[Bf-committers] PVS-Studio Static Analysis

[Jason Wilkins]

Oh, the way it is written now is confusing I think, since it does
several no-ops.

Wouldn't UINT_MAX be better?

On Tue, Apr 24, 2012 at 8:11 PM, Erwin Coumans <erwin.coumans at gmail.com> wrote:
> You are looking at the code that I fixed yesterday, see my commit message
> for details here:
> http://lists.blender.org/pipermail/bf-blender-cvs/2012-April/045090.html
>
>
>>>V610 Undefined behavior. Check the shift operator '<<. The left operand
> '(~0)' is negative. extern_bullet btquantizedbvh.h 82
>
> ~(0) is signed -1, negative, while ~(x&0) is positive unsigned, so it fixes
> the undefined behavior.
> Thanks,
> Erwin
>
>
>
> On 24 April 2012 18:01, Jason Wilkins <jason.a.wilkins at gmail.com> wrote:
>
>> This line in btQuantizedBvh.h confuses me:
>>
>> int     getTriangleIndex() const
>>        {
>>                btAssert(isLeafNode());
>>                unsigned int x=0;
>>                unsigned int y = (~(x&0))<<(31-MAX_NUM_PARTS_IN_BITS);
>>                // Get only the lower bits where the triangle index is
>> stored
>>                return (m_escapeIndexOrTriangleIndex&~(y));
>>        }
>>
>> Ostensibly the error is that ~0 is -1 (unsigned) and shifting an
>> unsigned is undefined or unspecified (forget which).
>>
>> But I'm actually confused why this code is written this way.
>> x=0, then x&0 == 0, even if x wasn't 0.
>>
>> Only after that do we get to the undefined behavior.
>>
>> I guess I could puzzle through it, but somebody else might just know :-)
>>
>> On Tue, Apr 24, 2012 at 7:30 PM, Jason Wilkins
>> <jason.a.wilkins at gmail.com> wrote:
>> > I'm working through them and fixing what Clang did not catch.
>> >
>> > I was going to say the same thing as Nicholas, code analysis is such a
>> > wide open field with virtually infinite number of things you can check
>> > for, that having more than one tool is a good idea.
>> >
>> > On Tue, Apr 24, 2012 at 6:30 PM, Nicholas Bishop
>> > <nicholasbishop at gmail.com> wrote:
>> >> Not necessarily; different static analyzers can detect different types
>> >> of potential problems. The PVS analysis contains some interesting
>> >> things like the "Misprint in a homogeneous code block" section that I
>> >> don't think clang's analyzer does.
>> >>
>> >> On Tue, Apr 24, 2012 at 7:20 PM, Tom M <letterrip at gmail.com> wrote:
>> >>> We have a page with generated CLang static analysis,
>> >>>
>> >>> http://clang.blenderheads.org/trunk/
>> >>>
>> >>> It probably shows the same bugs as PVS-Studio does.
>> >>>
>> >>> LetterRip
>> >>>
>> >>> On Tue, Apr 24, 2012 at 4:15 PM, Nicholas Bishop
>> >>> <nicholasbishop at gmail.com> wrote:
>> >>>> I think some of these have been fixed already in recent commits from
>> Campbell.
>> >>>>
>> >>>> On Tue, Apr 24, 2012 at 7:11 PM, Jason Wilkins
>> >>>> <jason.a.wilkins at gmail.com> wrote:
>> >>>>> http://www.viva64.com/en/b/0145/#ID0EO3BK
>> >>>>>
>> >>>>> It appears that Andrey Karpov has done an analysis of Blender source
>> >>>>> code using his PVS-Studio tool.  He did this just yesterday, so I
>> >>>>> assume the problems he found are still in the source.  He offers free
>> >>>>> licenses to open source project members (3500 euro software
>> otherwise,
>> >>>>> wow).
>> >>>>>
>> >>>>> I was thinking of investigating the problems he found and seeing if I
>> >>>>> could fix them.
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