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Asked: 2026-05-10T16:34:57+00:00

I would like to replace the default malloc at link time to use a

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I would like to replace the default malloc at link time to use a custom malloc. But when I try to redefine malloc in my program, I get this error:

MSVCRT.lib(MSVCR80.dll) : error LNK2005: _malloc already defined in test.lib(test.obj)

This works perfectly on any Unix, and it works on Windows with most functions, but not with malloc. How can I do this? And what is different with malloc that disallow overriding it?

I know I could replace every call to malloc with my custom malloc, or use a macro to do this, but I would rather not modify every third party library.

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  1. There is really good discussion of how hard this is here:

    http://benjamin.smedbergs.us/blog/2008-01-10/patching-the-windows-crt/

    Apparently, you need to patch the CRT

    Edit: actually, a MS employee gave the technique in the discussion. You need to move your malloc to a lib, and then link it before the CRT

    ‘he also mentions that if you link your malloc as a lib before the CRT (i.e. make sure to turn on ‘ignore default libs’ and explictly include the CRT), you’ll get what you want, and can redistribute this lib without problems.’

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