std::sig_atomic_t
Min standard notice:
Header: <csignal>
An integer type which can be accessed as an atomic entity even in the presence of asynchronous interrupts made by signals.
# Declarations
typedef /* unspecified */ sig_atomic_t;
# 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.