> Try -Wsystem-headers.
You're right. That showed a warning. > You need to suppress the macro to get the builtin. That means a macro expansion takes precedence over a builtin function substitution, if I understand correctly. It makes sense, because preprocessing happens before compilation. Maybe we could mention that in the manual, for example in "6.59 Other Built-in Functions Provided by GCC" (https://gcc.gnu.org/onlinedocs/gcc/Other-Builtins.html). Andrea Monaco
