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Re: [RFA] crash while re-reading symbols from objfile on ppc-aix.

> Joel> The critical difference between
> Joel> a platform such as x86_64-linuxe where it works, and ppc-aix,
> Joel> where it doesn't lies in the fact that bfd-data sharing is not
> Joel> activated on ppc-aix, and as a result, the per-bfd data gets
> Joel> allocated on the objfile's obstack instead of in the bfd objalloc:
> I'm curious to know why it doesn't share.

I will try looking it up tomorrow if I have a moment. I just assumed
at the time that this was related to the object format not having been
updated to support sharing. Although, quoting the relevant code again:

    | /* If the object requires gdb to do relocations, we simply fall
    |    back to not sharing data across users.  These cases are rare
    |    enough that this seems reasonable.  */
    | if (abfd != NULL && !gdb_bfd_requires_relocations (abfd))
    |   {
    |     storage = bfd_zalloc (abfd, sizeof (struct objfile_per_bfd_storage));
    |     set_bfd_data (abfd, objfiles_bfd_data, storage);
    |   }
    | else
    |   storage = OBSTACK_ZALLOC (&objfile->objfile_obstack,
    |                             struct objfile_per_bfd_storage);

.. the important piece seems to be that gdb_bfd_requires_relocations
needs to be false. gdb_bfd_requires_relocations iterates over
all sections looking for SEC_RELOC:

        if ((sect->flags & SEC_RELOC) != 0)
            gdata->needs_relocations = 1;

And looking at the .text section for our binary:

  0 .text         00000480  10000200  10000200  00000200  2**7
                  CONTENTS, ALLOC, LOAD, RELOC, CODE

Is that enough to explain the non-sharing?

> Joel>         * symfile.c (reread_symbols): Move call to set_objfile_per_bfd
> Joel>         after re-initialization of OBJFILE's obstack.
> Joel> Tested on x86_64-linux, no regression. Also tested on ppc-aix using
> Joel> AdaCore's testsuite (expect hangs at the end of the test, on ppc-aix,
> Joel> so I can't collect any result).
> Joel> Ok to commit?
> Yes, definitely.  Thanks.

Thanks, Tom. I will commit tomorrow.


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