https://gcc.gnu.org/g:fcb3009a32dc33906934a2360e556dfeb98980cf
commit r16-3414-gfcb3009a32dc33906934a2360e556dfeb98980cf
Author: Tomasz Kamiński <tkami...@redhat.com>
Date: Tue Aug 26 14:34:35 2025 +0200
libsupc++: Change _Unordered comparison value to minimum value of signed
char.
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.
* python/libstdcxx/v6/printers.py: Add -128 as integer value
for unordered, keeping 2 to preserve backward compatibility.
Reviewed-by: Jonathan Wakely <jwak...@redhat.com>
Signed-off-by: Tomasz Kamiński <tkami...@redhat.com>
Diff:
---
libstdc++-v3/libsupc++/compare | 22 +++++++++++++++-------
libstdc++-v3/python/libstdcxx/v6/printers.py | 6 +++++-
2 files changed, 20 insertions(+), 8 deletions(-)
diff --git a/libstdc++-v3/libsupc++/compare b/libstdc++-v3/libsupc++/compare
index 82b5c53139c9..2624fa9144fb 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
{
diff --git a/libstdc++-v3/python/libstdcxx/v6/printers.py
b/libstdc++-v3/python/libstdcxx/v6/printers.py
index 5f5963cb5954..e5336b7fa89b 100644
--- a/libstdc++-v3/python/libstdcxx/v6/printers.py
+++ b/libstdc++-v3/python/libstdcxx/v6/printers.py
@@ -1749,7 +1749,11 @@ 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 = {
+ -1: 'less', 0: 'equivalent', 1: 'greater',
+ # GCC 10-15 used 2 for unordered
+ -128: 'unordered', 2: 'unordered'
+ }
name = names[int(self._val)]
return 'std::{}::{}'.format(self._typename, name)
