Bug 716439 added 2 new build warnings in FrameLayerBuilder.cpp: { ../../../mozilla/layout/base/FrameLayerBuilder.cpp: In member function 'void mozilla::{anonymous}::ContainerState::ThebesLayerData::UpdateCommonClipCount(const mozilla::FrameLayerBuilder::Clip&)': ../../../mozilla/layout/base/FrameLayerBuilder.cpp:1154:56: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] ../../../mozilla/layout/base/FrameLayerBuilder.cpp: In member function 'void mozilla::FrameLayerBuilder::Clip::ApplyRoundedRectsTo(gfxContext*, PRInt32, PRUint32, PRUint32) const': ../../../mozilla/layout/base/FrameLayerBuilder.cpp:2651:24: warning: comparison of unsigned expression >= 0 is always true [-Wtype-limits] } Both of these are in assertions, indicating that we might not be checking what we think we're checking in those cases. (I'm building w/ GCC 4.6.3)

I checked the code, the first warning is not a problem, I think (but will double check), mCommonClipCount is negative when not initialised, but here is compared to the length of a list. I will see if the warning can be avoided somehow. The second assertion is superfluous, I think it is a left over from an earlier version of the code. I'll make a patch to remove it asap.

To confirm, the first warning is unavoidable because mCommonClipCount is -1 initially, but is safe because we are inside an 'if (mCommonClipCount >= 0)' block.

I assume this will be OK without a Try run?

Comment on attachment 623541 [details] [diff] [review] remove the second warning Following the possible-callers of this method up, I found: > 2399 FrameLayerBuilder::DrawThebesLayer(ThebesLayer* aLayer, [...] > 2404 { [...] > 2414 PRInt32 commonClipCount; [...] > 2537 currentClip.ApplyTo(aContext, presContext, commonClipCount); (where ApplyTo is a wrapper for ApplyRoundedRectsTo, sort of) So commonClipCount is a signed value that we're converting to unsigned, without ever checking that it's nonnegative, AFAICT. So we could still potentially end up with a (wrapped) negative value at the place your assertion touches. Assuming I'm reading this correctly -- rather than dropping the assertion entirely, could you bump it up a few stack-levels to just before that ApplyTo call? Also, this patch only addresses one of the two warnings -- could you address the other one noted in comment 0 ("comparison between signed and unsigned integer expressions") as well?

(In reply to Daniel Holbert [:dholbert] from comment #4) > Also, this patch only addresses one of the two warnings -- could you address > the other one noted in comment 0 ("comparison between signed and unsigned > integer expressions") as well? oh, sorry, I missed comment 2. Could swap "mCommonClipCount" for "PRUint32(mCommonClipCount)" in that assertion, then? (perhaps with a comment noting that we're in a mCommonClipCount>=0 clause, if you like)

*Could we swap

The conversion from signed to unsigned is at line 1285, and is checked at line 1280. This is because there are two mCommonClipCounts in two different classes, one signed, one unsigned. The latter is used in DrawThebesLayer, there was a mistake in the signedness of commonClipCount that is corrected in the new patch.

Comment on attachment 623596 [details] [diff] [review] patch Ah, makes sense. Side note: I noticed that the _unsigned_ version of mCommonClipCounts is initialized to -1, which seems odd: > 533 class ThebesLayerItemsEntry : public nsPtrHashKey<ThebesLayer> { > 534 public: > 535 ThebesLayerItemsEntry(const ThebesLayer *key) : > 536 nsPtrHashKey<ThebesLayer>(key), mContainerLayerFrame(nsnull), > 537 mHasExplicitLastPaintOffset(false), mCommonClipCount(-1) {} [...] > 554 PRUint32 mCommonClipCount; Perhaps that should be initialized to PR_UINT32_MAX instead of -1, to be clearer about its valid range? (of course, they compute to the same value) Either way, r=me

Initialising ThebesLayerEntry::mCommonClipCount to 0, otherwise unchanged. Carrying r=dholbert

(Cool -- I'll take your word for it that 0 is a saner initial value than -1 was. :) )