On Wed, 27 Aug 2025 at 11:05, Tomasz Kamiński <tkami...@redhat.com> wrote: > > For any minimum value of a signed type, its negation (with wraparound) results > in the same value, behaving like zero. Representing the unordered result with > this minimum value, along with 0 for equal, 1 for greater, and -1 for less > in partial_ordering, allows its value to be reversed using unary negation. > > The operator<=(partial_order, 0) now checks if the reversed value is positive. > This works correctly because the unordered value remains unchanged and thus > negative. > > libstdc++-v3/ChangeLog: > > * libsupc++/compare (_Ncmp::_Unordered): Rename and change the value > to minimum value of signed char. > (_Ncomp::unordered): Renamed from _Unordered, the name is reserved > by partial_ordered::unordered. > (partial_ordering::_M_reverse()): Define. > (operator<=(partial_ordering, __cmp_cat::__unspec)) > (operator>=(__cmp_cat::__unspec, partial_ordering)): Implemented > in terms of negated _M_value. > (operator>=(partial_ordering, __cmp_cat::__unspec)) > (operator<=(__cmp_cat::__unspec, partial_ordering)): Directly > compare _M_value, as unordered value is negative. > (partial_ordering::unordered): Handle _Ncmp::unoredred rename. > --- > Changes in v3: > * rename and simplify defintion of _Ncmp::unordered
Ah yes, we don't need to use an _Ugly name name for unordered. > * simplify defintion of _M_reverse > > Testing on x86_64-linux and powerpc64le-linux. OK for trunk when test > passes? OK for trunk with the pretty printer change included.
