set-error-mode.md

description	title	ms.date	api_name	api_location	api_type	topic_type	f1_keywords	helpviewer_keywords	ms.assetid
Learn more about: _set_error_mode	_set_error_mode	11/04/2016	_set_error_mode	msvcrt.dll msvcr80.dll msvcr90.dll msvcr100.dll msvcr100_clr0400.dll msvcr110.dll msvcr110_clr0400.dll msvcr120.dll msvcr120_clr0400.dll ucrtbase.dll api-ms-win-crt-runtime-l1-1-0.dll	DLLExport	apiref	set_error_mode _set_error_mode	_set_error_mode function set_error_mode function	f0807be5-73d1-4a32-a701-3c9bdd139c5c

_set_error_mode

Modifies __error_mode to determine a non-default location where the C runtime writes an error message for an error that might end the program.

Important

This API cannot be used in applications that execute in the Windows Runtime. For more information, see CRT functions not supported in Universal Windows Platform apps.

Syntax

int _set_error_mode(
   int mode_val
);

Parameters

mode_val
Destination of error messages.

Return value

Returns the old setting or -1 if an error occurs.

Remarks

Controls the error output sink by setting the value of __error_mode. For example, you can direct output to a standard error or use the MessageBox API.

The mode_val parameter can be set to one of the following values.

Value	Description
_OUT_TO_DEFAULT	Error sink is determined by __app_type.
_OUT_TO_STDERR	Error sink is a standard error.
_OUT_TO_MSGBOX	Error sink is a message box.
_REPORT_ERRMODE	Report the current __error_mode value.

If a value is passed in other than the listed ones, the invalid parameter handler is invoked, as described in Parameter validation. If execution is allowed to continue, _set_error_mode sets errno to EINVAL and returns -1.

When it's used with an assert, _set_error_mode displays the statement that failed in the dialog box, and gives you the option of choosing the Ignore button, so that you can continue to run the program.

Requirements

Routine	Required header
_set_error_mode	<stdlib.h>

Example

// crt_set_error_mode.c
// compile with: /c
#include <stdlib.h>
#include <assert.h>

int main()
{
   _set_error_mode(_OUT_TO_STDERR);
   assert(2+2==5);
}

Assertion failed: 2+2==5, file crt_set_error_mode.c, line 8

This application has requested the Runtime to terminate it in an unusual way.
Please contact the application's support team for more information.

See also

assert Macro, _assert, _wassert