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Re: [PATCH 3/5] remove deleted BFDs from the archive cache
On Fri, Aug 17, 2012 at 9:09 AM, Tom Tromey <firstname.lastname@example.org> wrote:
> Alan> Tom said he'd look into fixing the leak this causes, so I'm happy
> Alan> to leave that to him. :)
> Here's the patch.
> I think it would be good for someone to double check it.
> I wrote this patch by searching for all the places that could allocate
> an areltdata and changing them to use bfd_zmalloc.
> Then I examined all the users of bfd->arelt_data and all callers of
> bfd_read_ar_hdr (and _bfd_read_ar_hdr) to see how the data was used.
> This revealed a number of spots that used bfd_release to free this data.
> Finally, I added a free to _bfd_delete_bfd.
> I once again built ld and all the binutils programs with -lmcheck, and
> then ran the test suites. These all passed. I also ran a single 'ar'
> test (one that was failing yesterday) plus the new 'bfdtest1' test under
> valgrind. These were also clean.
> I found a few oddities in BFD while working on this patch:
> * _bfd_get_elt_at_filepos can release new_areldata but still leave a
> stale pointer in n_nfd->arelt_data. I fixed this. I am not sure if
> this can ever result in a bug, but I think paranoia is preferable.
> * bfd_slurp_bsd_armap_f2 leaks 'mapdata' before the patch -- it frees it
> on the error path but not on the normal path. I fixed this.
> * _bfd_xcoff_read_ar_hdr currently allocates 'ret' with bfd_alloc. I
> think it should clear it instead; I did this.
> Also, this function already assumes 'ret' is malloced, which is a
> latent bug.
> One final note on arelt_data: right now it is a void* in the BFD. It
> seems to me that it would be just as opaque, and more type-safe, to
> change the structure name to 'struct bfd_areltdata', then use this name
> in the BFD -- but leave the struct type incomplete so that library
> clients can't dereference it.
> 2012-08-17 Tom Tromey <email@example.com>
> * vms-lib.c (_bfd_vms_lib_get_module): Use bfd_zmalloc for
> * opncls.c (_bfd_delete_bfd): Free arelt_data.
> * mach-o.c (bfd_mach_o_fat_member_init): Use bfd_zmalloc for
> * ecoff.c (_bfd_ecoff_slurp_armap): Use free for mapdata.
> * coff-rs6000.c (_bfd_xcoff_read_ar_hdr): Use bfd_zmalloc for
> (xcoff_write_archive_contents_old): Likewise.
> (xcoff_write_archive_contents_big): Likewise.
> * archive64.c (bfd_elf64_archive_slurp_armap): Use free for
> * archive.c (_bfd_generic_read_ar_hdr_mag): Use bfd_zmalloc and
> free for areltdata.
> (_bfd_get_elt_at_filepos): Likewise. Clear n_nfd->arelt_data on
> (do_slurp_bsd_armap): Use bfd_zmalloc and free for areltdata.
> (do_slurp_coff_armap): Likewise.
> (_bfd_slurp_extended_name_table): Likewise.
> (bfd_slurp_bsd_armap_f2): Likewise. Don't leak 'mapdata'.
I am not sure if we want to use bfd_zmalloc for all areltdata. We
use bfd_ar_hdr_from_filesystem since we can't use member
objalloc nor archive objalloc. In all other places, it is OK to
use archive objalloc for areltdata.
Do you have a testcase to show there is a problem?