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Date: Tue, 23 Sep 2014 15:31:34 -0400
From: Rich Felker <dalias@...c.org>
To: u-igbb@...ey.se
Cc: musl@...ts.openwall.com
Subject: Re: compiling musl on x86_64 linux with pcc
On Tue, Sep 23, 2014 at 09:05:25PM +0200, u-igbb@...ey.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
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