17 Language support library [language.support]

17.9 Exception handling [support.exception]

17.9.5 uncaught_­exceptions [uncaught.exceptions]

int uncaught_exceptions() noexcept;
Returns: The number of uncaught exceptions.
Remarks: When uncaught_­exceptions() > 0, throwing an exception can result in a call of the function std​::​terminate.