[1/3] Move core_bfd to program space

  From: Tom Tromey <tromey@redhat.com>

This moves the core_bfd global to be a field of the program space.  It
then replaces core_bfd with a macro to avoid a massive patch -- the
same approach taken for various other program space fields.

This is a basic transformation for multi-target work.

yyyy-mm-dd  Tom Tromey  <tromey@redhat.com>
	    Pedro Alves  <tromey@redhat.com>

	* corefile.c (core_bfd): Remove.
	* gdbcore.h (core_bfd): Now a macro.
	* progspace.h (struct program_space) <cbfd>: New field.
---
 gdb/corefile.c  | 4 ----
 gdb/gdbcore.h   | 2 +-
 gdb/progspace.h | 3 +++
 3 files changed, 4 insertions(+), 5 deletions(-)
  

>>>>> "Pedro" == Pedro Alves <palves@redhat.com> writes:

Pedro> This moves the core_bfd global to be a field of the program space.  It
Pedro> then replaces core_bfd with a macro to avoid a massive patch -- the
Pedro> same approach taken for various other program space fields.

I am curious to know whether you would want to remove this macro in the
future.  I don't mean that you should do it -- just more a question of
what direction to go.  There are other macros like this too:
symfile_objfile, object_files, exec_bfd, ...

Also, I can't remember why I moved core_bfd to the progspace.  Would it
be better to have it just be a member of the target?  Or maybe in your
design these end up being basically equivalent, because core targets are
inherently single-process?

Tom
  

On 05/04/2018 04:41 PM, Tom Tromey wrote:
>>>>>> "Pedro" == Pedro Alves <palves@redhat.com> writes:
> 
> Pedro> This moves the core_bfd global to be a field of the program space.  It
> Pedro> then replaces core_bfd with a macro to avoid a massive patch -- the
> Pedro> same approach taken for various other program space fields.
> 
> I am curious to know whether you would want to remove this macro in the
> future.  I don't mean that you should do it -- just more a question of
> what direction to go.  There are other macros like this too:
> symfile_objfile, object_files, exec_bfd, ...

Yeah, I have no plans to do that myself, but I wouldn't oppose
changing it.

> Also, I can't remember why I moved core_bfd to the progspace.  Would it
> be better to have it just be a member of the target?  Or maybe in your
> design these end up being basically equivalent, because core targets are
> inherently single-process?
Yeah, I guess program space just felt natural given exec_bfd is there
too.  Not sure about putting it in the target.  Making it a data field of
target_ops I think would be odd.  It might work if we replaced it
with something like (in the multi-target branch):

bfd *
core_bfd ()
{
  if (core_target *core 
      = dynamic_cast<core_target *> 
          (current_inferior ()->process_target ()))
    return core->core_bfd;
  return nullptr;
}

though that's a bit smelly, and when I see dynamic_cast
I can't avoid thinking about how inefficient it is.  :-)

Alternatively, we could make core_bfd() a virtual method of
target_ops instead, that has most targets except the
core_target target return NULL.

Not sure.  Putting it in program space just seemed like an
easy and OK thing to do.

Thanks,
Pedro Alves
  

>>>>> "Pedro" == Pedro Alves <palves@redhat.com> writes:

>> I am curious to know whether you would want to remove this macro in the
>> future.  I don't mean that you should do it -- just more a question of
>> what direction to go.  There are other macros like this too:
>> symfile_objfile, object_files, exec_bfd, ...

Pedro> Yeah, I have no plans to do that myself, but I wouldn't oppose
Pedro> changing it.

Thanks.

Pedro> Yeah, I guess program space just felt natural given exec_bfd is there
Pedro> too.

That makes sense, thanks.

Tom