https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110477
--- Comment #4 from Jonathan Wakely <redi at gcc dot gnu.org> --- (In reply to Peter Dimov from comment #1) > Looks like a duplicate of > https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108742 and is fixed by casting > the rhs to (float), Yes, with -fexcess-precision=standard removal of excess precision only occurs when assigning to an lvalue or with an explicit cast, not for the equality comparison. An even simpler version is: double f = 2.1; assert( f == 2.1 ); // fails The value f has no excess precision bits, but the literal 2.1 is evaluated as an 80-bit float. The comparison promotes f to the type of the rhs, but it's lost its excess precision, so we're effectively doing (double)2.1L == 2.1L and that's false. > but any ordinary programmer would be baffled. Yes, very much so. (In reply to Peter Dimov from comment #3) > That's true, but the normal expectation of anyone using > -fexcess-precision=standard would be for it to apply consistently everywhere > (that is, as if FLT_EVAL_METHOD is 0.) > > Of course given that FLT_EVAL_METHOD is in a header, so unaffected by -f > options, it's not clear what can be done here. I think the rationale is that without -fexcess-precision=standard we do not correctly respect FLT_EVAL_METHOD, so its value doesn't matter. With -fexcess-precision=standard we do respect it ... with confusing consequences. The solution is to kill i387 ;-) -m32 -mfpmath=sse gives more sensible results.
