Re: compiling musl on x86_64 linux with pcc

[Rich Felker <dalias@libc.org>]

On Tue, Sep 23, 2014 at 09:05:25PM +0200, u-igbb@aetey.se wrote:
> On Mon, Aug 25, 2014 at 11:46:17AM -0400, Rich Felker wrote:
> > Note that some fixes are needed for
> > pcc-libs:
> > 
> > - You need to remove the broken csu files and replace them with
> >   symlinks to the musl files.
> > 
> > - You need to add __attribute__((__visibility__("hidden"))) to all
> >   external functions in libpcc.
> > 
> > - You need to add -fPIC to the CFLAGS for building libpcc or you get a
> >   broken libpcc (containing textrels) that can't be used for building
> >   libc.so and that's harmful for use with any other shared libs.
> 
> I followed these directions and musl with pcc play along very well for me
> (on i386).
> 
> One strange thing I notice though, which is probably more pcc-related
> than musl (even though this concerns a musl-based toolchain).
> 
> If I build a shared library with pcc without supplying -Wl,-Bsymbolic
> (or -Wl,-Bsymbolic-functions as musl does) then a(ny) binary linked to that
> library segfaults at start even if it does not actually need/use the
> library. I noticed this with libpcap and wonder what is the reason. Adding
> -Wl,-Bsymbolic makes everything work so the code is not exactly broken.
> 
> Wonder if you happen to guess a possible reason for such kind of trouble,
> something that pcc gets wrong? This looks related to runtime linking
> behaviour so possibly not fully offtopic here.

Have you checked that this happens with all libs, or did you only
observe it with libpcap? If you have a minimal example .so file that
causes the crash when loaded, can you post it somewhere I could
download a copy to analyze, and also post the commands you used to
produce it?

Rich