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Re: [RFA] Remove target_section.bfd
- From: Doug Evans <dje at google dot com>
- To: Tom Tromey <tromey at redhat dot com>
- Cc: gdb-patches <gdb-patches at sourceware dot org>
- Date: Tue, 16 Jul 2013 11:27:27 -0700
- Subject: Re: [RFA] Remove target_section.bfd
- References: <yjt2ip0bbg2u dot fsf at ruffy dot mtv dot corp dot google dot com> <87oba2jruh dot fsf at fleche dot redhat dot com>
On Tue, Jul 16, 2013 at 11:13 AM, Tom Tromey <tromey@redhat.com> wrote:
>>>>>> "Doug" == Doug Evans <dje@google.com> writes:
>
> Doug> While reviewing the remove-symbol-file patchset I came across
> Doug> target_section.bfd.
> Doug> Unnecessarily storing copies of things can lead to confusion and bugs.
> Doug> This patch isn't intended to be a space savings, simply a cleanup.
>
> I think it is a nice cleanup. Thanks.
>
> Doug> We already liberally reference bfd_section.owner, so I have no problem
> Doug> with adding more references here.
>
> The only danger is that some BFD sections do not have an owner. For
> example, this is true of the absolute section, which is shared by all
> BFDs, something I found out the hard way. Now, I think this is wrong of
> BFD to do, but fixing it seemed hard.
Righto. I've taken those into account (or at least tried to ...).
[There's a FIXME in bfd for this btw. Don't know if it'll ever get
implemented.]
> Sometimes it is safe to use the section owner nevertheless; for instance
> if you're sure that an ownerless section will never be used in this
> context.
>
> I don't know whether this applies in this case. Perhaps not because
> build_section_table uses bfd_map_over_sections, and I think that doesn't
> include the ownerless sections.
I looked at this.
bfd_map_over_sections does this:
void
bfd_map_over_sections (bfd *abfd,
void (*operation) (bfd *, asection *, void *),
void *user_storage)
{
asection *sect;
unsigned int i = 0;
for (sect = abfd->sections; sect != NULL; i++, sect = sect->next)
(*operation) (abfd, sect, user_storage);
if (i != abfd->section_count) /* Debugging */
abort ();
}
That can't work for "global" sections (abs,com,und, etc.).
And that's the only way the sections we care about here get added in
gdb (AFAICT).
> Doug> [Ideally bfd would provide accessor functions/macros for struct
> Doug> bfd_section, but none exist at all, and I'm not inclined to add all of
> Doug> them just for this patch.]
>
> I went through that same thought process.
>
> Doug> Ok to check in?
>
> I think it is fine; but if you could verify about bfd_map_over_sections,
> that would be good.
>
> Tom