[PATCH 4/4] Don't throw an error in 'info registers' for unavailable MIPS GP registers.

[John Baldwin]

On Friday, April 28, 2017 02:51:41 PM Pedro Alves wrote:
> On 04/27/2017 08:37 PM, Maciej W. Rozycki wrote:
> > On Thu, 27 Apr 2017, Pedro Alves wrote:
> > 
> >>> The use of angle brackets with the latter variant is consistent with other 
> >>> targets, so I might have just a slight preference for it, but I'll be 
> >>> happy to accept input from other people.
> >>
> >> FWIW, I'd find using anything but <unavailable> when that's what
> >> GDB means to be making the port be gratuitously different.
> >> "<unavailable>" always means the same thing in gdb -- gdb knows
> >> the value materially exists, but it can't get at it for some
> >> reason (e.g., ptrace does not expose it, a core dump is trimmed, value
> >> not collect in a trace frame, etc.).
> > 
> >  If you think keeping the word the same across ports is essential, then 
> > `<unavl>' would be my second choice, at some aesthetical cost.
> 
> I'm not sure that trying to come up with short
> variants of these special values manually is the best option.
> 
> Another output you could see here is "<not saved>".
> GDB prints that if GDB figures out the register is not saved
> in a frame (or if the DWARF indicates that, via DW_CFA_undefined).

Unfortunately, even "<not saved>" is too long for the 8 character field
for a 32-bit register value.  One perhaps simple option would be to always
use the same table layout for 32-bit vs 64-bit (4 columns x 11 rows).  It
would mean doubling the lines that 'info registers' shows on 32-bit MIPS,
but it would still fit in 24 lines and would probably simplify the
implementation.

However, as you note, the primary goal is removing the error(), and I can
live with any format that is readable.

-- 
John Baldwin