FIX: _setmaxstdio Causes Access Violation (145996)

The information in this article applies to:

The C Run-Time (CRT), when used with:
- Microsoft Visual C++, 32-bit Professional Edition 4.0
- Microsoft Visual C++, 32-bit Professional Edition 4.1
- Microsoft Visual C++, 32-bit Professional Edition 4.2
- Microsoft Visual C++, 32-bit Enterprise Edition 4.2
- Microsoft Visual C++, 32-bit Learning Edition 4.0
- Microsoft Visual C++, 32-bit Learning Edition 4.2

This article was previously published under Q145996

SYMPTOMS

The CRT function _setmaxstdio does not work properly. The function sets the maximum number of files an application can open with the stream I/O functions, like fopen. It is documented in the README book in the online documentation, and in the Vcread.wri file.

Using _setmaxstdio results in the following error when you exit the program or call the fopen function:

Unhandled exception in <Project>.exe: 0xC0000005: Access Violation

RESOLUTION

Do not use the _setmaxstdio function. Here are two workarounds:

Keep track of the number of files opened with fopen, and do not open more than 512. -or-
If the application needs to open more than 512 files, use the low-level I/O functions: _open, _read, and _write. These allow up to 2048 files to be opened.

STATUS

Microsoft has confirmed this to be a bug in the Microsoft products listed at the beginning of this article. This bug was corrected in Visual C++ 4.1.

MORE INFORMATION

Sample Code to Reproduce Problem

/* Compile options needed: none
*/ 

#include <stdio.h>

void main()
{
    _setmaxstdio(511);
    FILE *text = fopen("textfile.txt","w");
    fclose(text);
}

Modification Type:	Major	Last Reviewed:	12/9/2003
Keywords:	kbbug kbCRT kbfix kbVC410fix KB145996