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[PATCH] PR ld/18720: Properly merge hidden versioned symbol

H.J. Lu hjl.tools@gmail.com
Mon Feb 1 20:47:00 GMT 2016 
On Mon, Feb 1, 2016 at 12:22 PM, Mike Frysinger <vapier@gentoo.org> wrote:
> On 01 Aug 2015 07:07, H.J. Lu wrote:
>> On Sun, Jul 26, 2015 at 03:15:50PM -0700, H.J. Lu wrote:
>> > The non-default versioned symbol can only be merged with the versioned
>> > symbol with the same symbol version.  _bfd_elf_merge_symbol should
>> > check the symbol version before merging the new non-default versioned
>> > symbol with the existing symbol.  _bfd_elf_link_hash_copy_indirect can't
>> > copy any references to the non-default versioned symbol.   We need to
>> > bind a symbol locally when linking executable if it is locally defined,
>> > non-default versioned, not referenced by shared library and not exported.
>> > ---
>> > bfd/
>> >
>> >     PR ld/18720
>> >     * elf-bfd.h (elf_link_hash_entry): Add nondeflt_version.
>> >     * elflink.c (_bfd_elf_merge_symbol): Add a parameter to indicate
>> >     if the new symbol matches the existing one.  The new non-default
>> >     versioned symbol symbol matches the existing symbol if they have
>> >     the same symbol version. Update the existing symbol only if they
>> >     match.
>> >     (_bfd_elf_add_default_symbol): Update call to
>> >     _bfd_elf_merge_symbol.
>> >     (elf_link_add_object_symbols): Override a definition only if the
>> >     new symbol matches the existing one.
>> >     (_bfd_elf_link_hash_copy_indirect): Don't copy any references to
>> >     the non-default versioned symbol.
>> >     (elf_link_output_extsym): Bind a symbol locally when linking
>> >     executable if it is locally defined, non-default versioned, not
>> >     referenced by shared library and not exported.
>>
>> Here is the upated patch which uses the existing "hidden" field in
>> elf_link_hash_entry.  Any objections, comments?
>
> this breaks asan.  simple test case:
> $ echo 'main() { fork(); }' > test.c
> $ gcc -fsanitize=address -c test.c
> $ gcc -fsanitize=address test.o
> ld: /usr/lib/gcc/x86_64-pc-linux-gnu/5.3.0/libasan.so: undefined reference to symbol 'fork@GLIBC_2.2.5'
> /lib64/libpthread.so.0: error adding symbols: DSO missing from command line
> collect2: error: ld returned 1 exit status
>
> i'm guessing this will also break any library that links against pthread
> but the main app itself doesn't.
> -mike

Please open a binutils bug.

Thanks.

-- 
H.J.
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