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[Bug ld/13177] garbage collector retains zombie references to external l

From: cvs-commit at gcc dot gnu.org
Subject: [Bug ld/13177] garbage collector retains zombie references to external libraries
Date: Wed, 18 Jan 2017 18:32:26 +0000


--- Comment #9 from cvs-commit at gcc dot gnu.org <cvs-commit at gcc dot 
gnu.org> ---
The master branch has been updated by Maciej W. Rozycki <address@hidden>:


commit 81ff47b3a54633819fac4d973e34f1ff0c65606e
Author: Maciej W. Rozycki <address@hidden>
Date:   Mon Jan 16 22:10:57 2017 +0000

    PR ld/20828: Fix linker script symbols wrongly forced local with section GC

    Fix a generic ELF linker regression introduced with a chain of changes
    made to unused input section garbage collection:

    - commit 1a766c6843ce ("Also hide symbols without PLT nor GOT

    - commit 1d5316ab67e1 ("PR ld/13177: garbage collector retains zombie
      references to external libraries"),

    - commit 6673f753c019 ("Fix PR 12772, garbage collection of dynamic
      syms"), <https://sourceware.org/ml/binutils/2011-12/msg00077.html>,

    causing the garbage collection of unused symbols present in a DSO
    involved in a link to make identically named symbols ordinarily defined
    (i.e. not hidden or PROVIDEd) by a linker script local, even though the
    latter symbols are supposed to be global as if no DSO defined them as

    This is because linker script assignments are processed very late as
    `lang_process' proceeds, down in the call to `ldemul_before_allocation',
    which is made after the call to `lang_gc_sections' to do input section
    garbage collecting.  Consequently if unused, then any such DSO-defined
    symbol has already been garbage-collected and internally marked local.
    It would ordinarily be removed from dynamic symbol table output, however
    a linker script assignment correctly replaces its original definition
    with the new one and enters it into the dynamic symbol table produced as
    it is supposed to be exported.  The original local marking is however
    retained making the symbol local in the dynamic symbol table and
    therefore not available externally.  This also causes a sorting problem
    with the MIPS target, which does not expect non-section local dynamic
    symbols to be output and produces an invalid binary.

    Fix the problem then, by removing the `forced_local' marking for the
    offending case and add suitable test cases.  First to verify that unused
    symbols ordinarily defined with linker script assignments remain
    exported in the context of input section garbage collection whether or
    not a DSO defining identically named symbols is present in the link.
    Second that a linker version script still correctly retains or removes
    such symbols as requested.

        PR ld/20828
        * elflink.c (bfd_elf_record_link_assignment): Clear any
        `forced_local' marking for DSO symbols that are not being

        PR ld/20828
        * testsuite/ld-elf/pr20828-1.sd: New test.
        * testsuite/ld-elf/pr20828-2a.sd: New test.
        * testsuite/ld-elf/pr20828-2b.sd: New test.
        * testsuite/ld-elf/pr20828.ld: New test linker script.
        * testsuite/ld-elf/pr20828.ver: New test version script.
        * testsuite/ld-elf/pr20828.s: New test source.
        * testsuite/ld-elf/shared.exp: Run the new test.

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