MSVC and MinGW DLLs | MinGW

MSVC and MinGW DLLs | MinGW
Assume we have a testdll.h, testdll.c, and testmain.c. In the first case, we will compile testdll.c with MinGW, and let the MSVC-compiled testmain call it. You should use

gcc -shared -o testdll.dll testdll.c -Wl,--output-def,testdll.def,--out-implib,libtestdll.a

to produce the DLL and DEF files. MSVC cannot use the MinGW library, but since you have already the DEF file you may easily produce one by the Microsoft LIB tool:

lib /machine:i386 /def:testdll.def

Once you have testdll.lib, it is trivial to produce the executable with MSVC:

cl testmain.c testdll.lib

Now for MinGW programs calling an MSVC DLL. We have two methods. One way is to specify the LIB files directly on the command line after the main program. For example, after

cl /LD testdll.c

use

gcc -o testmain testmain.c testdll.lib

The other way is to produce the .a files for GCC. For __cdecl functions (in most cases), it is simple: you only need to apply the reimp tool from Anders Norlander (since his web site is no longer available, you may choose to download [this version|http://jrfonseca.dyndns.org/projects/gnu-win32/software/reimp/index.html] enhanced by Jose Fonseca):

reimp testdll.lib
gcc -o testmain testmain.c -L. -ltestdll

However, for __stdcall functions, the above method does not work. For MSVC will prefix an underscore to __stdcall functions while MinGW will not. The right way is to produce the DEF file using the pexports tool included in the mingw-utils package and filter off the first underscore by sed:

pexports testdll.dll | sed "s/^_//" > testdll.def

Then, when using dlltool to produce the import library, add `-U' to the command line:

dlltool -U -d testdll.def -l libtestdll.a

And now, you can proceed in the usual way:

gcc -o testmain testmain.c -L. -ltestdll

Hooray, we got it.