Question

The following code triggers a segmentation fault at exit.
It seems to happen only if data is allocated on the stack between the ‘sigaction’ call and the loop :

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

bool end = false;
void handler(int)  {
 end = true; 
}

int main()  {
 struct sigaction sigs;
 sigs.sa_handler = handler;
 sigaction(SIGINT, &sigs, NULL);

 int i;

 while (!end)
  sleep(1);
 return 0;
}

Run and stop with ctrl-C

-> with line ‘int i’ on : segmentation fault

-> without line ‘int i’ : exit ok

(compiled with g++ v4.1.1, OS linux kernel 2.6.19)

sounds like a stack release problem … anyone has an explanation ?

Thanks,

Answer 1

You should initialize all members of your struct sigaction ,as to not risk having it contain garbage, there’s flags/etc. in there that alter the behavior of sigaction()
Do

struct sigaction args = {}; 

or

memset(&args,0,sizeof args);