Synopsis

Shared objects in a signal handler are accessed or modified.

Enabled by default

Yes

Severity/Certainty

High/Low

Full description

Accessing or modifying shared objects (not of the type volatile sig_atomic_t) in a signal handler might result in race conditions that can leave data in an inconsistent state.

Coding standards

Code examples

The following code example fails the check and will give a warning:

#include <signal.h>
#include <stdlib.h>
#include <string.h>

enum { MAX_MSG_SIZE = 24 };
char *err_msg;

void handler(int signum) {
  strcpy(err_msg, "SIGINT encountered.");
}

int main(void) {
  signal(SIGINT, handler);

  err_msg = (char *)malloc(MAX_MSG_SIZE);
  if (err_msg == NULL) {
    /* Handle error */
  }
  strcpy(err_msg, "No errors yet.");
  /* Main code loop */
  return 0;
}

The following code example passes the check and will not give a warning about this issue:

#include <signal.h>
#include <stdlib.h>
#include <string.h>

enum { MAX_MSG_SIZE = 24 };
volatile sig_atomic_t e_flag = 0;

void handler(int signum) {
  e_flag = 1;
}

int main(void) {
  char *err_msg = (char *)malloc(MAX_MSG_SIZE);
  if (err_msg == NULL) {
    /* Handle error */
  }

  signal(SIGINT, handler);
  strcpy(err_msg, "No errors yet.");
  /* Main code loop */
  if (e_flag) {
    strcpy(err_msg, "SIGINT received.");
  }
  return 0;
}