Just noticed this compile warning go by in my compile-spew: > nsSMILCompositor.cpp:56: warning: suggest parentheses around + or - inside shift That refers to this chunk: 50 /*static*/ PLDHashNumber 51 nsSMILCompositor::HashKey(KeyTypePointer aKey) 52 { 53 // Combine the 3 values into one numeric value, which will be hashed 54 return NS_PTR_TO_UINT32(aKey->mElement.get()) >> 4 + 55 NS_PTR_TO_INT32(aKey->mAttributeName.get()) + 56 (aKey->mIsCSS ? 1 : 0); 57 } 58 I think we need parens around the " XXX >> 4 " there. (rather than around the + as the warning suggests...) The fact that it suggests adding parens around the "+" makes me think the operator-precedence is currently such that we're using the latter 3/4 of that statement all as the amount to be shifted by... If so, that's broken -- but I guess at worst it just means our hash function isn't currently as good as it could be.

This chunk of code is from bug 534136, btw.

Just talked to sicking -- we should actually be right-shifting by 2, not 4. (If we don't shift at all, we'd always have 0's in the two lowest bits, since we're expecting those pointers to 4-byte-word-aligned. But we don't need to shift by more than 2.) Also: we should be using UINT32 (not INT32) on line 55, since that's what PLDHashNumber is typedef'd to.

Landed: http://hg.mozilla.org/mozilla-central/rev/8023fbbd3a70