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Q143072: HOWTO: Determine Default Libraries for an .OBJ Object File

Article: Q143072
Product(s): Microsoft C Compiler
Version(s): 2.0,2.1,2.2,4.0,5.0,6.0
Operating System(s): 
Keyword(s): kbVC200 kbVC210 kbVC400 kbVC500 kbVC600
Last Modified: 26-MAR-2002

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The information in this article applies to:

- Microsoft Visual C++, versions 2.0, 2.1, 2.2, 4.0 
- Microsoft Visual C++, 32-bit Enterprise Edition, versions 5.0, 6.0 
- Microsoft Visual C++, 32-bit Professional Edition, versions 5.0, 6.0 
- Microsoft Visual C++, 32-bit Learning Edition, version 6.0 
- Microsoft Visual C++.NET (2002) 
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SUMMARY
=======

In Visual C++, default libraries can be linked to automatically. This is done
for the C run-time libraries. The compiler writes a default C run-time library
name in the object (.obj) files it creates. The library name depends on the
compiler options you use. For additional information, please see the following
article in the Microsoft Knowledge Base:

  Q128641 The /Mx Compiler Options and the LIBC, LIBCMT, MSVCRT Libs

You can also specify default libraries by the using the #pragma comment()
compiler directive. The Microsoft Foundation Class (MFC) header files do this.

Writing a default library name in an object file in this manner saves you from
having to specify the library on the linker command line. However, sometimes it
is necessary to determine which libraries an object file links to by default.

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

To see which libraries an object file will use by default, you can use the
Dumpbin.exe utility in a console session. For example, to find out which
libraries Mfcapp.obj will cause the linker to search automatically, you would
use the following code (this example pipes the output to a file):

     DUMPBIN /RAWDATA /SECTION:.drectve MFCAPP.OBJ > OUTPUT.TXT

In the column to the right side of the output, you'll see the list of default
libraries; the following is an excerpt from that column:

-default|lib:mfc4
0.lib -d|efaultli
b:mfcs40|.lib -de
faultlib|:msvcrt.
lib -def|aultlib:
kernel32|.lib -de
faultlib|:user32.
lib

From this excerpt, you can determine this object file will cause the linker to
automatically search Mfc40.lib, Msvcrt.lib, Kernel32.lib, and User32.lib when
building an executable file. As you can see, each library name is preceded with
"-defaultlib:". You can use this procedure for multiple object files, and
compare the output of each file.

One reason you may need to determine which default library names are in an object
file is to troubleshoot the LNK2005 error, "symbol multiply defined."

Additional query words:

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Keywords          : kbVC200 kbVC210 kbVC400 kbVC500 kbVC600 
Technology        : kbVCsearch kbVC400 kbAudDeveloper kbVC220 kbVC500 kbVC600 kbVC200 kbVC210 kbVC32bitSearch kbVCNET kbVC500Search
Version           : :2.0,2.1,2.2,4.0,5.0,6.0
Issue type        : kbhowto

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