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Different actions must be taken depending on whether or not you desire signal handlers to be persistent.

Persistent handlers

By default, *nix systems leave the handler in place after a signal is generated, whereas Windows system do not.

Non-Compliant Code Example (Windows)

This non-complaint code example fails to persist the signal handler on Windows platforms.

void handler(int signum) {
  /* handling code */
}

Compliant Solution (Windows)

A C99-compliant solution to persist the handler on a Windows system is to rebind the signal to the handler in the first line of the handler itself.

void handler(int signum) {
#ifdef WINDOWS
  signal(signum, handler);
#endif
  /* rest of handling code */
}

Non-persistent handlers

By default, Windows systems reset the signal handler to its default action after a signal is generated, whereas *nix system do not.

Non-Compliant Code Example (*nix)

This non-complaint code example fails to reset the signal handler to its default behavior on *nix systems.

void handler(int signum) {
  /* handling code */
}

Compliant Solution (*nix)

A C99-compliant solution to reset the handler on a *nix system is to rebind the signal to the implementation-defined default handler in the first line of the handler itself.

void handler(int signum) {
#ifdef WINDOWS
  /* windows automatically resets handlers to default */
#else
  signal(signum, SIG_DFL);
#endif
  /* rest of handling code */
}

Risk Analysis

Failure to re-establish a persistent signal handler on Windows platforms understand implementation-specific details regarding signal handler persistence can lead to unexpected behavior.

References

\[[ISO/IEC 9899-1999TR2|AA. C References#ISO/IEC 9899-1999]\] "The {{signal}} function"