Re: LibJIT / Lightning interoperability issue

[Paul Cercueil]

Hi Daniel,

Le sam. 26 déc. 2020 à 18:54, Daniel Schwen <daniel@schwen.de> a 
écrit :
> Hello list,
>
> I noticed that both the LibJIT as well as Lightning libraries export
> the jit_memcpy, jit_memmove, jit_realloc, and jit_free functions,
> causing crashes when linking to both.
>
> It looks like the functions are only declared in jit_private.h and not
> part of the public API, so I have tried renaming them and this fixes
> the problem:
>
> https://github.com/dschwen/lightning/commit/7bfc7f1e1857790a072ebe441b8fbc506739a873
>
> Another option would be to control symbol export in the build system, 
> which I've done in this commit:
>
> https://github.com/dschwen/lightning/commit/e9ee173fc92b90deb22fa6d5abf5d31505972b0f
>
> I know this is an easy to dismiss issue, but I'm working on a generic
> mathematical expression parsing library with JIT support, and I'd 
> like to
> offer as many options as possible for JIT backends, and am frequently 
> (actually
> always) building and linking against multiple JIT libs. It just seems 
> like good
> software practice not to export unneeded symbols, as they all occupy 
> one single global namespace and the more symbols you export the 
> slower the link times get,

Totally with you on this one.

A third option I suggest, is to compile with -fvisibility=hidden, then 
create a __api macro defined like this:
#define __api __attribute__((visibility ("default")))

Then all the public functions of the library must be prefixed with 
__api.

Cheers,
-Paul