llvm-project/clang/test/Preprocessor/feature_tests.c

// RUN: %clang_cc1 %s -triple=i686-apple-darwin9 -verify -DVERIFY
// RUN: %clang_cc1 %s -E -triple=i686-apple-darwin9
#ifndef __has_feature
#error Should have __has_feature
#endif


#if __has_feature(something_we_dont_have)
#error Bad
#endif

#if  !__has_builtin(__builtin_huge_val) || \
     !__has_builtin(__builtin_shufflevector) || \
     !__has_builtin(__builtin_convertvector) || \
     !__has_builtin(__builtin_trap) || \
     !__has_builtin(__c11_atomic_init) || \
     !__has_feature(attribute_analyzer_noreturn) || \
     !__has_feature(attribute_overloadable)
#error Clang should have these
#endif

#if __has_builtin(__builtin_insanity)
#error Clang should not have this
#endif

#if !__has_feature(__attribute_deprecated_with_message__)
#error Feature name in double underscores does not work
#endif

// Make sure we have x86 builtins only (forced with target triple).

#if !__has_builtin(__builtin_ia32_emms) || \
    __has_builtin(__builtin_altivec_abs_v4sf)
#error Broken handling of target-specific builtins
#endif

// Macro expansion does not occur in the parameter to __has_builtin,
// __has_feature, etc. (as is also expected behaviour for ordinary
// macros), so the following should not expand:

#define MY_ALIAS_BUILTIN __c11_atomic_init
#define MY_ALIAS_FEATURE attribute_overloadable

#if __has_builtin(MY_ALIAS_BUILTIN) || __has_feature(MY_ALIAS_FEATURE)
#error Alias expansion not allowed
#endif

// But deferring should expand:

#define HAS_BUILTIN(X) __has_builtin(X)
#define HAS_FEATURE(X) __has_feature(X)

#if !HAS_BUILTIN(MY_ALIAS_BUILTIN) || !HAS_FEATURE(MY_ALIAS_FEATURE)
#error Expansion should have occurred
#endif

#ifdef VERIFY
// expected-error@+2 {{builtin feature check macro requires a parenthesized identifier}}
// expected-error@+1 {{expected value in expression}}
#if __has_feature('x')
#endif
#endif