18 Exception handling [except]

18.5 Special functions [except.special]

The function std​::​terminate() is used by the exception handling mechanism for coping with errors related to the exception handling mechanism itself.
The function std​::​current_­exception() and the class std​::​nested_­exception can be used by a program to capture the currently handled exception.

18.5.1 The std​::​terminate() function [except.terminate]

In some situations exception handling must be abandoned for less subtle error handling techniques.
[Note
:
These situations are:
end note
]
In the situation where no matching handler is found, it is implementation-defined whether or not the stack is unwound before std​::​terminate() is called.
In the situation where the search for a handler encounters the outermost block of a function with a non-throwing exception specification, it is implementation-defined whether the stack is unwound, unwound partially, or not unwound at all before std​::​terminate() is called.
In all other situations, the stack shall not be unwound before std​::​terminate() is called.
An implementation is not permitted to finish stack unwinding prematurely based on a determination that the unwind process will eventually cause a call to std​::​terminate().

18.5.2 The std​::​uncaught_­exceptions() function [except.uncaught]

An exception is considered uncaught after completing the initialization of the exception object until completing the activation of a handler for the exception ([except.handle]).
This includes stack unwinding.
If an exception is rethrown ([expr.throw], [propagation]), it is considered uncaught from the point of rethrow until the rethrown exception is caught.
The function std​::​uncaught_­exceptions() returns the number of uncaught exceptions in the current thread.