[OpenJDK 2D-Dev] New warnings in layout code

[Phil Race]

On 01/21/2016 01:50 PM, Omair Majid wrote:
> Hi,
>
> * Phil Race <philip.race at oracle.com> [2016-01-21 14:15]:
>> I don't think this is a problem in practice as we also have this test ..
>>> if (currGlyph < 0 || currGlyph >= glyphStorage.getGlyphCount()) {

> But the compiler won't optimize this one away completely, will it? Both
> parts of this check can be true or false. The checks that it is warning
> about will never be false (because, to the compiler, signed overflow
> doesn't exist).
I think my email wasn't clear in that the 'test' above is one that
is earlier, separate and valid and is sufficient to ensure that in
practice the *other* tests aren't needed.

i.e. when I wrote below :
>> Arguably the test could be removed but I would prefer to leave it in
^^^^^^^^^^^^^^^^^^^^^

I meant the other tests you pointed to. Not the one I cited.

>> and change the code it so it is actually tested.
>>
>> -fno-strict-overflow is just too compiler-specific and too far removed
>> from the code to be something I would want to rely upon long term.
> -fwrapv is another option and seems to be supported by gcc and clang, at
> least.
>
> That said, do you think some sort of add-and-check-for-overflow test
> would be suitable here? I can take a shot at implementing it, if you
> like.

Sure ! (to the code change option).
>> Interestingly I see the warning in the 8u71 logs using gcc 4.3.0,
>> but don't see the warning in RE's JDK 9 build log using gcc 4.9.2
>> I don't see it directly suppressed either but perhaps -Wno-type-limits masks
>> it ?
> On my box, I see the same warnings on jdk9. Please see the attached
> partial build log (from `make all LOG=trace`).

Right, I did not really doubt that the  underlying issue is there,
I just don't see a warning in our build logs and it could be due to the 
vagaries
of each compiler version.

-phil.

>
> Thanks,
> Omair
>