Is there a way to redefine malloc at link time on Windows?

Question

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         


        

Answer 1

What about defining malloc=_custom_malloc in the project makefile. Than adding a file such as:

my_memory.c
#undef malloc
#undef calloc
...
void *_custom_malloc(int size) { return jmalloc(size); }
void *_custom_calloc(int size) { return jcalloc(size); }
...

Answer 2

I think it depends in which order you link the files. I think you need to link your custom function first, then the import library.

Answer 3

From version 3.0 Firefox uses a custom allocator (AFAIR jmalloc) -- you could check how they did it. I read that they had some problems with it. You may check this blog post.

Answer 4

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."