A C test script to print out what macros the compiler adds to the compilation environment.

macro_test.c

#include <stdio.h>

/*
 * https://gcc.gnu.org/onlinedocs/cpp/Stringizing.html
 * https://hmijailblog.blogspot.com/2016/03/an-isdefined-c-macro-to-check-whether.html
 */
#define str(s) #s
#define xstr(s) str(s)
#define quote(s) str(#s)
#define isdefined(s) (__builtin_strcmp("" #s, str(s)) != 0)
#define print_defined(s)                                 \
	do { if (__builtin_strcmp("" #s, str(s)) != 0) { \
	printf("%-30s: %s\n", #s, quote(s): "");         \
	}} while (0)

int main() {
	print_defined(debug);
	print_defined(DEBUG);
	print_defined(__debug__);
	print_defined(__DEBUG__);

	print_defined(__WIN32__);
	print_defined(__APPLE__);
	print_defined(__LINUX__);
	print_defined(__linux__);

	print_defined(__cplusplus);

	// https://stackoverflow.com/questions/28166565/detect-gcc-as-opposed-to-msvc-clang-with-macro
	print_defined(__GNUG__);
	print_defined(__GNUC__);
	print_defined(__GNUC_MINOR__);
	print_defined(__GNUC_PATCHLEVEL__);
	print_defined(__clang__);
	print_defined(__clang_major__);
	print_defined(__clang_minor__);
	print_defined(__clang_patchlevel__);

	// https://stackoverflow.com/questions/4266354/how-to-tell-if-glibc-is-used
	print_defined(__GNU_LIBRARY__);
	print_defined(__GLIBC__);
	print_defined(__GLIBC_MINOR__);

	/* fcntl.h */
	print_defined(__USE_XOPEN2K);
	print_defined(__USE_FILE_OFFSET64);
	print_defined(__USE_LARGEFILE64);
	print_defined(__REDIRECT_NTH);

	/* man feature_test_macros */
	print_defined(_POSIX_SOURCE);
	print_defined(_POSIX_C_SOURCE);
	print_defined(_GNU_SOURCE);
	print_defined(_XOPEN_SOURCE);
	print_defined(_XOPEN_SOURCE_EXTENDED);
	print_defined(_BSD_SOURCE);
	print_defined(_DEFAULT_SOURCE);
	print_defined(_SVID_SOURCE);
	print_defined(__STRICT_ANSI__);

	print_defined(_ISOC99_SOURCE);
	print_defined(_ISOC11_SOURCE);

	print_defined(_LARGEFILE64_SOURCE);
	print_defined(_LARGEFILE_SOURCE);
	print_defined(_FILE_OFFSET_BITS);
	print_defined(_TIME_BITS);

	print_defined(_REENTRANT);
	print_defined(_FORTIFY_SOURCE);
	return 0;
}