SIGINT default behaviour not restored when using SING_DFL

Question

I'm trying to implement my own shell that exits on ctrl+d (and not ctrl+C) To do that, I want my program to ignore SIGINT so I used

signal(SIGINT, SIG_IGN);

but I do want the programs I'm running in the shell to exit on ctrl+c, so after each fork(), in the child process, I'm trying to restore the default behavior using

signal(SIGINT, SIG_DFL);

but unfortunately SIGING is still ignored. What am I missing? thank you!

EDIT: As mentioned in the comments problem was that SIGINT did not reach the child process. If I understand correctly this is because exec will reset only the handlers for caught signals, and in my case I ignored sigint. to fix this I replaced signal(SIGINT, SIG_IGN) with my own handler that does nothing:

void sigint_signal_handler(int signum) {
    printf("testttttt");
}

int register_signal_handling() {
    struct sigaction sigint_action;
    memset(&sigint_action, 0, sizeof(sigint_action));
    sigint_action.sa_handler = sigint_signal_handler;
    return sigaction(SIGINT, &sigint_action, NULL);
}

int main(void) {
     if (register_signal_handling() == -1) {
         perror("signal handler registration error");
      exit(1);
     }
     return 0;
}

What happens now is weird - when I do ctrl+c I see "testttttt" printed, but it still exits the program. how is this possible if the handler is replaced? Thank you

Exec will reset all handlers of the child to default anyway [see also](https://stackoverflow.com/questions/2333637/is-it-possible-to-signal-handler-to-survive-after-exec). It's more likely that SIGINT is not being delivered to the child in the first place. Try adding a handler to the shell and the executed program that prints which PID got the signal and see for yourself. — , Nov 11 '21 at 09:51

SIGINT default behaviour not restored when using SING_DFL

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