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

From: David Henningsson
Subject: Re: [fluid-dev] Jack Driver for Fluidsynth Windows Build
Date: Mon, 18 Apr 2011 11:38:42 +0200
User-agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv: Gecko/20110411 Thunderbird/3.1.9

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:


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
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 

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

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