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A signal is a mechanism for transferring control that is typically used to notify a process that an event has occurred. That process can then respond to that the event accordingly. The C Standard provides functions for sending and handling signals within a C program.

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void (*signal(int sig, void (*func)(int)))(int);

This signal handler is conceptually equivalent to

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Some platforms provide the ability to mask signals while a signal handler is being processed. If a signal is masked while its own handler is processed, the handler is noninterruptible and need not be async-signal-safe. However, even when a signal is masked while its own handler is processed, the handler must still avoid invoking async-signal-safe unsafe functions because their execution may be (or have been) interrupted by another signal.

Vulnerabilities can arise if a signal handler that is not async-signal-safe is interrupted with any unmasked signal, including its own.

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Bibliography

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