Re: gdbarch: ABFD no longer available at gdbarch_update_p time

[Andrew Cagney <ac131313@cygnus.com>]

> I'm trying to add a ``set mips abi'' as we discussed earlier.  I can't find
> a way to do it.  The way CRIS does this sort of thing is patently wrong (for
> MIPS at least, if not for CRIS also):

Interesting, especially given the CRIS target implements it correctly :-)

>       /* Update the current architecture, if needed.  */
>       gdbarch_info_init (&info);
>       if (!gdbarch_update_p (info))
>         internal_error (__FILE__, __LINE__, "cris_gdbarch_update: failed to update architecture.");


The sequence is:

- global option is set
- architecture update is forced
-- architecture variant identified (using info, globals, and the last 
architecture)
-- existing architectures searched, if match return
-- if none match, a new architecture is created using the specified 
information

> That builds a new architecture based entirely on the defaults.  info.abfd is
> gone at that point, and that's how MIPS makes lots of its decisions.  OSABI
> support makes this even more pronounced.  I'd like to do:
> 	gdbarch_info_init_current (&info);
> but since architectures have an independent lifetime from BFD objects it's
> not clear how I can implement that.  Thoughts?

Yes, look at cris_gdbarch_init():

   else if (arches != NULL)
     {
       /* No bfd available.  Stick with the ABI from the most recently
          selected architecture of this same family (the head of arches
          always points to this).  (This is to avoid changing the ABI
          when the user updates the architecture with the 'set
          cris-version' command.)  */
       cris_abi = gdbarch_tdep (arches->gdbarch)->cris_abi;
     }
   else


Andrew