test.c

#include <errno.h>
#include <stdio.h>
#include <stdlib.h>
#include <signal.h>
#include <sys/prctl.h>

pid_t pid1;

void mhandler(int signum) {
        fprintf(stderr, "parent got signal %d\n", signum);
        if (pid1 > 0) {
                kill(pid1, signum);
        }
}

int main(int argc, char *argv[]) {
        pid1 = fork();
        if (pid1 == 0) {
                prctl(PR_SET_PDEATHSIG, SIGKILL, 0, 0, 0);
                execv("something", argv);
        } else {
                signal(SIGINT, mhandler);
                signal(SIGHUP, mhandler);
                signal(SIGTERM, mhandler);
                int status = 0;
                if (waitpid(pid1, &status, NULL) == -1) {
                        exit(1);
                }
        }

        return 0;
}