian-twilightcoder Full diff: https://github.com/llvm/llvm-project/pull/87696.diff 1 Files Affected:
diff --git a/clang/lib/Headers/__stddef_unreachable.h b/clang/lib/Headers/__stddef_unreachable.h
index 518580c92d3f5d..61df43e9732f8a 100644
--- a/clang/lib/Headers/__stddef_unreachable.h
+++ b/clang/lib/Headers/__stddef_unreachable.h
@@ -7,6 +7,8 @@
*===-----------------------------------------------------------------------===
*/
+#ifndef __cplusplus
+
/*
* When -fbuiltin-headers-in-system-modules is set this is a non-modular header
* and needs to behave as if it was textual.
@@ -15,3 +17,5 @@
(__has_feature(modules) && !__building_module(_Builtin_stddef))
#define unreachable() __builtin_unreachable()
#endif
+
+#endif
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Nominating for backport because this is a C++ regression that was caused by https://reviews.llvm.org/D157757 |
AaronBallman
approved these changes
Apr 5, 2024
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@tstellar is there anything else I need to do for this one? |
Even if __need_unreachable is set, stddef.h should not declare unreachable() in C++ because it conflicts with the declaration in \<utility>. (cherry picked from commit df69a30)
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Hi @ian-twilightcoder (or anyone else). If you would like to add a note about this fix in the release notes (completely optional). Please reply to this comment with a one or two sentence description of the fix. |
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I don't think we need to release note this one, it's just restoring LLVM 17 behavior. |
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Backport df69a30
Requested by: @ian-twilightcoder