Re: [Vm-dev] Suspect divideByZero protection in JPEGReaderPlugin

On Sun, Dec 23, 2012 at 01:12:03AM +0100, Nicolas Cellier wrote:

There is an incomplete division by zero protection in JPEGReaderPlugin:

nextSampleY ...snip... (sx = 0 and: [sy = 0]) ifFalse:[ dx := dx // sx. dy := dy // sy. ].

It only protect if both sx and sy are 0, but not in case (sx = 0 xor: sy = 0) Shouldn't it be:

    (sx = 0 or: [sy = 0]) ifFalse:[
            dx := dx // sx.
            dy := dy // sy.
    ].

Same in nextSampleCb nextSampleCr...

Nicolas

Good catch!

Patched for interpreter VM in VMMaker-dtl.261, and change set attached.

I wrote it this way for readability:

(sx ~= 0 and: [sy ~= 0]) ifTrue: [ dx := dx // sx. dy := dy // sy. ].

Dave