On Wed, Aug 27, 2025 at 12:48 PM Jonathan Wakely <jwak...@redhat.com> wrote:
> On Wed, 27 Aug 2025 at 11:36, Tomasz Kaminski <tkami...@redhat.com> wrote:
> >
> > Again, pretty printers needs to get updated:
> > iff --git a/libstdc++-v3/python/libstdcxx/v6/printers.py
> b/libstdc++-v3/python/libstdcxx/v6/printers.py
> > index 5f5963cb595..cf510433fd4 100644
> > --- a/libstdc++-v3/python/libstdcxx/v6/printers.py
> > +++ b/libstdc++-v3/python/libstdcxx/v6/printers.py
> > @@ -1749,7 +1749,7 @@ class StdCmpCatPrinter(printer_base):
> > if self._typename == 'strong_ordering' and self._val == 0:
> > name = 'equal'
> > else:
> > - names = {2: 'unordered', -1: 'less', 0: 'equivalent', 1:
> 'greater'}
> > + names = {-128: 'unordered', -1: 'less', 0: 'equivalent', 1:
> 'greater'}
>
> Can we keep 2 in the map as well, so that objects built with older
> versions of GCC can still be debugged with new printers.
>
That's a really good idea, modified it as suggested.
>
> i.e.
> # GCC 10-15 used 2 for unordered
> names = {-128: 'unordered', -1: 'less', 0: 'equivalent', 1: 'greater',
> 2: 'unordered'}
>
>
>
> > name = names[int(self._val)]
> > return 'std::{}::{}'.format(self._typename, name)
> >
> >
> > On Wed, Aug 27, 2025 at 12:05 PM 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
> >> * simplify defintion of _M_reverse
> >>
> >> Testing on x86_64-linux and powerpc64le-linux. OK for trunk when test
> >> passes?
> >>
> >> libstdc++-v3/libsupc++/compare | 22 +++++++++++++++-------
> >> 1 file changed, 15 insertions(+), 7 deletions(-)
> >>
> >> diff --git a/libstdc++-v3/libsupc++/compare
> b/libstdc++-v3/libsupc++/compare
> >> index 82b5c53139c..2624fa9144f 100644
> >> --- a/libstdc++-v3/libsupc++/compare
> >> +++ b/libstdc++-v3/libsupc++/compare
> >> @@ -56,7 +56,7 @@ namespace std _GLIBCXX_VISIBILITY(default)
> >>
> >> enum class _Ord : type { equivalent = 0, less = -1, greater = 1 };
> >>
> >> - enum class _Ncmp : type { _Unordered = 2 };
> >> + enum class _Ncmp : type { unordered = -__SCHAR_MAX__ - 1 };
> >>
> >> struct __unspec
> >> {
> >> @@ -66,7 +66,7 @@ namespace std _GLIBCXX_VISIBILITY(default)
> >>
> >> class partial_ordering
> >> {
> >> - // less=0xff, equiv=0x00, greater=0x01, unordered=0x02
> >> + // less=0xff, equiv=0x00, greater=0x01, unordered=0x80
> >> __cmp_cat::type _M_value;
> >>
> >> constexpr explicit
> >> @@ -82,6 +82,14 @@ namespace std _GLIBCXX_VISIBILITY(default)
> >> friend class weak_ordering;
> >> friend class strong_ordering;
> >>
> >> + [[__gnu__::__always_inline__]]
> >> + constexpr __cmp_cat::type
> >> + _M_reverse() const
> >> + {
> >> + // leaves _Ncmp::unordered unchanged
> >> + return static_cast<__cmp_cat::type>(-_M_value);
> >> + }
> >> +
> >> public:
> >> // valid values
> >> static const partial_ordering less;
> >> @@ -112,12 +120,12 @@ namespace std _GLIBCXX_VISIBILITY(default)
> >> [[nodiscard]]
> >> friend constexpr bool
> >> operator<=(partial_ordering __v, __cmp_cat::__unspec) noexcept
> >> - { return __v._M_value <= 0; }
> >> + { return __v._M_reverse() >= 0; }
> >>
> >> [[nodiscard]]
> >> friend constexpr bool
> >> operator>=(partial_ordering __v, __cmp_cat::__unspec) noexcept
> >> - { return __cmp_cat::type(__v._M_value & 1) == __v._M_value; }
> >> + { return __v._M_value >= 0; }
> >>
> >> [[nodiscard]]
> >> friend constexpr bool
> >> @@ -132,12 +140,12 @@ namespace std _GLIBCXX_VISIBILITY(default)
> >> [[nodiscard]]
> >> friend constexpr bool
> >> operator<=(__cmp_cat::__unspec, partial_ordering __v) noexcept
> >> - { return __cmp_cat::type(__v._M_value & 1) == __v._M_value; }
> >> + { return 0 <= __v._M_value; }
> >>
> >> [[nodiscard]]
> >> friend constexpr bool
> >> operator>=(__cmp_cat::__unspec, partial_ordering __v) noexcept
> >> - { return 0 >= __v._M_value; }
> >> + { return 0 <= __v._M_reverse(); }
> >>
> >> [[nodiscard]]
> >> friend constexpr partial_ordering
> >> @@ -166,7 +174,7 @@ namespace std _GLIBCXX_VISIBILITY(default)
> >> partial_ordering::greater(__cmp_cat::_Ord::greater);
> >>
> >> inline constexpr partial_ordering
> >> - partial_ordering::unordered(__cmp_cat::_Ncmp::_Unordered);
> >> + partial_ordering::unordered(__cmp_cat::_Ncmp::unordered);
> >>
> >> class weak_ordering
> >> {
> >> --
> >> 2.50.1
> >>
>
>
