Re: [patch] Fix ELF stale reference [Re: [patch] .gdb_index: Do not crash on NOBITS]

[Doug Evans <dje@google.com>]

On Thu, Sep 9, 2010 at 2:05 AM, Jan Kratochvil
<jan.kratochvil@redhat.com> wrote:
>
> gdb/
> 2010-09-09  Jan Kratochvil  <jan.kratochvil@redhat.com>
>
>        Fix stale memory references.
>        * elfread.c: Include libbfd.h.
>        (elf_symfile_read): Replace xmalloc by bfd_alloc, drop xfree, new
>        comment.
>
> --- a/gdb/elfread.c
> +++ b/gdb/elfread.c
> @@ -37,6 +37,7 @@
>  #include "complaints.h"
>  #include "demangle.h"
>  #include "psympriv.h"
> +#include "libbfd.h"

Apologies for nitpicking but this raises an issue I'd like to understand better.
I thought libbfd.h was an internal bfd header.
[I know I've wanted to use it at least once and been told "No." :-)]

>
>  extern void _initialize_elfread (void);
>
> @@ -792,8 +793,14 @@ elf_symfile_read (struct objfile *objfile, int symfile_flags)
>
>   if (storage_needed > 0)
>     {
> -      dyn_symbol_table = (asymbol **) xmalloc (storage_needed);
> -      make_cleanup (xfree, dyn_symbol_table);
> +      /* Memory gets permanently referenced from ABFD after
> +        bfd_get_synthetic_symtab so it must not get freed before ABFD gets.
> +        It happens only in the case when elf_slurp_reloc_table sees
> +        asection->relocation NULL.  Determining which section is asection is
> +        done by _bfd_elf_get_synthetic_symtab which is all a bfd
> +        implementation detail, though.  */
> +
> +      dyn_symbol_table = bfd_alloc (abfd, storage_needed);
>       dynsymcount = bfd_canonicalize_dynamic_symtab (objfile->obfd,
>                                                     dyn_symbol_table);
>