[libcxx-commits] [libcxx] [libc++][hardening] Always enable all checks during constant evaluation (PR #107713)

[Mital Ashok via libcxx-commits]

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@@ -17,23 +17,38 @@
 #  pragma GCC system_header
 #endif
 
+#ifdef _LIBCPP_COMPILER_CLANG_BASED
+// TODO: use `_LIBCPP_DIAGNOSTIC_*` macros after #107715 is fixed in all supported clang compilers
+#  define _LIBCPP_ASSERT_IS_CONSTANT_EVALUATED                                                                         \
+    (_Pragma("clang diagnostic push") _Pragma("clang diagnostic ignored \"-Wconstant-evaluated\"")                     \
+         __builtin_is_constant_evaluated() _Pragma("clang diagnostic pop"))
+#else
+#  define _LIBCPP_ASSERT_IS_CONSTANT_EVALUATED (__builtin_is_constant_evaluated())
+#endif
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MitalAshok wrote:

This would be diagnosed if used in a manifestly constant evaluated context. This is mainly in an `if consteval` branch or `consteval` function. No `if consteval` currently exists in libc++ and no `consteval` libc++ functions contain any assertions, but in the future they might.

Also more exotic cases, like when the assertion is directly in a constinit initialiser, array bound or static_assert, like in the added test. But these will never happen in real libc++ code.


https://github.com/llvm/llvm-project/pull/107713