trap.c

// valid values for each: 0-2, where 0 is "do nothing"
#define SIGNAL_MODE 1
#define RAISE_MODE 2

#include <signal.h>
#include <stdio.h>

void handler(int _)
{
    // In general it is not safe to call stdio functions from a signal
    // handler, but in this case it only called from a particular place
    // in main so happens to be safe.
    puts("signal");
}

int main()
{
#if SIGNAL_MODE == 1
    signal(SIGTRAP, SIG_IGN);
#endif
#if SIGNAL_MODE == 2
    signal(SIGTRAP, handler);
#endif
#if RAISE_MODE == 1
    raise(SIGTRAP);
#endif
#if RAISE_MODE == 2
    asm("int3");
#endif
    puts("Hello, World!");
}