Build and override a simple winelib DLL

[Maxime Sednaoui]

Hi,

It works, thank you ! Sorry, it was a silly mistake... I added
"__declspec(dllexport)" in mylib_main.c and it was done !
I really appreciate your help, I spent an awful amount of time on it.

Best,


On Sat, Apr 6, 2013 at 5:42 AM, Charles Davis <cdavis5x at gmail.com> wrote:

>
> On Apr 5, 2013, at 10:34 AM, Maxime Sednaoui wrote:
> > Hi,
> >
> > First, I already asked for the same thing at the forum where  I've been
> told to post here for my question
> > Link here : http://forum.winehq.org/viewtopic.php?f=8&t=18675
> >
> > I have a Windows executable that load a really simple DLL (it is a test)
> and I want to create a Winelib DLL that will override the Windows DLL.
> Basically, I created mylib_main.c and mylib.spec to build the Winelib DLL
> with the command:
> > winegcc -mwindows -o mylib.dll.so mylib_main.c -I${WINE_ROOT}/include
> -shared mylib.spec
> > winebuild -w --def -o libmylib.def --export mylib.spec
> >
> > Now I have mylib.dll.so and I want to override mylib.dll
> > What should I do ? I removed the Windows library but then I got a Page
> Fault when the function is called. I also tried to configure the override
> with winecfg or set environment variables like WINEDLLPATH or add a DllMain
> in my library. I don't understand how to proceed.
> >
> > Is this because of the way I build my library ? Or maybe I forget a step
> to link it properly ?
> Actually, it's much simpler than that.
>
> Your Winelib DLL doesn't export a function called myfunc(), but the native
> DLL does. (Try running:
>
>  $ winedump -jexport mylib.dll
>
> to see what I mean.)
>
> Your test app LoadLibrary()'s mylib.dll, then GetProcAddress()'s myfunc()
> from it. (I know this because it doesn't directly call myfunc(). Run:
>
>  $ winedump -jimport myapp.exe
>
> to verify this.) When it does this with your Winelib DLL, GetProcAddress()
> returns NULL and your program crashes--probably because it doesn't check
> for NULL before calling the function. (Of course, the whole point of
> GetProcAddress() is to be able to check if a function exists in a DLL
> before calling it. If you don't check for NULL, then why bother with it in
> the first place? But I digress.)
>
> Chip
>
>
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