Page History

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#include <signal.h>

sig_atomic_t interrupted;   /* Bug: not declared volatile */

void sigint_handler(int signum) {
  interrupted = 1;   /* Assignment may not be visible in main() */
}

int main(void) {
  signal(SIGINT, sigint_handler);
  while (!interrupted) {   /* Loop may never terminate */
   /* Do something... */
  }
  return 0;
}

Compliant Solution

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#include <signal.h>

volatile sig_atomic_t interrupted;

void sigint_handler(int signum) {
  interrupted = 1;
}

int main(void) {
  signal(SIGINT, sigint_handler);
  while (!interrupted) {
   /* Do something... */
  }
  return 0;
}

The sig_atomic_t type is the integer type of an object that can be accessed as an atomic entity even in the presence of asynchronous interrupts. The type of sig_atomic_t is implementation-defined, though it provides some guarantees. Integer values ranging from SIG_ATOMIC_MIN through SIG_ATOMIC_MAX may be safely stored to a variable of the type. In addition, when sig_atomic_t is a signed integer type, SIG_ATOMIC_MIN must be no greater than -127 and SIG_ATOMIC_MAX no less than 127. Otherwise, SIG_ATOMIC_MIN must be 0 and SIG_ATOMIC_MAX must be no less than 255. The macros SIG_ATOMIC_MIN and SIG_ATOMIC_MAX are defined in the header <stdint.h>.

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