[clang] [clang] Migrate DR tests to `static_assert` (PR #88611)

[Vlad Serebrennikov via cfe-commits]

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@@ -5,6 +5,17 @@
 // RUN: %clang_cc1 -std=c++11 -verify=expected,cxx98-14,cxx98-17,cxx98-20,cxx11-14,since-cxx11 -triple %itanium_abi_triple %s -fexceptions -fcxx-exceptions -pedantic-errors
 // RUN: %clang_cc1 -std=c++98 -verify=expected,cxx98-14,cxx98-17,cxx98-20,cxx98 -triple %itanium_abi_triple %s -fexceptions -fcxx-exceptions -pedantic-errors
 
+#if __cplusplus == 199711L
+#define static_assert(...) __extension__ _Static_assert(__VA_ARGS__)
+// cxx98-error at -1 {{variadic macros are a C99 feature}}
+#endif
+
+#if __cplusplus == 199711L
+#define __enable_constant_folding(x) (__builtin_constant_p(x) ? (x) : (x))
+#else
+#define __enable_constant_folding
+#endif
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Endilll wrote:

You're correct that having a very thin standard/backporting library would be beneficial. There have been efforts last year to improve testing infrastructure, and this particular detail was a part of the plan, but those efforts have been stalled for months. I'd keep things as-is until the time comes.

I've put up an RFC a year ago if you're interested in a context: https://discourse.llvm.org/t/rfc-opt-in-way-to-make-verifydiagnosticconsumer-slightly-less-strict/70747

https://github.com/llvm/llvm-project/pull/88611