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Q124520: FILE: Increased File Libraries for Visual C++ 2.0-2.2 Available

Article: Q124520
Product(s): Microsoft C Compiler
Version(s): 2.0,2.1,2.2
Operating System(s): 
Keyword(s): kbfile kbProgramming kbCRT kbVC
Last Modified: 06-FEB-2002

-------------------------------------------------------------------------------
The information in this article applies to:

- The C Run-Time (CRT), used with:
   - Microsoft Visual C++, 32-bit Editions, versions 2.0, 2.1, 2.2 
-------------------------------------------------------------------------------

SUMMARY
=======

The run-time libraries have a preset limit on the number of files you can have
open at one time as described in the More Information section of this article.

You can, however, increase these limits by downloading the Increased File Handle
Libraries for Microsoft Visual C++, 32-bit Edition, versions 2.0, 2.1 and 2.2.
Download Vc20xf.exe for Visual C++ 2.0, or Vc22xf.exe for Visual C++ 2.1 and
2.2.

The following files are available for download from the Microsoft Download
Center:

Vc20xf.exe

Vc22xf.exe

For additional information about how to download Microsoft Support files, click
the article number below to view the article in the Microsoft Knowledge Base:

  Q119591 How to Obtain Microsoft Support Files from Online Services

Microsoft used the most current virus detection software available on the date of
posting to scan this file for viruses. Once posted, the file is housed on secure
servers that prevent any unauthorized changes to the file.

For more information about downloading files from the Microsoft Software Library,
please see the following article in the Microsoft Knowledge Base:

  Q119591 How to Obtain Microsoft Support Files from Online Services


MORE INFORMATION
================

Preset Limits
-------------

Attempting to open more than 64 file handles (or 20 file streams) concurrently in
a process will fail if you are creating a single- threaded application that uses
the static run-time library (LIBC.LIB) by using the /ML compiler option (the
default).

Attempting to open more than 256 files handles (or 40 file streams) concurrently
in a process will fail if you are using the static multi-threaded run-time
library by using the /MT compiler option and LIBCMT.LIB. The same limit applies
if you use the DLL version of the run-time library by using the /MD compiler
option and MSVCRT.LIB or MSVCRT20.DLL.

Increased Limits Using the Files in VC20XF.EXE & VC22XF.EXE
-----------------------------------------------------------

VC20XF.EXE ans VC22XF.EXE include the following five files:

+-------------------------------------------------------------------+
| README.TXT   | File containing instructions on use of these .LIBs | 
+-------------------------------------------------------------------+
| LIBC.LIB     | Single threaded run-time library                   | 
+-------------------------------------------------------------------+
| LIBCMT.LIB   | Multi-threaded run-time library                    | 
+-------------------------------------------------------------------+
| MSVCRT2X.LIB | Import library for MSVCRT2X.DLL                    | 
+-------------------------------------------------------------------+
| MSVCRT2X.DLL | Multi-threaded run-time library in a DLL.          | 
+-------------------------------------------------------------------+

These run-time libraries have been rebuilt to allow the use of up to 509 file
handles and up to 125 file streams in an application. The total is actually 512
handles and 128 streams, but three handles and streams are used by the run-time
library for the standard C input/output/error files, stdin, stdout, and stderr.
Note that each stream (FILE*) uses a handle, so the two limits are not
independent of each other.

When building your application, the libraries must be in your current directory,
or in a directory specified by the LIB environment variable. If you place them
in the \MSVC20\LIB directory, make a backup copy of the existing libraries of
the same name.

For MSVCRT2X.LIB to be used as a default library, you must rename it to
MSVCRT.LIB. If you use this library, MSVCRT2X.DLL must be in the path or in the
Windows system directory. You may distribute MSVCRT2X.DLL with applications
built with MSVCRT2X.LIB.

These files are provided for the convenience of Visual C++ users; they are
provided as is without any support.

File handles are obtained when you use the low-level I/O functions (_open and
_sopen, and _creat) to open a file. When one of these functions fails because
the application has reached the file limit, they will return -1, and set the
global variable errno to the constant EMFILE. EMFILE is defined in ERRNO.H as
24.

File handles are also associated with the iostream classes. When a member
function or constructor of an iostream class fails because the application has
reached the file limit, the bad member function will return a nonzero value.
Note that many other types of errors can also cause the bad member function to
return a nonzero value.

File streams are associated with the stream I/O functions (fopen, _fdopen, and
_fsopen). When one of these functions fails because the application has reached
the file limit, they will return NULL. Note that many other types of file stream
errors can also cause the functions to return NULL.

NOTE: You must call SetHandleCount() to increase the number of file handles
available on WIN32s. This function changes the number of file handles available
to a process. Under Win32s, this default is 20. It has no effect when called
under Windows NT.

Additional query words: runtime vc++

======================================================================
Keywords          : kbfile kbProgramming kbCRT kbVC 
Technology        : kbVCsearch kbAudDeveloper kbCRT
Version           : :2.0,2.1,2.2

=============================================================================

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