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# Compiler features
check_c_source_compiles(
"unsigned int x = 11; int main() { return __builtin_clz(x); }"
HAVE__BUILTIN_CLZ)
check_c_source_compiles(
"unsigned int x = 11; int main() { return __builtin_popcount(x); }"
HAVE__BUILTIN_POPCOUNT)
check_c_source_compiles(
"int i=0; int main() { return __builtin_expect(i, 0) ? 0 : 1; }"
HAVE___BUILTIN_EXPECT)
check_c_source_compiles(
"__thread int i=0; int main() { return 0; }"
HAVE___THREAD)
check_c_source_compiles(
"volatile int i=0; int main() { return 0; }"
HAVE_VOLATILE)
check_c_source_compiles(
"static inline int foo() { return 0; } int main() { return foo(); }"
HAVE_INLINE)
check_c_source_compiles(
"int main() { void *p = &&lbl; goto *p; lbl: return 0; }"
O_LABEL_ADDRESSES)
check_c_source_runs(
"extern int __attribute__((weak)) foo(); int main() { return &foo == 0 ? 0 : 1; }"
HAVE_WEAK_ATTRIBUTE)
function(check_visibility)
set(CMAKE_REQUIRED_FLAGS ${CMAKE_REQUIRED_FLAGS} -Werror)
check_c_source_compiles(
"int foo __attribute__((visibility (\"hidden\"))) = 1; int main() { return 0; }"
HAVE_VISIBILITY_ATTRIBUTE)
if(HAVE_VISIBILITY_ATTRIBUTE)
set(HAVE_VISIBILITY_ATTRIBUTE 1 PARENT_SCOPE)
endif()
endfunction()
check_visibility()
# Builtin functions that lead to conflicts
check_c_source_compiles(
"#include <alloca.h>\nint main() { char *s = alloca(10); return s!=0; }"
HAVE_ALLOCA)
check_c_source_compiles(
"#include <math.h>\nint main() { double x = 0.0; return signbit(x); }"
HAVE_SIGNBIT)
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