Re: [Mingw-users] Linking against the Dirac LE msvc lib

[Olivier G. <li...@sa...>]

Marc Vaillant wrote:
> On Mon, May 18, 2009 at 11:53:16PM +0200, Olivier Guilyardi wrote:
>> Jim Marshall wrote:
>>> Olivier Guilyardi wrote:

[...]

>>>> LIBRARY "DiracLE.dll"
>>>> EXPORTS
>>>> ?DiracCreate@@YAPAXJJJMP6AJPAMJPAX@Z@Z
>>>> ?DiracCreate@@YAPAXJJJMP6AJPAPAMJPAX@Z@Z
>>>> ?DiracDestroy@@YAXPAX@Z
>>>> ?DiracGetInputBufferSizeInFrames@@YAJPAX@Z
>>>> ?DiracGetProperty@@YAOJPAX@Z
>>>> ?DiracProcess@@YAJPAMJPAX1@Z
>>>> ?DiracProcess@@YAJPAPAMJPAX1@Z
>>>> ?DiracReset@@YAX_NPAX@Z
>>>> ?DiracSetProperty@@YAJJOPAX@Z
>>>> ?DiracVersion@@YAPBDXZ
>>>>
>>>>
>>> Looks like those are C++ functions, presumably the DLL was compiled with 
>>> the Microsoft C++ compiler. Unfortunately you can not mix C++ code from 
>>> different vendors since each vendor has there own 'name mangling' scheme.
> 
> This is not exactly correct.  Yes, C++ name mangling is different across
> vendors, however Any vendor that supports COM is  vtable ABI compatible.
> Please consult http://aegisknight.org/cppinterface.html which outlines
> how to create binary compatible C++ interfaces.  The basic idea is for
> your classes to have only virtual functions, and to have C factory
> methods for creating instances of them.   
> 
>> Thanks for your answer.
>>
>> Do you think I could write a small C'ish wrapping library around DiracLE,
>> compile it with msvc and then link this in mingw? Could I export (reimp
>> friendly) C symbols from my wrapper, knowing that it will itself be linked with
>> the DiracLE C++ library?
> 
> Yes, you can do this.  If you want your wrapper to be C++ then you can
> also do that by following the article I reference above.

Thanks for this pointer. However, in the meantime I managed to dynamically load
the DLL and map the (three) functions that I need using win32's LoadLibrary()
and GetProcAddress() (all of this from my mingw compiled app).

For instance (shortened):

#include <windows.h>

typedef long (__cdecl *ProcessFunction)(float **audioOut, long numFrames,
                                        void *userData, void *dirac);

HINSTANCE dll = LoadLibrary(TEXT("DiracLE.dll"));
ProcessFunction diracProcess =
    (ProcessFunction) GetProcAddress(dll, "?DiracProcess@@YAJPAPAMJPAX1@Z");

I have some stability problems (but chances are high that this comes from my
alpha-state code), and it looks like gdb's getting confused (but this could be
caused by multi-threading). Note: I'm actually using QtCreator, which manages
all mingw compilation by itself.

But all in all, this dynamic "linking" works :)

Is there any reason why I shouldn't do that?

--
  Olivier