Linking against libgcc.a on GNU/Linux

Linking against libgcc.a on GNU/Linux

[Florian Weimer]

Would it be possible to turn libgcc_s.so into a linker script that links
against libgcc.a and libgcc_s.so.1, and teach g++ not to link against
libgcc.a explicitly anymore?

I'm suggesting this because libtool uses -nostdlib when linking shared
objects in C++ mode, and does not link against -lgcc, only -lgcc_s.
This causes subtle problems if GCC generates code that actually needs
libgcc.a, particularly if the main program uses the same symbols and
gets the hidden definitions from libgcc.a.

As far as I can tell, previous attempts to dissuade libtool from using
-nostdlib have failed.  It is also difficult to change libtool as it is
deployed in package sources.  It seems to me that the GCC workaround
could be rolled out quite seamlessly.

Thanks,
Florian

Re: Linking against libgcc.a on GNU/Linux

[Joseph Myers]

On Wed, 13 Mar 2019, Florian Weimer wrote:

> Would it be possible to turn libgcc_s.so into a linker script that links
> against libgcc.a and libgcc_s.so.1, and teach g++ not to link against
> libgcc.a explicitly anymore?

It is already a linker script on platforms using t-slibgcc-libgcc in 
libgcc/config.host.

-- 
Joseph S. Myers
joseph@codesourcery.com

Re: Linking against libgcc.a on GNU/Linux

[Florian Weimer]

* Joseph Myers:

> On Wed, 13 Mar 2019, Florian Weimer wrote:
>
>> Would it be possible to turn libgcc_s.so into a linker script that links
>> against libgcc.a and libgcc_s.so.1, and teach g++ not to link against
>> libgcc.a explicitly anymore?
>
> It is already a linker script on platforms using t-slibgcc-libgcc in 
> libgcc/config.host.

Hmm.  I assume this means that x86-64 and i386 should use this approach,
but they currently do not (GCC 8/9 in Fedora):

  <https://gcc.gnu.org/bugzilla/show_bug.cgi?id=88805#c5>

Thanks,
Florian

Re: Linking against libgcc.a on GNU/Linux

[Florian Weimer]

* Florian Weimer:

> * Joseph Myers:
>
>> On Wed, 13 Mar 2019, Florian Weimer wrote:
>>
>>> Would it be possible to turn libgcc_s.so into a linker script that links
>>> against libgcc.a and libgcc_s.so.1, and teach g++ not to link against
>>> libgcc.a explicitly anymore?
>>
>> It is already a linker script on platforms using t-slibgcc-libgcc in 
>> libgcc/config.host.
>
> Hmm.  I assume this means that x86-64 and i386 should use this approach,
> but they currently do not (GCC 8/9 in Fedora):
>
>   <https://gcc.gnu.org/bugzilla/show_bug.cgi?id=88805#c5>

Never mind, Jakub identified this as a downstream bug.

Thanks,
Florian