R_API void r_sys_backtrace(void) {
#ifdef HAVE_BACKTRACE
	void *array[10];
	size_t size = backtrace (array, 10);
	eprintf ("Backtrace %zd stack frames.\n", size);
	backtrace_symbols_fd (array, size, 2);
#elif __APPLE__
	void **fp = (void **) __builtin_frame_address (0);
	void *saved_pc = __builtin_return_address (0);
	void *saved_fp = __builtin_frame_address (1);
	int depth = 0;

	printf ("[%d] pc == %p fp == %p\n", depth++, saved_pc, saved_fp);
	fp = saved_fp;
	while (fp) {
		saved_fp = *fp;
		fp = saved_fp;
		if (!*fp) {
			break;
		}
		saved_pc = *(fp + 2);
		printf ("[%d] pc == %p fp == %p\n", depth++, saved_pc, saved_fp);
	}
#else
#ifdef _MSC_VER
#pragma message ("TODO: r_sys_bt : unimplemented")
#else
#warning TODO: r_sys_bt : unimplemented
#endif
#endif
}