Re: RFA: Recording MIPS ABI selection in binaries

[cgd at sibyte dot com (Chris G. Demetriou)]

Nick Clifton <nickc@redhat.com> writes:
> : as far as i'm concerned, there could have been better use of the 
> : existing bits for ABIs (by enumeration, rather than flags)
> 
> Indeed, but as you say we are stuck with legacy code which we need to
> carry on supporting, so I doubt if these flags will change any time
> soon.

yes, i guess one of my questions was, how many of these flags are
defined by some pseudo-standard body, and how many were the invention
of the gnu tools folks.

and then, given that, how much trouble would be basically be to
declare some period of time in which nobody would set them, and
everybody would ignore them, or something, to lessen backward-compat
hassles.


Also, what's the specific case you're trying to solve?  (you said
you're talking about -mgp32... but what's the resulting ABI?  it looks
like existing bits can be used to expressed eabi32, eabi64, n32 o32,
and o64, but not "64" (but that seems to conflict with your original
statement that you need to differentiate between not using -mgp32 and
using it).



> : and is redundant with the aim of some existing mechanisms. 
> 
> Well it would be redundant if the current bits were reorganised, but I
> really doubt if that is going to happen.

certainly, nobody's going to solve the problem if every time it comes
up nobody resists new additions that go further from the 'right
thing.'  8-)


That actually makes me think:

the defined values for EF_MIPS_MACH are unused, and, really, per my
previous thought, EF_MIPS_MACH is really better expressed by something
like what you're currently proposing.  You could deprecate its use and
steal a few bits from it (looks like 4, non-contiguous), without
breaking backward compatibility with the defines in the existing
headers, if you are careful.


Also, if the goal is to have these replace the ABI flags, detection of
ABI conflicts using the new section indicators really should be added
to ld (or bfd).



cgd