The code in question is:

    if (sprtemp[frame].rotate == false)

> Surely you wouldn't expect -1 == 0 to evaluate to true.

I wouldn't, no - but that's exactly what's happening in the test case.

Likewise, I wouldn't expect -1 == 1 to evaluate to true, but here we are.

The strict semantics of the new bool type may very well be "correct", and the reversed-test logic used by the compiler is certainly understandable and defensible - but given the long-established practice with integer types - i.e "if(some_var) {...}" and "if(!some_var) {...}" - that non-zero is "true" and zero is "false", it's a shame that the new type is inconsistent with that.