On Mon, Jan 28, 2013 at 08:47:14PM -0700, Orion Poplawski wrote:
> On 01/28/2013 07:54 PM, Alan W. Irwin wrote:
> > On 2013-01-28 17:01-0700 Orion Poplawski wrote:
> >
> >> Fedora rawhide has moved to gcc 3.8 and I'm seeing:
> >>
> >> $ ./x02a -dev psc -o x02a.psc
> >>
> >> raised CONSTRAINT_ERROR : x02a.adb:138 overflow check failed
> >>
> >> I'm taking that this is due to some increased checking with ada in
> >> 3.8. Thoughts?
> >
> > Hi Orion:
> >
> > I am virtually positive you meant the gcc-4.8 development effort which
> > (as far as I can tell) has not had a single release yet. So I am
> > changing the subject line accordingly. But please confirm that is
> > what you meant.
> >
> > If you meant gcc-4.8, there is always the chance that the symptom you
> > are seeing is a general problem caused by some recently introduced
> > version incompatibilty between gcc and Ada that still needs to be
> > worked out, i.e., a compiler inconsistency issue that has nothing to
> > do with PLplot development. On the other hand, it might be a PLplot
> > Ada issue that has been detected by (presumably) better error checking
> > for the latest versions of gcc/Ada as you have suggested. To help
> > decide between those two possibilities, could you give more details?
> >
> > For example, if you use the make -k option (to keep going despite
> > errors) are you able to compile all the Ada examples other than the
> > second one? If the issue is confined to just one of our examples, then
> > it is much more likely a PLplot Ada issue with that example (or the
> > API tested with that example) as you have suggested.
>
> Sorry, yes it is 4.8. Fedora is very tight with gcc development so we
> get things early - fun!
>
> The example compiles fine, it just doesn't run. Some others don't run
> either (see below).
>
> It looks very much like a floating point overflow condition is being
> triggered. With a debug statement it aborts at the start of the loop:
>
> i = 0 r1 = 3.00000000000000E-01
>
> I suspect that:
>
> 138 r(i+16) := Integer((r1 * 255.001) - 0.499999999999999);
>
> Has too many digits to be properly expressed. The comments indicate
> that it is dealing with some rounding/truncating differences. I suspect
> that gcc in 4.8 traps these conditions by default.
>
> Others:
>
> raised CONSTRAINT_ERROR : x02a.adb:141 overflow check failed
> raised CONSTRAINT_ERROR : x03a.adb:92 overflow check failed
> raised CONSTRAINT_ERROR : plplot_thin.adb:179 overflow check failed
> raised CONSTRAINT_ERROR : x12a.adb:105 overflow check failed
> raised CONSTRAINT_ERROR : x13a.adb:73 overflow check failed
> raised CONSTRAINT_ERROR : x14a.adb:218 overflow check failed
> raised CONSTRAINT_ERROR : plplot_thin.adb:179 overflow check failed
> raised CONSTRAINT_ERROR : x18a.adb:156 overflow check failed
> raised CONSTRAINT_ERROR : x19a.adb:192 overflow check failed
> raised CONSTRAINT_ERROR : plplot_thin.adb:241 overflow check failed
> raised CONSTRAINT_ERROR : plplot_auxiliary.adb:40 overflow check failed
> raised CONSTRAINT_ERROR : xthick02a.adb:136 overflow check failed
> raised CONSTRAINT_ERROR : xthick03a.adb:92 overflow check failed
> raised CONSTRAINT_ERROR : xthick12a.adb:104 overflow check failed
> raised CONSTRAINT_ERROR : xthick13a.adb:73 overflow check failed
> raised CONSTRAINT_ERROR : xthick14a.adb:218 overflow check failed
> raised CONSTRAINT_ERROR : xthick18a.adb:155 overflow check failed
> raised CONSTRAINT_ERROR : xthick19a.adb:192 overflow check failed
Urgh! Messing with float / integer values like this is just asking for
overflow / rounding problems.
What's wrong with using something like
r(i+16) := Integer(Float'Floor(r1 * 255.001));
(N.B. I've not tried this but I think it should work)
Andrew
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