On Thu, 28 Aug 2025, Jonathan Wakely wrote:
> On Thu, 28 Aug 2025 at 14:26, Tomasz Kamiński <[email protected]> wrote:
> >
> > This slightly improve the readability of error message, by suggesting
> > that 0 (literal) is expected as argument:
> > invalid conversion from 'int' to 'std::__cmp_cat::__zero_literal*'
> >
> > libstdc++-v3/ChangeLog:
> >
> > * libsupc++/compare (__cmp_cat::__zero_literal): Rename
> > from __unspec.
> > (__cmp_cat::__unspec): Rename to __zero_literal.
> > (operator==, operator<, operator>, operator<=, operator>=):
> > Replace __cmp_cat::__unspec to __cmp_cat::__zero_literal.
> > * testsuite/18_support/comparisons/categories/zero_neg.cc:
> > New test for type that is convertilbe to any pointer.
> > ---
> > The improvement from the name is slight, and very subjective, so would
> > be interested in other people opinion.
>
> I think __literal_zero reads a little better for me than __zero_literal.
+1
>
>
> > Would like to preserve test, as I wondered about the case, and double
> > user-defined conversion didn't come to my mind imediatelly. This also
> > reason that we want to specify parameter as some type constructible from
> > pointer/nullptr_t instead of nullptr_t direclty.
> >
> > Testing on x86_64-linux locally.
> > OK for trunk for test?
>
> Yes, the test is OK for trunk now.
>
> > OK for trunk for rename?
> >
> > libstdc++-v3/libsupc++/compare | 70 +++++++++----------
> > .../comparisons/categories/zero_neg.cc | 16 +++++
> > 2 files changed, 51 insertions(+), 35 deletions(-)
> >
> > diff --git a/libstdc++-v3/libsupc++/compare b/libstdc++-v3/libsupc++/compare
> > index ca7c9095c3c..e956275042b 100644
> > --- a/libstdc++-v3/libsupc++/compare
> > +++ b/libstdc++-v3/libsupc++/compare
> > @@ -73,9 +73,9 @@ namespace std _GLIBCXX_VISIBILITY(default)
> > __make(_Ord __o) noexcept
> > { return _Ordering(__o); }
> >
> > - struct __unspec
> > + struct __zero_literal
> > {
> > - consteval __unspec(__unspec*) noexcept { }
> > + consteval __zero_literal(__zero_literal*) noexcept { }
> > };
> > }
> >
> > @@ -112,7 +112,7 @@ namespace std _GLIBCXX_VISIBILITY(default)
> > // comparisons
> > [[nodiscard]]
> > friend constexpr bool
> > - operator==(partial_ordering __v, __cmp_cat::__unspec) noexcept
> > + operator==(partial_ordering __v, __cmp_cat::__zero_literal) noexcept
> > { return __v._M_value == 0; }
> >
> > [[nodiscard]]
> > @@ -121,52 +121,52 @@ namespace std _GLIBCXX_VISIBILITY(default)
> >
> > [[nodiscard]]
> > friend constexpr bool
> > - operator< (partial_ordering __v, __cmp_cat::__unspec) noexcept
> > + operator< (partial_ordering __v, __cmp_cat::__zero_literal) noexcept
> > { return __v._M_value == -1; }
> >
> > [[nodiscard]]
> > friend constexpr bool
> > - operator> (partial_ordering __v, __cmp_cat::__unspec) noexcept
> > + operator> (partial_ordering __v, __cmp_cat::__zero_literal) noexcept
> > { return __v._M_value == 1; }
> >
> > [[nodiscard]]
> > friend constexpr bool
> > - operator<=(partial_ordering __v, __cmp_cat::__unspec) noexcept
> > + operator<=(partial_ordering __v, __cmp_cat::__zero_literal) noexcept
> > { return __v._M_reverse() >= 0; }
> >
> > [[nodiscard]]
> > friend constexpr bool
> > - operator>=(partial_ordering __v, __cmp_cat::__unspec) noexcept
> > + operator>=(partial_ordering __v, __cmp_cat::__zero_literal) noexcept
> > { return __v._M_value >= 0; }
> >
> > [[nodiscard]]
> > friend constexpr bool
> > - operator< (__cmp_cat::__unspec, partial_ordering __v) noexcept
> > + operator< (__cmp_cat::__zero_literal, partial_ordering __v) noexcept
> > { return __v._M_value == 1; }
> >
> > [[nodiscard]]
> > friend constexpr bool
> > - operator> (__cmp_cat::__unspec, partial_ordering __v) noexcept
> > + operator> (__cmp_cat::__zero_literal, partial_ordering __v) noexcept
> > { return __v._M_value == -1; }
> >
> > [[nodiscard]]
> > friend constexpr bool
> > - operator<=(__cmp_cat::__unspec, partial_ordering __v) noexcept
> > + operator<=(__cmp_cat::__zero_literal, partial_ordering __v) noexcept
> > { return 0 <= __v._M_value; }
> >
> > [[nodiscard]]
> > friend constexpr bool
> > - operator>=(__cmp_cat::__unspec, partial_ordering __v) noexcept
> > + operator>=(__cmp_cat::__zero_literal, partial_ordering __v) noexcept
> > { return 0 <= __v._M_reverse(); }
> >
> > [[nodiscard]]
> > friend constexpr partial_ordering
> > - operator<=>(partial_ordering __v, __cmp_cat::__unspec) noexcept
> > + operator<=>(partial_ordering __v, __cmp_cat::__zero_literal) noexcept
> > { return __v; }
> >
> > [[nodiscard]]
> > friend constexpr partial_ordering
> > - operator<=>(__cmp_cat::__unspec, partial_ordering __v) noexcept
> > + operator<=>(__cmp_cat::__zero_literal, partial_ordering __v) noexcept
> > { return partial_ordering(__cmp_cat::_Ord(__v._M_reverse())); }
> > };
> >
> > @@ -209,7 +209,7 @@ namespace std _GLIBCXX_VISIBILITY(default)
> > // comparisons
> > [[nodiscard]]
> > friend constexpr bool
> > - operator==(weak_ordering __v, __cmp_cat::__unspec) noexcept
> > + operator==(weak_ordering __v, __cmp_cat::__zero_literal) noexcept
> > { return __v._M_value == 0; }
> >
> > [[nodiscard]]
> > @@ -218,52 +218,52 @@ namespace std _GLIBCXX_VISIBILITY(default)
> >
> > [[nodiscard]]
> > friend constexpr bool
> > - operator< (weak_ordering __v, __cmp_cat::__unspec) noexcept
> > + operator< (weak_ordering __v, __cmp_cat::__zero_literal) noexcept
> > { return __v._M_value < 0; }
> >
> > [[nodiscard]]
> > friend constexpr bool
> > - operator> (weak_ordering __v, __cmp_cat::__unspec) noexcept
> > + operator> (weak_ordering __v, __cmp_cat::__zero_literal) noexcept
> > { return __v._M_value > 0; }
> >
> > [[nodiscard]]
> > friend constexpr bool
> > - operator<=(weak_ordering __v, __cmp_cat::__unspec) noexcept
> > + operator<=(weak_ordering __v, __cmp_cat::__zero_literal) noexcept
> > { return __v._M_value <= 0; }
> >
> > [[nodiscard]]
> > friend constexpr bool
> > - operator>=(weak_ordering __v, __cmp_cat::__unspec) noexcept
> > + operator>=(weak_ordering __v, __cmp_cat::__zero_literal) noexcept
> > { return __v._M_value >= 0; }
> >
> > [[nodiscard]]
> > friend constexpr bool
> > - operator< (__cmp_cat::__unspec, weak_ordering __v) noexcept
> > + operator< (__cmp_cat::__zero_literal, weak_ordering __v) noexcept
> > { return 0 < __v._M_value; }
> >
> > [[nodiscard]]
> > friend constexpr bool
> > - operator> (__cmp_cat::__unspec, weak_ordering __v) noexcept
> > + operator> (__cmp_cat::__zero_literal, weak_ordering __v) noexcept
> > { return 0 > __v._M_value; }
> >
> > [[nodiscard]]
> > friend constexpr bool
> > - operator<=(__cmp_cat::__unspec, weak_ordering __v) noexcept
> > + operator<=(__cmp_cat::__zero_literal, weak_ordering __v) noexcept
> > { return 0 <= __v._M_value; }
> >
> > [[nodiscard]]
> > friend constexpr bool
> > - operator>=(__cmp_cat::__unspec, weak_ordering __v) noexcept
> > + operator>=(__cmp_cat::__zero_literal, weak_ordering __v) noexcept
> > { return 0 >= __v._M_value; }
> >
> > [[nodiscard]]
> > friend constexpr weak_ordering
> > - operator<=>(weak_ordering __v, __cmp_cat::__unspec) noexcept
> > + operator<=>(weak_ordering __v, __cmp_cat::__zero_literal) noexcept
> > { return __v; }
> >
> > [[nodiscard]]
> > friend constexpr weak_ordering
> > - operator<=>(__cmp_cat::__unspec, weak_ordering __v) noexcept
> > + operator<=>(__cmp_cat::__zero_literal, weak_ordering __v) noexcept
> > { return weak_ordering(__cmp_cat::_Ord(-__v._M_value)); }
> > };
> >
> > @@ -309,7 +309,7 @@ namespace std _GLIBCXX_VISIBILITY(default)
> > // comparisons
> > [[nodiscard]]
> > friend constexpr bool
> > - operator==(strong_ordering __v, __cmp_cat::__unspec) noexcept
> > + operator==(strong_ordering __v, __cmp_cat::__zero_literal) noexcept
> > { return __v._M_value == 0; }
> >
> > [[nodiscard]]
> > @@ -318,52 +318,52 @@ namespace std _GLIBCXX_VISIBILITY(default)
> >
> > [[nodiscard]]
> > friend constexpr bool
> > - operator< (strong_ordering __v, __cmp_cat::__unspec) noexcept
> > + operator< (strong_ordering __v, __cmp_cat::__zero_literal) noexcept
> > { return __v._M_value < 0; }
> >
> > [[nodiscard]]
> > friend constexpr bool
> > - operator> (strong_ordering __v, __cmp_cat::__unspec) noexcept
> > + operator> (strong_ordering __v, __cmp_cat::__zero_literal) noexcept
> > { return __v._M_value > 0; }
> >
> > [[nodiscard]]
> > friend constexpr bool
> > - operator<=(strong_ordering __v, __cmp_cat::__unspec) noexcept
> > + operator<=(strong_ordering __v, __cmp_cat::__zero_literal) noexcept
> > { return __v._M_value <= 0; }
> >
> > [[nodiscard]]
> > friend constexpr bool
> > - operator>=(strong_ordering __v, __cmp_cat::__unspec) noexcept
> > + operator>=(strong_ordering __v, __cmp_cat::__zero_literal) noexcept
> > { return __v._M_value >= 0; }
> >
> > [[nodiscard]]
> > friend constexpr bool
> > - operator< (__cmp_cat::__unspec, strong_ordering __v) noexcept
> > + operator< (__cmp_cat::__zero_literal, strong_ordering __v) noexcept
> > { return 0 < __v._M_value; }
> >
> > [[nodiscard]]
> > friend constexpr bool
> > - operator> (__cmp_cat::__unspec, strong_ordering __v) noexcept
> > + operator> (__cmp_cat::__zero_literal, strong_ordering __v) noexcept
> > { return 0 > __v._M_value; }
> >
> > [[nodiscard]]
> > friend constexpr bool
> > - operator<=(__cmp_cat::__unspec, strong_ordering __v) noexcept
> > + operator<=(__cmp_cat::__zero_literal, strong_ordering __v) noexcept
> > { return 0 <= __v._M_value; }
> >
> > [[nodiscard]]
> > friend constexpr bool
> > - operator>=(__cmp_cat::__unspec, strong_ordering __v) noexcept
> > + operator>=(__cmp_cat::__zero_literal, strong_ordering __v) noexcept
> > { return 0 >= __v._M_value; }
> >
> > [[nodiscard]]
> > friend constexpr strong_ordering
> > - operator<=>(strong_ordering __v, __cmp_cat::__unspec) noexcept
> > + operator<=>(strong_ordering __v, __cmp_cat::__zero_literal) noexcept
> > { return __v; }
> >
> > [[nodiscard]]
> > friend constexpr strong_ordering
> > - operator<=>(__cmp_cat::__unspec, strong_ordering __v) noexcept
> > + operator<=>(__cmp_cat::__zero_literal, strong_ordering __v) noexcept
> > { return strong_ordering(__cmp_cat::_Ord(-__v._M_value)); }
> > };
> >
> > diff --git
> > a/libstdc++-v3/testsuite/18_support/comparisons/categories/zero_neg.cc
> > b/libstdc++-v3/testsuite/18_support/comparisons/categories/zero_neg.cc
> > index 2e6b9c14ddb..ce0ca8efa6f 100644
> > --- a/libstdc++-v3/testsuite/18_support/comparisons/categories/zero_neg.cc
> > +++ b/libstdc++-v3/testsuite/18_support/comparisons/categories/zero_neg.cc
> > @@ -23,6 +23,16 @@
> > // C++20 [cmp.categories.pre]
> > // "an argument other than a literal 0 is undefined"
> >
> > +struct PtrConv
> > +{
> > + template<typename T>
> > + consteval operator T*()
> > + { return nullptr; }
> > +
> > + consteval operator std::nullptr_t()
> > + { return nullptr; }
> > +};
> > +
> > void
> > test01()
> > {
> > @@ -48,6 +58,12 @@ test01()
> > std::partial_ordering::equivalent == nullptr;
> > std::weak_ordering::equivalent == nullptr;
> > std::strong_ordering::equivalent == nullptr;
> > +
> > + constexpr PtrConv c;
> > + // requires two user-defined conversion
> > + std::partial_ordering::equivalent == c; // { dg-error "no match for
> > 'operator=='" }
> > + std::weak_ordering::equivalent == c; // { dg-error "no match for
> > 'operator=='" }
> > + std::strong_ordering::equivalent == c; // { dg-error "no match for
> > 'operator=='" }
> > }
> >
> > // { dg-prune-output "reinterpret_cast.* is not a constant expression" }
> > --
> > 2.50.1
> >
>
>
