[RFC] Hide autogenerated symbols when linking shared libraries

[Yuri Gribov]

On Thu, May 3, 2018 at 11:03 AM, Nick Clifton <nickc@redhat.com> wrote:
> Hi Yuri,
>
>> Ok, fair enough.  Still let me point out that presently these symbols
>> pollute binary interfaces of any shared library compiled with default
>> flags by GNU/LLVM tools.
>
> Is it really a big problem though ?  I would imagine that the amount of
> space used by these symbols is trivial compared to the size of the rest
> of any typical shared library.

Definitely not a big problem, more of a cosmetic issue.

>> Do you have any particular uses in mind?  I tried grepping glibc,
>> binutils-gdb or libgcc for bss_start but couldn't find anything which
>> would justify them having default visibility...
>
> Not really - I was just speaking in generalities.  It may well turn out
> that for, say x86_64 Linux based systems, these symbols are not needed.
> But I would be very wary of removing them without a lot of testing first
> as this is exactly the kind of thing that can break systems in unexpected,
> and unanticipated ways.

Sure, no arguing on that one.

>>> PS.  You can always create your own linker script which does not define
>>> these symbols...
>>
>> Thanks but I'm more worried about distros (I came across them while
>> investigating redundant symbols exported by Debian packages).  Asking
>> every package maintainer to use -Wl,--version-script won't scale very
>> well...
>
> True. :-)  Although some distros due do use special packages that provide
> the default linker command line options when building applications (and
> libraries).  EG Fedora's redhar-rpm-config package.  So you could make a
> change only in this package and have it affect most apps.

Nice, will keep that in mind!

-Y