Fix gdb 8.1 Solaris/SPARC compilation (PR build/22206)

[Pedro Alves]

On 09/28/2017 01:40 PM, Rainer Orth wrote:
> Hi Wei-min,
> 
>> As for the issues you raised on gdb ADI support for Solaris/SPARC in the
>> bug report,
>> it's never intended to add that support for Solaris. While that Solaris
>> provided a totally
>> different ADI API was a factor, for example, Linux made the information of
>> ADI block
>> size available in the ELF aux record, one needed to make a syscall on
>> Solaris to get that
>> piece of information, it's certainly doable.  It was never planned,
>> however, and most likely
>> will never be.
> 
> this is extremely unfortunate, Oracle adding ADI support for one OS, but
> not for its own ;-(
> 
> However, what's worse is the way in which ADI support was added: when
> you add code to a file shared between different OSes like
> sparc64-tdep.c, it's your responsibility to make sure that this code at
> least doesn't break other SPARC targets.  Given how much of the code
> there isn't actually shared (and not sharable, it seems), the approach
> you've take seems wrong to me: it should have been properly factored
> between shared (sparc64-tdep.c) and os-private
> (e.g. sparc64-linux-tdep.c) files to avoid such breakage in the first
> place.

To be fair, that is the sort of issue that should have been pointed out
in review.  When I pushed for moving the ADI support out of the nat 
files and into tdep files for cross debugging, I don't think I even
remembered Solaris was a thing...  Not that I have anything against
Solaris, to be clear.  It just didn't cross my mind.

To me, this indicates a few things:

 - It's great that the Solaris port is again seeing activity, and
   we should strive to make sure that SPARC changes consider it.

 - But also someone needs to continually keep an eye on Solaris
   lest it ends up forgotten and broken again.  We need an official
   Solaris port maintainer.  Any takers?  :-)

 - It'd be desirable to have a SPARC Solaris machine build slave
   in the GDB buildbot, so that we can offload part of the work to 
   bots.  I wonder whether Oracle can help with this?  Might be
   difficult with the whole Solaris situation...

Thanks,
Pedro Alves