Re: dlopen'ing glibc linked libraries

[John Spencer <maillist-musl@barfooze.de>]

Gabriel Jacobo wrote:
> Hey everyone! First message here...
> 
> I recently found about musl when googling for GLIBC alternatives. I read in
> the FAQ that binary compatibility with GLIBC is not there yet, so my
> question is if this is a priority for the library.

GLIBC compat is already pretty good, given that the glibc stuff was 
compiled in a sane manner (i.e. with the flags that enable 64bit off_t).
for example, it is possible to run Dwarf Fortress:
http://openwall.com/lists/sabotage/2013/11/01/1

it's also possible to run opera with a preloaded .so that provides a few
symbols that musl doesn't provide.

> 
> As a bit of background to my question, let me say that I'm an SDL2
> contributor, and I've tried linking SDL against musl, which seemed to work
> great. I'm linking dynamically BTW (statically linking to musl didn't quite
> work, I didn't research the issue much but it's probably a problem in SDL's
> build system).

statically linked musl does not support dlopen(), so you will have a 
hard time loading plugins (explanation for why it is not supported:
http://www.openwall.com/lists/musl/2012/12/08/4 )

> 
> However, SDL uses dlopen/dlsym heavily to load most of its functionality

i guess this kind of plug-in loading is considered a bad idea by most 
people here...

> (for example, to load the libGL.so.1 binary in order to provide OpenGL
> support), and these binaries depend on GLIBC...so (expectedly?) almost

that's not quite true, sabotage linux builds mesa fine (with 2 minor 
patches).
recipe:
https://github.com/sabotage-linux/sabotage/blob/master/pkg/mesalib#L19
patches:
https://github.com/sabotage-linux/sabotage/blob/master/KEEP/mesalib-fpclassify.patch
https://github.com/sabotage-linux/sabotage/blob/master/KEEP/mesalib-strtod.patch
https://github.com/sabotage-linux/sabotage/blob/master/KEEP/mesalib-strtof.patch

> nothing actually works with the SDL/musl binary.

basically what you should try to do is build all dependencies against musl.

> So, will it ever work?

even if it would work, mixing glibc and musl linked things is far from 
optimal.

> 
> Thanks!

btw, you might be interested in this SDL bug:
https://bugzilla.libsdl.org/show_bug.cgi?id=2019