From 2de6675b66388341ba9d71bcaa47c47e87f667b9 Mon Sep 17 00:00:00 2001 From: Thomas Munro Date: Wed, 11 Mar 2026 13:26:22 +1300 Subject: [PATCH v2 02/19] Provide pg_has_builtin() macro. The traditional approach of configure/meson problems that define HAVE__BUILTIN_FOO doesn't work for results that vary across the CC, CXX and CLANG compilers. In Clang since early version, and in GCC 10+, you can test with __has_builtin(__builtin_foo) instead. This wrapper can be tested in preprocessor conditions using pg_has_builtin(__builtin_foo). This approach has a bootstrapping problem, since __has_builtin() itself was adopted only ~6 years ago by GCC, so it will always evaluate to false for older GCC versions. Traditional configure probes therefore remain useful for well established builtins where the three selected compilers are unlikely to differ. This macro is useful for builtins that were more recently invented, or adopted late by one or the other of GCC and Clang. --- src/include/c.h | 10 ++++++++++ 1 file changed, 10 insertions(+) diff --git a/src/include/c.h b/src/include/c.h index 5b678283469..5c74da5004e 100644 --- a/src/include/c.h +++ b/src/include/c.h @@ -116,6 +116,16 @@ extern "C++" #define inline #endif +/* + * Clang and GCC 10+ can test for a builtin's presence. This can be useful + * for builtins that might be present for CC but not CXX or CLANG. + */ +#ifdef __has_builtin +#define pg_has_builtin(x) __has_builtin(x) +#else +#define pg_has_builtin(x) 0 +#endif + /* * Attribute macros * -- 2.53.0