The special operator
__has_builtin (operand) may be used in constant integer contexts and in preprocessor ‘#if’ and ‘#elif’ expressions to test whether the symbol named by its operand is recognized as a built-in function by GCC in the current language and conformance mode. It evaluates to a constant integer with a nonzero value if the argument refers to such a function, and to zero otherwise. The operator may also be used in preprocessor ‘#if’ and ‘#elif’ expressions. The
__has_builtin operator by itself, without any operand or parentheses, acts as a predefined macro so that support for it can be tested in portable code. Thus, the recommended use of the operator is as follows:
#if defined __has_builtin # if __has_builtin (__builtin_object_size) # define builtin_object_size(ptr) __builtin_object_size (ptr, 2) # endif #endif #ifndef builtin_object_size # define builtin_object_size(ptr) ((size_t)-1) #endif
© Free Software Foundation
Licensed under the GNU Free Documentation License, Version 1.3.