13 Exception handling [except]

13.5 Special functions [except.special]

13.5.1 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 such cases, the function std​::​terminate is called.
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 the function std::terminate is called.
In all other situations, the stack shall not be unwound before the function 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 the function std::terminate.