Re: [fluid-dev] Jack Driver for Fluidsynth Windows Build

[David Henningsson]

On 2011-04-18 10:35, Stéphane Letz wrote:
> Le 18 avr. 2011 à 08:47, David Henningsson a écrit :
>
> > Hi Graham,
> >
> > I don't want to push the problem back and forward, but in this case I think 
> > it's reasonable to say that:
> >
> > 1) We need to be told by the Jack devs about recommended way to link to the 
> > jack headers.
> > Does that means dynamic linking?
>
> I guess you mean "weak linking" right? (that is the fact that fluidsynth can 
> start even if libjack is not found...)

Dynamic linking is when you look up the function at runtime (using 
LoadLibrary / GetProcAddress in windows), vs static linking where that 
is done by the loader before the program starts. Weak linking is a new 
concept for me and I haven't fully understood it yet.

> > On windows only or on all platforms? Will that still work with e g Jack 1? 
> > Anyway, if we conclude dynamic linking is the way forward, it is reasonable to 
> > think that there should be a version of JackWeakAPI.cpp that is in C and not 
> > C++ (just like the rest of FS).
> > I don't exactly know how difficult it would be to bring C++ code into FS on all 
> > platforms, but it would probably be more difficult than rewriting 
> > JackWeakAPI.cpp in pure C.
>
> Well I think the code in JackWeakAPI.cpp is completely C.... so the file can 
> probably be safely used in C. I'll check again.
>
> Concerning weak linking itself: the thing is that on jack now use (or tries to 
> use...) __attribute__((__weak__)) kind of stuff from GCC, see:
>
> http://trac.jackaudio.org/browser/jack2/trunk/jackmp/common/jack/weakjack.h
>
> but the problem is that  I could not make this work on Windows which uses  
> __declspec(dllexport) stuff to export symbols from the DLL. So on Windows the 
> "compile JackWeakAPI.cpp" is the way to go. On OSX or Linux the more standard 
> way (describe in weakjack.h) can be used.

Ok, I don't mind compiling in JackWeakAPI.c into FluidSynth for the 
Windows build. I'm not sure how this relates to ASIO though, it seems 
like an unrelated problem...?

> > 2) If Jack has an ASIO backend, that's great news! However, looking at
> > http://trac.jackaudio.org/browser/jack2/trunk/jackmp/windows/JackRouter/JackRouter.h
> > it seems to be declared under GPLv2+. I don't see how the end result could be 
> > legally distributed in binary form, when the ASIO headers cannot be freely 
> > distributed.
> OK, but the ASIO headers  are only included to compile JackRouter. What would 
> be the appropriate licence to be able to distribute binaries of JackRouter?

<I'm-not-a-lawyer disclaimer>

As I understand it the library closest to ASIO, i e the library that 
actually needs the ASIO headers to compile, needs to be something very 
permissive, e g BSD.

The rest of the libraries that are linked in, e g FluidSynth, can be 
LGPL. GPL is problematic at all layers.

</I'm-not-a-lawyer disclaimer>

// David