set-unexpected-crt.md

title	description	ms.date	api_name	api_location	api_type	topic_type	f1_keywords	helpviewer_keywords
set_unexpected (CRT)	Learn more about: set_unexpected (CRT)	1/14/2021	set_unexpected	msvcrt.dll msvcr80.dll msvcr90.dll msvcr100.dll msvcr100_clr0400.dll msvcr110.dll msvcr110_clr0400.dll msvcr120.dll msvcr120_clr0400.dll ucrtbase.dll	DLLExport	apiref	set_unexpected	set_unexpected function unexpected function exception handling, termination

set_unexpected (CRT)

Installs your own termination function to be called by unexpected.

Syntax

unexpected_function set_unexpected( unexpected_function unexpFunction );

Parameters

unexpFunction
Pointer to a function that you write to replace the unexpected function.

Return value

Returns a pointer to the previous termination function registered by _set_unexpected so that the previous function can be restored later. If no previous function has been set, the return value may be used to restore the default behavior; this value may be NULL.

Remarks

The set_unexpected function installs unexpFunction as the function called by unexpected. unexpected isn't used in the current C++ exception-handling implementation. The unexpected_function type is defined in EH.H as a pointer to a user-defined unexpected function, unexpFunction that returns void. Your custom unexpFunction function shouldn't return to its caller.

typedef void ( *unexpected_function )( );

By default, unexpected calls terminate. You can change this default behavior by writing your own termination function and calling set_unexpected with the name of your function as its argument. unexpected calls the last function given as an argument to set_unexpected.

Unlike the custom termination function installed by a call to set_terminate, an exception can be thrown from within unexpFunction.

In a multithreaded environment, unexpected functions are maintained separately for each thread. Each new thread needs to install its own unexpected function. Thus, each thread is in charge of its own unexpected handling.

In the current Microsoft implementation of C++ exception handling, unexpected calls terminate by default and is never called by the exception-handling run-time library. There's no particular advantage to calling unexpected rather than terminate.

There's a single set_unexpected handler for all dynamically linked DLLs or EXEs; even if you call set_unexpected your handler may be replaced by another or that you're replacing a handler set by another DLL or EXE.

Requirements

Routine	Required header
set_unexpected	<eh.h>

For more compatibility information, see Compatibility.

See also

Exception handling routines
abort
_get_unexpected
set_terminate
terminate
unexpected