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Re: [PATCH 3/5] remove deleted BFDs from the archive cache
On Thu, Aug 16, 2012 at 10:02 AM, Tom Tromey <tromey@redhat.com> wrote:
> HJ> Your checkin destroys binutils:
> HJ> http://sourceware.org/bugzilla/show_bug.cgi?id=14475
> HJ> Can you fix it?
>
> Sorry about that. I see now that I will need a more clever plan to
> destroy binutils.
>
> I debugged it. The immediate problem is that
> _bfd_compute_and_write_armap calls bfd_free_cached_info
> (aka _bfd_free_cached_info). This then does:
>
> objalloc_free ((struct objalloc *) abfd->memory);
>
> Whoops, this also frees the areltdata.
>
> So, I have two possible fixes for it.
>
> I've appended the first possible fix. It changes _bfd_free_cached_info
> not to free all the memory attached to the BFD.
>
> A couple notes here.
>
> First, it seems very wrong to me to clear usrdata in this function. I
> didn't touch this; since presumably clients may be relying on this
> clearing in a subtle way (if they allocate the usrdata on the BFD
> objalloc, which is perhaps the only sensible approach anyhow). But, I
> think that if the appended patch goes in then this line should be
> removed in a follow-up.
>
> Second, the check in _bfd_delete_bfd is perhaps ugly. Maybe
> bfd_hash_table_free should do this check instead. Let me know what you
> think.
>
> I rebuilt ld and binutils with this patch. Additionally, I hacked the
> Makefiles to link all the programs with -lmcheck. Then I ran the ld and
> binutils test suites. There were no regressions. I also examined one
> particular case from ar.exp using valgrind -- I could reproduce the
> problem before the patch, but not after.
>
>
> Another possible fix for this bug would be to allocate the areltdata
> using malloc. That way it would be immune to the objalloc_free call.
> This would require a few more tweaks, like properly freeing it in
> _bfd_delete_bfd, etc.
>
> I'm happy to make and test this change if you think it would be better.
>
> Tom
>
> 2012-08-16 Tom Tromey <tromey@redhat.com>
>
> * opncls.c (_bfd_delete_bfd): Check to see if section htab is
> already freed.
> (_bfd_free_cached_info): Don't free the objalloc.
>
> Index: opncls.c
> ===================================================================
> RCS file: /cvs/src/src/bfd/opncls.c,v
> retrieving revision 1.72
> diff -u -r1.72 opncls.c
> --- opncls.c 9 Aug 2012 06:25:53 -0000 1.72
> +++ opncls.c 16 Aug 2012 16:57:36 -0000
> @@ -132,14 +132,15 @@
> {
> if (abfd->memory)
> {
> - bfd_hash_table_free (&abfd->section_htab);
> + if (abfd->section_htab.memory != NULL)
> + bfd_hash_table_free (&abfd->section_htab);
> objalloc_free ((struct objalloc *) abfd->memory);
> }
>
> free (abfd);
> }
>
> -/* Free objalloc memory. */
> +/* Free some information cached in the BFD. */
>
> bfd_boolean
> _bfd_free_cached_info (bfd *abfd)
> @@ -147,14 +148,12 @@
> if (abfd->memory)
> {
> bfd_hash_table_free (&abfd->section_htab);
> - objalloc_free ((struct objalloc *) abfd->memory);
>
> abfd->sections = NULL;
> abfd->section_last = NULL;
> abfd->outsymbols = NULL;
> abfd->tdata.any = NULL;
> abfd->usrdata = NULL;
> - abfd->memory = NULL;
> }
>
> return TRUE;
I think it is better to use malloc on areltdata so that
we can call objalloc_free to keep memory usage down.
Thanks.
--
H.J.