Error message "segmentation fault (core dumped)"-CodePudding

I'm trying to run the following C program:

/*
 * Illustrates system call fork
 */

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>

int
main (
  int argc,
  char *argv[]
  )
{
  int tC, tF;
  pid_t pid;

  tC = atoi (argv[1]);
  tF = atoi (argv[2]);

  fprintf (stdout, "Main  :                  ");
  fprintf (stdout, "PID=%d; My parent PID=%d\n",
    getpid(), getppid());

  pid = fork();
  if (pid == 0){
    // Child
    sleep (tC);

    fprintf(stdout, "Child : PIDreturned=%d    ", pid);
    fprintf (stdout, "PID=%d; My parent PID=%d\n",
      getpid(), getppid());
  } else {
    // Father
    sleep (tF);

    fprintf(stdout, "Father: PIDreturned=%d ", pid);
    fprintf (stdout, "PID=%d; My parent PID=%d\n",
      getpid(), getppid());
  }

  return 0;
}

I'm able to compile the code, but when I try to run the executable file I get a "segmentation fault (core dump)" error message.

Can anyone tell me what is causing such issue and how to fix it?

CodePudding user response：

You are not checking if the user supplied any arguments. If fewer than 2 arguments are supplied to the program, it'll do atoi on argv out of bounds (which has undefined behavior and the program may crash as a result).

I suggest that you check it directly at start of main. Example:

int main(int argc, char* argv[]) {
    if(argc != 3) {
        fprintf(stderr, "USAGE: %s child-sleeptime parent-sleeptime\n", argv[0]);
        return 1;
    }

    // ... the rest of `main`