[patch, fortran] PR 47359 - warnings for constant conversion

[Steve Kargl]

On Mon, Jun 01, 2015 at 08:01:53PM +0200, Thomas Koenig wrote:
> Am 01.06.2015 um 15:40 schrieb Steve Kargl:
> > On Mon, Jun 01, 2015 at 08:34:24AM +0200, Thomas Koenig wrote:
> >> What would be the peferred alternative?
> 
> > Is it possible to detect the _knd suffix?
> 
> Yes, this is possible.
> 
> > If so, no
> > warning is my preference as it is never incorrect to
> > specify more digits than required for conversion from
> > ASCII to an internal representation.  This, of course,
> > assumes that the compiler doesn't have a bug.
> 
> :-)
> 
> >> > 
> >> > Comments?
> >> > 
> > I'm not a big fan of a proliferation of options.  As long
> > as the warning isn't triggered under -Wall, I suppose
> > I can live with -Wconversion-extra.
> 
> OK, so we have a few options.
> 
> a) Warn for
> 
>   print *,3.1415926535897932 with -Wconversion
> 
>   and warn for
> 
>   print *,3.1415926535_4 only with -Wconversion-extra
> 
> b) Like a) but supply two options to switch off the respective
>     warnings.
> 
> c) Warn for
> 
>   print *,3.1415926535 with -Wconversion-extra
> 
>   and don't warn for
> 
>   print *,3.141592653589_4
> 

This would be my first choice.  If a user actually specifies
a suffix, I assume that the user has given some thought 
to the preceding digits.

> d) Like now: Warn with -Wconversion-extra for both
> 
>    print *,3.1415926535
> 
>    and
> 
>    print *,3.14159265358979_4

This would be my second choice.

> What are people's prefrences on this?  Should we maybe ask on c.l.f
> (where we will get more opinions, certainly also differing)?

If you ask on c.l.f, you'll get differing opinions and most likely
a history lesson on what compilers did 40 years ago and how
PL/1 hands the issue. :-)

Don't let my person opinion be the sole driver/impediment.  
I do have a few comments on the patch itself.  I'll send those
later.

-- 
Steve