le billet originel sur le problème :
http://benjamin.smedbergs.us/blog/2008-01-10/patching-the-windows-crt/

On ne peut pas prendre simplement le CRT de mingw car il appelle à son tour msvcrt.dll :
http://groups.google.fr/group/mozilla.dev.platform/msg/eed5febe9ef5ad84

> Well… MinGW calls into msvcrt.dll (the VC6 runtime, shipped with
> Windows; there’s a 64 bit version on 64 bit Windows, too) to do the
> actual malloc() call. That’s not going to help, at all.

Sinon, quelques CRT alternatives mais pas très utilisables, stables, maintenues :
http://mingwacr.sourceforge.net/
http://synesis.com.au/software/cruntiny/
http://wcrt.sourceforge.net/

Le bug sur l’intégration de l’allocator:
https://bugzilla.mozilla.org/show_bug.cgi?id=407459

La meilleurs solution serait probablement d’utiliser Wine :
http://source.winehq.org/source/dlls/msvcrt
http://source.winehq.org/source/dlls/msvcr71

Mais ce source est officiellement incomplet, ne gère pas la partie C++ :
http://www.winehq.org/pipermail/wine-devel/2008-May/065504.html

Wine has its own increasingly useful implementation of msvcrt,
at least the part that uses the C api. (The C++ api is difficult for us
because it has to be written in C; g++ uses a different ABI than Microsoft C++.)

Reste à suivre les évolutions de dév:
http://source.winehq.org/git/wine.git/?a=history;f=dlls/msvcrt;hb=HEAD
http://source.winehq.org/git/wine.git/?a=history;f=dlls/msvcr71;hb=HEAD