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Re: [RFC] Hide autogenerated symbols when linking shared libraries
- From: Nick Clifton <nickc at redhat dot com>
- To: Yuri Gribov <tetra2005 at gmail dot com>
- Cc: binutils at sourceware dot org
- Date: Thu, 3 May 2018 11:03:24 +0100
- Subject: Re: [RFC] Hide autogenerated symbols when linking shared libraries
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- References: <CAJOtW+4ifhHp4R3z6pfD2bSaSOjh8hb3LafxFDdR8pbc3RysOg@mail.gmail.com> <2858374c-3652-add8-c785-6b409b99eee3@redhat.com> <CAJOtW+4+NpSq1aBVmsOPg=AFzFh+ddkFp5Nv==gdPHgeQQRO8g@mail.gmail.com>
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.
> 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.
>> 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.
Cheers
Nick