Defined in header <csignal>
typedef /* unspecified */ sig_atomic_t;

An integer type which can be accessed as an atomic entity even in the presence of asynchronous interrupts made by signals.

Notes

Until C++11, which introduced std::atomic and std::atomic_signal_fence, about the only thing a strictly conforming program could do in a signal handler was to assign a value to a volatile static std::sig_atomic_t variable and promptly return.

See also

signal	sets a signal handler for particular signal (function) [edit]
atomic_signal_fence (C++11)	fence between a thread and a signal handler executed in the same thread (function) [edit]
C documentation for sig_atomic_t