Question

I have this code

static void sigXCPU(int pTmp){
  cout<<" .... ";
}

.....
pid_t vPid=fork(); 
  int vStat;   

  switch(vPid){
  case -1: perror("fork");
    exit(1);
  case 0:
    //limit on data
    struct rlimit vLimD;
    vLimD.rlim_cur = 100000; 
    vLimD.rlim_max =  1000000; 
    setrlimit(RLIMIT_DATA, &vLimD);
    //limit on cpu time
    struct rlimit vLimCPU;
    vLimCPU.rlim_cur = 1;
    vLimCPU.rlim_max = 1;

    execl("./p1","",NULL);    
    if(signal(SIGXCPU,sigXCPU)==SIG_ERR);
    break;
  default: 
    while(wait(&vStat)!=vPid);
    break;}

and the code for p1 is

int main(){
  sleep(10);
return 0;}

Why does the child ignore SIGXCPU?The code are compiled with gcc under FreeBsd 8.0 amd64.

Answer 1

The code in the child after execl is never executed, because the current process image is replaced with the application in p1.

Even if you were to put the signal handler before the execl, it would be overriden, because signal dispositions are reset to their defaults after an exec. After all, your handler function would no longer exist in the new process image.

Finally, to set up a signal handler, avoid using signal and use sigaction, instead.