Bug#624354: Processed: Re: Bug#624354: ./xpcshell: error while loading shared libraries: ./libxul.so: R_PPC_REL24 relocation at 0x0f9f0148 for symbol `_restgpr_29_x' out of range
On Sat, Apr 30, 2011 at 12:00:41PM +0200, Mike Hommey wrote:
> On Thu, Apr 28, 2011 at 02:17:15PM +0200, Gabriel Paubert wrote:
> > On Thu, Apr 28, 2011 at 12:10:54PM +0200, Mike Hommey wrote:
> > > On Thu, Apr 28, 2011 at 12:04:42PM +0200, Mike Hommey wrote:
> > > > Let me write it again:
> > > > - The R_PPC_REL24 relocations are all over libxul.so on objects that are
> > > > built -fPIC.
> > > > - libcrmf.a is also linked into libxul.so, and it also contains
> > > > R_PPC_REL24 relocations, but all the objects it contains are built
> > > > -fPIC.
> > >
> > > And this is a -Os bug, apparently. Building with -O2 doesn't seem to
> > > yield these relocations.
> >
> > That's because the out-of-line prologue/epilogue register save and
> > restore functions are only used at -Os (they save size).
> >
> > Now I believe, but don't quote me on that, that the linker
> > should insert a copy of these functions in every shared library
> > since these functions have non standard linkage and probably
> > would not survive crossing shared library boundaries.
> >
> > I can see a bug if the shared library text size is above
> > 32M or so (needs several copies of these functions), but
> > I don't think the libraries are that big.
>
> The linker actually normally does that, because it compiles with -lgcc,
> which will link libgcc.a, which contains these functions.
>
> However, for some reason, in libxul.so case, gcc uses -shared-libgcc,
> which I fail to see where it collects it from (thanks KiBi for the
> verbose build, see below).
>
> OTOH, I still can't reproduce with a simple test case. The linker still
> seems to do the right thing. Even if I use the same build flags.
> I really don't know what makes the libxul.so case so special. Its size?
So, the problem is its compile line, containing
-lstartup-notification-1, and has nothing to do with -shared-libgcc.
It looks like startup-notification was built with a broken toolchain in
2009 (will ask for a binNMU), and exported the _rest* symbols that
libgcc.a also contains. As -lstartup-notification-1 appears before -lgcc
on the link line, ld wrongly picks the versions in
startup-notification-1.
So it looks to me like there were and are several problems:
- The original problem that made startup-notification export these
symbols, that is gone.
- gcc, that doesn't mark _rest* symbols as hidden in object files (they
are in libgcc.a)
I guess fixing the latter would either force ld to use the libgcc.a
symbols or fail to link with the startup-notification symbols.
Mike
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