[PATCH] D155064: [clang][SemaCXX] Diagnose tautological uses of consteval if and is_constant_evaluated

[Nikolas Klauser via Phabricator via cfe-commits]

philnik added inline comments.


================
Comment at: libcxx/include/__type_traits/is_constant_evaluated.h:31
+  return false;
+#endif
 }
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Mordante wrote:
> hazohelet wrote:
> > Mordante wrote:
> > > Why is this needed? Does this mean the builtin will fail in C++03 mode?
> > `__libcpp_is_constant_evaluated` always returns false under C++03 or earlier, where constexpr isn't available. This is a fix to run libc++ tests without seeing warnings from clang with this patch.
> > (Live demo: https://godbolt.org/z/oszebM5o5)
> I see can you add a comment in that regard? To me it looks like the builtin fails in C++03, where returning false indeed is always the right answer.
https://godbolt.org/z/bafeeY7b7 shows that `__builtin_is_constant_evaluated()` doesn't always return false in C++03, so this change seems wrong to me.


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  https://reviews.llvm.org/D155064/new/

https://reviews.llvm.org/D155064