Re: Linking automatically with dlopen

[Reuben Thomas]

On Tue, 17 Apr 2007, Ralf Wildenhues wrote:

> If you can find out the set of libraries at 'configure' time, then there
> is no need for dlopen.

There is in my case: I do know the set of libraries at configure time, but I 
can't link against all of them. The particular case I have in mind is 
building a Debian package that can go in main but use libraries that are not 
distributed in main. I can't link normally against such libraries (as that 
would make the package depend on them, and a package in main can't depend on 
a package not in main).

> Doing this fully automatically does not work on any system I know of.
> AIX in some cases allows startup with some symbols not yet defined, but
> that's pretty obscure.  I don't think it works with libs that may or may
> not be present, though.

I don't want symbols to be undefined at startup, I want something (the 
linker? libtool?) to convert symbol references into indirect references via 
pointers initialised at runtime by libdl/libltdl.

> > The use I have in mind is linking CODECs with different licenses into an
> > application without needing to change the code so that the CODECs are
> > dlopened. Then, if certain CODECs are not available, the application can
> > simply give an error message if the user attempts to use them, but the
> > application author doesn't need to write (or in this case, re-write) the
> > code to use dlopen.
>
> This is the typical application for dlopen/lt_dlopen.

Indeed, but I'd rather not have to rewrite modules into this form by hand, 
in particular because for other uses the code can be linked normally, and I 
don't want to depend on libdl/libltdl if I can avoid it.

(The code I have in mind is SoX (sox.sf.net).)

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