[libc-commits] [libc] [libc] Fix problem with older compilers that do not have __has_builtin. (PR #150264)

[via libc-commits]

https://github.com/lntue created https://github.com/llvm/llvm-project/pull/150264

Fixing bot failures: https://lab.llvm.org/buildbot/#/builders/10/builds/10025

>From 415c92c83ebe21034ceb13ecfdf8691d6f6e2066 Mon Sep 17 00:00:00 2001
From: Tue Ly <lntue at google.com>
Date: Wed, 23 Jul 2025 12:59:31 -0400
Subject: [PATCH] [libc] Fix problem with older compilers that do not have
 __has_builtin.

---
 libc/src/__support/CPP/type_traits/is_constant_evaluated.h | 4 ++++
 libc/src/__support/macros/attributes.h                     | 6 ++++++
 2 files changed, 10 insertions(+)

diff --git a/libc/src/__support/CPP/type_traits/is_constant_evaluated.h b/libc/src/__support/CPP/type_traits/is_constant_evaluated.h
index 0bb2d0806cb0d..9339af46d6762 100644
--- a/libc/src/__support/CPP/type_traits/is_constant_evaluated.h
+++ b/libc/src/__support/CPP/type_traits/is_constant_evaluated.h
@@ -15,7 +15,11 @@ namespace LIBC_NAMESPACE_DECL {
 namespace cpp {
 
 LIBC_INLINE constexpr bool is_constant_evaluated() {
+#if LIBC_HAS_BUILTIN(__builtin_is_constant_evaluated)
   return __builtin_is_constant_evaluated();
+#else
+  return false;
+#endif
 }
 
 } // namespace cpp
diff --git a/libc/src/__support/macros/attributes.h b/libc/src/__support/macros/attributes.h
index c6474673de85a..62b0f7c3d6155 100644
--- a/libc/src/__support/macros/attributes.h
+++ b/libc/src/__support/macros/attributes.h
@@ -48,4 +48,10 @@
 #define LIBC_PREFERED_TYPE(TYPE)
 #endif
 
+#ifndef __has_builtin
+#define LIBC_HAS_BUILTIN(X) 0
+#else
+#define LIBC_HAS_BUILTIN(X) __has_builtin(X)
+#endif
+
 #endif // LLVM_LIBC_SRC___SUPPORT_MACROS_ATTRIBUTES_H