Re: [RFC v2][3/3] Target FP printing: Use floatformat_to_string in tdep code

["Maciej W. Rozycki" <macro at imgtec dot com>]

On Tue, 17 Oct 2017, Ulrich Weigand wrote:

> >  I have now quickly checked it with a single target only and unfortunately 
> > the layout still has changed, e.g. in gdb.base/callfuncs.exp it used to 
> > be:
> > 
> > [...]
> >  f0:  0xd2f1a9fc flt: -5.18969491e+11   dbl: -0.001
> >  f1:  0xbf50624d flt: -0.813999951
> >  f2:  0x00000000 flt: 0                 dbl: 0
> >  f3:  0x00000000 flt: 0
> >  f4:  0xffffffff flt: -nan              dbl: -nan
> >  f5:  0xffffffff flt: -nan
> >  f6:  0xffffffff flt: -nan              dbl: -nan
> >  f7:  0xffffffff flt: -nan
> > [...]
> > 
> > while now it is:
> > 
> > [...]
> >  f0:  0xd2f1a9fc flt: -5.18969491e+11   dbl: -0.001
> >  f1:  0xbf50624d flt: -0.813999951
> >  f2:  0x00000000 flt: 0                 dbl: 0
> >  f3:  0x00000000 flt: 0
> >  f4:  0xffffffff flt: -nan(0x7fffff) dbl: -nan(0xfffffffffffff)
> >  f5:  0xffffffff flt: -nan(0x7fffff)
> >  f6:  0xffffffff flt: -nan(0x7fffff) dbl: -nan(0xfffffffffffff)
> >  f7:  0xffffffff flt: -nan(0x7fffff)
> > [...]
> > 
> > so it looks to me that the NaN formatter gets the character count wrong.
> 
> I see.  I guess we shouldn't use the special output strings at all
> when using formatted printing, but rely on the underlying printer
> to handle all cases.  (This actually matches today's behavior of
> printf_command, which my patches inadvertently changed.)
> 
> Can you verify using this additional patch on top of the series?

 This indeed brings the original output back, although I think printing 
the NaN payload does have a value.

 Would it be a tough problem to have it printed according to the width 
requested in the format specifier?  We know it's always going to take less 
than the maximum required for a floating-point number of the same 
floating-point format.

 As an independent change I think it would best be made with a separate 
patch though.

  Maciej