__glibc_has_extension   57 lib/cdefs.h    # define __glibc_has_extension(ext) __has_extension (ext)
__glibc_has_extension   59 lib/cdefs.h    # define __glibc_has_extension(ext) 0
__glibc_has_extension  154 lib/libc-config.h # undef __glibc_has_extension