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The signal handler may also call a handful of functions, including abort(). (See SIG30-C. Call only asynchronous-safe functions within signal handlers for details of functions that can be safely called from within signal handlers.)

Noncompliant Code Example

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In this noncompliant code example, err_msg is updated to indicate that the SIGINT signal was delivered.

Code Block
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#include <signal.h> #include <stdlib.h> #include <string.h> char *err_msg; void handler(int signum) { strcpy(err_msg, "SIGINT encountered."); } int main(void) { enum { MAX_MSG_SIZE = 24 }; signal(SIGINT, handler); err_msg = (char *)malloc(MAX_MSG_SIZE); if (err_msg == NULL) { /* Handle error condition. */ } strcpy(err_msg, "No errors yet."); /* Main code loop */ return 0; }

Noncompliant Code Example (volatile with the Wrong Type)

This noncompliant code example declares err_msg to be volatile. However, because the type of the err_msg object is not sig_atomic_t, the behavior of the program is still undefined  The err_msg variable is a character pointer and not a variable of type volatile sig_atomic_t.

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

volatile char *err_msg;

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

int main(void) {
  enum { MAX_MSG_SIZE = 24 };
  signal(SIGINT, handler);

  err_msg = (volatile char *)malloc(MAX_MSG_SIZE);
  if (err_msg == NULL) {
    /* Handle error condition. */
  }
  strcpy(err_msg, "No errors yet.");

  /* Main code loop */

  return 0;
}

Compliant Solution (Writing volatile sig_atomic_t)

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