A signal handler should not reassert its desire to handle its own signal. This is often done on non-persistent platforms, that is, platforms that, upon receiving a signal, unbind the signal to default behavior before calling the bound signal handler. See SIG01-A. Understand implementation-specific details regarding signal handler persistence.
A signal handler may only call signal() if it does not need to be asynchronous-safe (in other words, all relevant signals are masked, and consequently it may not be interrupted.)
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| Code Block | ||
|---|---|---|
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void handler(int signum) {
#ifndef WINDOWS
signal(signum, SIG_DFL);
#endif
/* handle signal */
}
/* ... */
signal(SIGUSR1, handler);
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Risk Assessment
Two signals in quick succession can trigger the race condition on non-persistent platforms, causing the signal's default behavior despite a handler's attempt to override it.
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