18 Language support library [language.support]

18.8 Exception handling [support.exception]

18.8.4 uncaught_exception [uncaught]

bool uncaught_exception() noexcept;

Returns: true after the current thread has initialized an exception object ([except.throw]) until a handler for the exception (including std::unexpected() or std::terminate()) is activated ([except.handle]). [ Note: This includes stack unwinding ([except.ctor]).  — end note ]

Remarks: When uncaught_exception() returns true, throwing an exception can result in a call of std::terminate() ([except.terminate]).