`_set_error_mode`

Artikel
10/26/2022

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.

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