On Sun, 10 Nov 2024, Jonathan Wakely via Gcc wrote:
> But 1 - (10 * 0.1) won't, and so the warning is pointing out that any exact > equality comparisons can be affected by this kind of problem. If you don't > like the warning, don't enable it. I think OP's questions are in good faith and your last statement is unnecesarily passive-aggressive. If we respond to queries like that, it just reflects badly on us, because the implication is that we are not interested in criticisms for diagnostics or clarifying their behavior. Our warning is extremely simplistic, it warns even for 'x != x', and even the wording of the warning is bad: it says '... is unsafe' but there are no safety concerns here. I can see situations where warning for floating-point comparison makes sense even by default: float x; ... if (x != 0.1) // not 0.1f since 0.1f != 0.1 this could yield something like warning: comparison is always true but warning on every comparison is indefensible. > Does clang only have a special case for 0.0, or for any literal value? Their behavior is not documented, and it is not completely straightforward to me looking at the source, but they do not issue the warning if the value is exactly representable in the format (but they warn if it was implicitly cast from an integer, like in 'x == 0', which is probably a bug). They also suppress the warning in some other cases, e.g. for 'x == x'. Alexander
