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

[Mike Frysinger <vapier at gentoo dot org>]

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

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