How about this approach?

# include <unistd.h>
# include <signal.h>
# include <string.h>
# include <stdlib.h>

static int fds[2];

static void sgsgvhndlr (int signr)
{
    write (fds[1], &signr, 1);
    _Exit (EXIT_FAILURE);
}

static int err (int exit_code, char *msg)
{
    write (STDERR_FILENO, msg, strlen (msg));
    write (STDERR_FILENO, "\n", 1);
    _Exit (EXIT_FAILURE);
}

int main (void)
{
    int rc;
    pid_t pid;

    rc = pipe (fds);
    if (rc != 0) err (EXIT_FAILURE, "pipe");
    pid = fork ();
    if (pid == -1) err (EXIT_FAILURE, "fork");
    if (pid) {
        rc = read (fds[0], &pid, 1);
        if (rc - 1) err (EXIT_FAILURE, "read");
        write (STDOUT_FILENO, "gdb\n", 4);
        /* execute gdb */
        return EXIT_SUCCESS;
    }
    else {
        struct sigaction sa = {0,};
        sa.sa_handler = sgsgvhndlr;
        rc = sigaction (SIGSEGV, &sa, NULL);
        if (rc) err (EXIT_SUCCESS, "sigaction");
        return *(char*)0;
    }
}