#include <sys/param.h>
#include <sys/types.h>
#include <sys/sysctl.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <err.h>

/*
174 kamil@chieftec /tmp $ gcc isdebugged.c  
175 kamil@chieftec /tmp $ ./a.out           
traced=FALSE
176 kamil@chieftec /tmp $ gdb ./a.out                                                                                                                       
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Reading symbols from ./a.out...(no debugging symbols found)...done.
(gdb) r
Starting program: /tmp/a.out 
[New LWP 1 of process 6373]
traced=TRUE
[Inferior 1 (process 6373) exited normally]
(gdb) q
*/

int
main(int argc, char **argv)
{
	struct kinfo_proc2 p;
	size_t len = sizeof(p);
	
	int name[] = {
		[0] = CTL_KERN,
		[1] = KERN_PROC2,
		[2] = KERN_PROC_PID,
		[3] = getpid(),
		[4] = (int)(sizeof(struct kinfo_proc2)),
		[5] = 1
	};

	const size_t namelen = __arraycount(name);

	if (sysctl(name, namelen, &p, &len, NULL, 0) == -1)
		err(EXIT_FAILURE, "sysctl");

	printf("traced=%s\n", p.p_flag & P_TRACED ? "TRUE" : "FALSE");

	return 0;
}