Re: PR22458, failure to choose a matching ELF target

["H.J. Lu" <hjl dot tools at gmail dot com>]

On Wed, May 16, 2018 at 5:15 AM, Alan Modra <amodra@gmail.com> wrote:
> https://sourceware.org/ml/binutils/2013-05/msg00271.html was supposed
> to banish "file format is ambiguous" errors for ELF.  It didn't,
> because the code supposedly detecting formats that implement
> match_priority didn't work.  That was due to not placing all matching
> targets into the vector of matching targets.  ELF objects should all
> match the generic ELF target (priority 2), plus one or more machine
> specific targets (priority 1), and perhaps a single machine specific
> target with OS/ABI set (priority 0, best match).  So the armel object
> in the testcase actually matches elf32-littlearm,
> elf32-littlearm-symbian, and elf32-littlearm-vxworks (all priority 1),
> and elf32-little (priority 2).  As the PR reported, elf32-little
> wasn't seen as matching.  Fixing that part of the problem wasn't too
> difficult but matching the generic ELF target as well as the ARM ELF
> targets resulted in ARM testsuite failures.
>
> These proved to be the annoying reordering of stubs that occurs from
> time to time due to the stub names containing the section id.
> Matching another target causes more sections to be created in
> elf_object_p.  If section ids change, stub names change, which results
> in different hashing and can therefore result in different hash table
> traversal and stub creation order.  That particular problem is fixed
> by resetting section_id to the initial state before attempting each
> target match, and taking a snapshot of its value after a successful
> match.
>
>         PR 22458
>         * format.c (struct bfd_preserve): Add section_id.
>         (bfd_preserve_save, bfd_preserve_restore): Save and restore
>         _bfd_section_id.
>         (bfd_reinit): Set _bfd_section_id.
>         (bfd_check_format_matches): Put all matches of any priority into
>         matching_vector.  Save initial section id and start each attempted
>         match at that section id.
>         * libbfd-in.h (_bfd_section_id): Declare.
>         * section.c (_bfd_section_id): Rename from section_id and make
>         global.  Adjust uses.
>         (bfd_get_next_section_id): Delete.
>         * elf64-ppc.c (ppc64_elf_setup_section_lists): Replace use of
>         bfd_get_section_id with _bfd_section_id.
>         * libbfd.h: Regenerate.
>         * bfd-in2.h: Regenerate.
>

> diff --git a/bfd/libbfd-in.h b/bfd/libbfd-in.h
> index 0c80f4d598..d8b445f894 100644
> --- a/bfd/libbfd-in.h
> +++ b/bfd/libbfd-in.h
> @@ -53,6 +53,9 @@ struct section_hash_entry
>    asection section;
>  };
>
> +/* Unique section id.  */
> +extern unsigned int _bfd_section_id;
> +

Should it be marked as hidden?

-- 
H.J.