Re: PATCH] PR target/65612: Multiversioning doesn't work with DSO nor PIE

["H.J. Lu" <hjl.tools@gmail.com>]

On Fri, Apr 17, 2015 at 4:37 AM, Jakub Jelinek <jakub@redhat.com> wrote:
> On Fri, Apr 17, 2015 at 01:04:20PM +0200, Uros Bizjak wrote:
>> On Fri, Apr 17, 2015 at 12:36 PM, H.J. Lu <hjl.tools@gmail.com> wrote:
>>
>> >>>>> I can confirm that the most current patch bootstraps on
>> >>>>> x86_64-apple-darwin14 and that all of the new tests show up as
>> >>>>> unsupported in the test suite.
>> >>>>>          Jack
>> >>>>
>> >>>> I am re-posting this patch.  OK for trunk?
>> >>>
>> >>> If Jack is happy, I’m happy.  :-)  That leaves the x86 people to comment on it.
>> >>
>> >> What about Solaris?
>> >>
>> >> Uros.
>> >
>> > There are
>>
>> [...]
>>
>> Assuming Jakub is OK with the patch, let's go ahead with it.
>>
>> OK for mainline.
>
> I don't like it.  Nonshared libgcc is libgcc.a, period.  No sense in
> creating yet another library for that.
> So, IMHO beyond making the __cpu* entrypoints compat symbols only (@ instead
> of @@ symbol versions) the right fix is simply tweak init_gcc_spec, so that
> static_name is always linked in, in the switch combinations that it isn't
> right now of course after shared_name rather than before that.
> I thought we've fixed that years ago...
>

We never pass -lgcc to linker when building C++ DSO:

 /usr/libexec/gcc/x86_64-redhat-linux/4.9.2/collect2 -plugin
/usr/libexec/gcc/x86_64-redhat-linux/4.9.2/liblto_plugin.so
-plugin-opt=/usr/libexec/gcc/x86_64-redhat-linux/4.9.2/lto-wrapper
-plugin-opt=-fresolution=/tmp/ccZC7iqy.res
-plugin-opt=-pass-through=-lgcc_s -plugin-opt=-pass-through=-lc
-plugin-opt=-pass-through=-lgcc_s --build-id --no-add-needed
--eh-frame-hdr --hash-style=gnu -m elf_x86_64 -shared
/usr/lib/gcc/x86_64-redhat-linux/4.9.2/../../../../lib64/crti.o
/usr/lib/gcc/x86_64-redhat-linux/4.9.2/crtbeginS.o
-L/usr/lib/gcc/x86_64-redhat-linux/4.9.2
-L/usr/lib/gcc/x86_64-redhat-linux/4.9.2/../../../../lib64
-L/lib/../lib64 -L/usr/lib/../lib64
-L/usr/lib/gcc/x86_64-redhat-linux/4.9.2/../../.. x.o -lstdc++ -lm
-lgcc_s -lc -lgcc_s /usr/lib/gcc/x86_64-redhat-linux/4.9.2/crtendS.o
/usr/lib/gcc/x86_64-redhat-linux/4.9.2/../../../../lib64/crtn.o
[hjl@gnu-32 tmp]$

That is why libgcc_nonshared.a is needed.


-- 
H.J.