From add16a8da9ccd07eabda2dffd0d32188f07da09c Mon Sep 17 00:00:00 2001 From: Eric Fiselier Date: Wed, 24 Apr 2019 02:23:30 +0000 Subject: [Builtins] Implement __builtin_is_constant_evaluated for use in C++2a Summary: This patch implements `__builtin_is_constant_evaluated` as specifier by [P0595R2](https://wg21.link/p0595r2). It is built on the back of Bill Wendling's work for `__builtin_constant_p()`. More tests to come, but early feedback is appreciated. I plan to implement warnings for common mis-usages like those belowe in a following patch: ``` void foo(int x) { if constexpr (std::is_constant_evaluated())) { // condition is always `true`. Should use plain `if` instead. foo_constexpr(x); } else { foo_runtime(x); } } ``` Reviewers: rsmith, MaskRay, bruno, void Reviewed By: rsmith Subscribers: dexonsmith, zoecarver, fdeazeve, kristina, cfe-commits Differential Revision: https://reviews.llvm.org/D55500 llvm-svn: 359067 --- clang/test/Sema/builtins.c | 6 ++++++ 1 file changed, 6 insertions(+) (limited to 'clang/test/Sema/builtins.c') diff --git a/clang/test/Sema/builtins.c b/clang/test/Sema/builtins.c index 052832bcf4f..1d41bcf9f08 100644 --- a/clang/test/Sema/builtins.c +++ b/clang/test/Sema/builtins.c @@ -314,3 +314,9 @@ void test23() { memcpy(buf, src, 11); // expected-warning{{'memcpy' will always overflow; destination buffer has size 10, but size argument is 11}} my_memcpy(buf, src, 11); // expected-warning{{'memcpy' will always overflow; destination buffer has size 10, but size argument is 11}} } + +// Test that __builtin_is_constant_evaluated() is not allowed in C +int test_cxx_builtin() { + // expected-error@+1 {{use of unknown builtin '__builtin_is_constant_evaluated'}} + return __builtin_is_constant_evaluated(); +} -- cgit v1.2.3