<OS specific> symbols

<OS specific> symbols

[Tom Kacvinsky]

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I ran across an interesting third party tool that has this interesting
facet:

vapkay@vadcpctlbld4 ~ $ readelf -Wa /opt/bin/fubar | grep
_ZGVNSt7collateIwE2idE



0000000000921d28  0000003200000006 R_X86_64_GLOB_DAT      0000000000939cf0
_ZGVNSt7collateIwE2idE + 0

    50: 0000000000939cf0     8 OBJECT  <OS specific>: 10 DEFAULT   29
_ZGVNSt7collateIwE2idE


That is definitely a C++ symbol, but libstdc++.so was not linked
dynamically.  I am wanting to know how one would get an <OS specific>
symbol, and if there is a way of working around this at run time.  This
tool works fine on CenTOS 7 but not on CentOS 5.


Thanks,


Tom

Re: <OS specific> symbols

[Andreas Schwab]

On Mär 18 2023, Tom Kacvinsky via Binutils wrote:

>     50: 0000000000939cf0     8 OBJECT  <OS specific>: 10 DEFAULT   29
> _ZGVNSt7collateIwE2idE

10 is STB_GNU_UNIQUE.

> That is definitely a C++ symbol, but libstdc++.so was not linked
> dynamically.  I am wanting to know how one would get an <OS specific>
> symbol, and if there is a way of working around this at run time.  This
> tool works fine on CenTOS 7 but not on CentOS 5.

Looks like the CentOS 5 toolchain does not know about GNU_UNIQUE
symbols.

-- 
Andreas Schwab, schwab@linux-m68k.org
GPG Key fingerprint = 7578 EB47 D4E5 4D69 2510  2552 DF73 E780 A9DA AEC1
"And now for something completely different."

Re: <OS specific> symbols

[Tom Kacvinsky]

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Hi Andreas,

On Sat, Mar 18, 2023 at 10:57 AM Andreas Schwab <schwab@linux-m68k.org>
wrote:

> On Mär 18 2023, Tom Kacvinsky via Binutils wrote:
>
> >     50: 0000000000939cf0     8 OBJECT  <OS specific>: 10 DEFAULT   29
> > _ZGVNSt7collateIwE2idE
>
> 10 is STB_GNU_UNIQUE.
>
> > That is definitely a C++ symbol, but libstdc++.so was not linked
> > dynamically.  I am wanting to know how one would get an <OS specific>
> > symbol, and if there is a way of working around this at run time.  This
> > tool works fine on CenTOS 7 but not on CentOS 5.
>
> Looks like the CentOS 5 toolchain does not know about GNU_UNIQUE
> symbols.
>

It turns out support for STB_GNU_UNIQUE  was implemented in glibc 2.11.
CentOS 7 is glibc 2.17 based (which is why the tool worked there) but the
glibc version on CentOS 5 is 2.5.  Because of that, I'm out of luck.

Thanks for pointing me in the right direction.

Tom