We can nearly mark layout/style as FAIL_ON_WARNINGS, but there's one remaining warning (on gcc): nsAnimationManager.cpp:269:80: warning: comparison between signed and unsigned integer expressions https://tbpl.mozilla.org/php/getParsedLog.php?id=18681193&tree=Try#error0 Filing this bug on fixing that.

The build warning is for the comparison in this ABORT_IF_FALSE: > const AnimationPropertySegment *segment = prop.mSegments.Elements(); [...] > NS_ABORT_IF_FALSE(segment - prop.mSegments.Elements() < > prop.mSegments.Length(), > "ran off end"); So, we're comparing a uint32 to the difference between two pointers. ptrdiff_t is ready-made for this sort of thing. Let's just cast Length() to that.

Try run that includes this patch (w/ build jobs only, just to verify that it builds everywhere): https://tbpl.mozilla.org/?tree=Try&rev=69a0703b85dc

Actually, I like this version slightly better. This version casts the pointer-difference to a size_t (after ensuring it'll be nonnegative), rather than casting the length to a ptrdiff_t. I like this better because it shouldn't be possible for it to do an invalid cast (whereas the previous version could technically perform an invalid cast, if Length() was larger than INT_MAX and we were on a 32-bit platform.)

Comment on attachment 700866 [details] [diff] [review] fix v2: cast pointer-subtraction to a size_t, after ensuring it'll be nonnegative r=dbaron