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.
> 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
>
