The operator() for function objects introduced in C++20 (e.g., std::identity,
std::compare_three_way, std::ranges::equal) is now defined as static.
Although static operator() is a C++23 feature, it is supported in C++20 by
both GCC and clang (since their support was added in clang-16).
This change is not user-observable, as all affected operators are template
functions. Taking the address of such an operator requires casting to a pointer
to member function with a specific signature. The exact signature is unspecified
per C++20 [member.functions] p2 (e.g. due to potential parameters with default
arguments).
libstdc++-v3/ChangeLog:
* include/bits/ranges_cmp.h (std::identity::operator()):
(ranges::equal_to:operator(), ranges::not_equal_to:operator())
(ranges::greater::operator(), ranges::greater_equal::operator())
(ranges::less::operator(), ranges::less_equal::operator()):
Declare as static.
* libsupc++/compare (std::compare_three_way::operator()):
Declare as static.
Reviewed-by: Patrick Palka <[email protected]>
---
v3 makes this patch first in the series, as it reduces number of
explicit template specializations that needs to be handled later.
libstdc++-v3/include/bits/ranges_cmp.h | 34 +++++++++++++++-----------
libstdc++-v3/libsupc++/compare | 7 ++++--
2 files changed, 25 insertions(+), 16 deletions(-)
diff --git a/libstdc++-v3/include/bits/ranges_cmp.h
b/libstdc++-v3/include/bits/ranges_cmp.h
index cd5f7b8b37a..a53cd564563 100644
--- a/libstdc++-v3/include/bits/ranges_cmp.h
+++ b/libstdc++-v3/include/bits/ranges_cmp.h
@@ -46,11 +46,14 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
/// [func.identity] The identity function.
struct identity
{
+#pragma GCC diagnostic push
+#pragma GCC diagnostic ignored "-Wc++23-extensions" // static operator()
template<typename _Tp>
[[nodiscard]]
- constexpr _Tp&&
- operator()(_Tp&& __t) const noexcept
+ static constexpr _Tp&&
+ operator()(_Tp&& __t) noexcept
{ return std::forward<_Tp>(__t); }
+#pragma GCC diagnostic pop
using is_transparent = __is_transparent;
};
@@ -79,13 +82,15 @@ namespace ranges
// _GLIBCXX_RESOLVE_LIB_DEFECTS
// 3530 BUILTIN-PTR-MEOW should not opt the type out of syntactic checks
+#pragma GCC diagnostic push
+#pragma GCC diagnostic ignored "-Wc++23-extensions" // static operator()
/// ranges::equal_to function object type.
struct equal_to
{
template<typename _Tp, typename _Up>
requires equality_comparable_with<_Tp, _Up>
- constexpr bool
- operator()(_Tp&& __t, _Up&& __u) const
+ static constexpr bool
+ operator()(_Tp&& __t, _Up&& __u)
noexcept(noexcept(std::declval<_Tp>() == std::declval<_Up>()))
{ return std::forward<_Tp>(__t) == std::forward<_Up>(__u); }
@@ -97,8 +102,8 @@ namespace ranges
{
template<typename _Tp, typename _Up>
requires equality_comparable_with<_Tp, _Up>
- constexpr bool
- operator()(_Tp&& __t, _Up&& __u) const
+ static constexpr bool
+ operator()(_Tp&& __t, _Up&& __u)
noexcept(noexcept(std::declval<_Tp>() == std::declval<_Up>()))
{ return !equal_to{}(std::forward<_Tp>(__t), std::forward<_Up>(__u)); }
@@ -110,8 +115,8 @@ namespace ranges
{
template<typename _Tp, typename _Up>
requires totally_ordered_with<_Tp, _Up>
- constexpr bool
- operator()(_Tp&& __t, _Up&& __u) const
+ static constexpr bool
+ operator()(_Tp&& __t, _Up&& __u)
noexcept(noexcept(std::declval<_Tp>() < std::declval<_Up>()))
{
if constexpr (__detail::__less_builtin_ptr_cmp<_Tp, _Up>)
@@ -137,8 +142,8 @@ namespace ranges
{
template<typename _Tp, typename _Up>
requires totally_ordered_with<_Tp, _Up>
- constexpr bool
- operator()(_Tp&& __t, _Up&& __u) const
+ static constexpr bool
+ operator()(_Tp&& __t, _Up&& __u)
noexcept(noexcept(std::declval<_Up>() < std::declval<_Tp>()))
{ return less{}(std::forward<_Up>(__u), std::forward<_Tp>(__t)); }
@@ -150,8 +155,8 @@ namespace ranges
{
template<typename _Tp, typename _Up>
requires totally_ordered_with<_Tp, _Up>
- constexpr bool
- operator()(_Tp&& __t, _Up&& __u) const
+ static constexpr bool
+ operator()(_Tp&& __t, _Up&& __u)
noexcept(noexcept(std::declval<_Tp>() < std::declval<_Up>()))
{ return !less{}(std::forward<_Tp>(__t), std::forward<_Up>(__u)); }
@@ -163,13 +168,14 @@ namespace ranges
{
template<typename _Tp, typename _Up>
requires totally_ordered_with<_Tp, _Up>
- constexpr bool
- operator()(_Tp&& __t, _Up&& __u) const
+ static constexpr bool
+ operator()(_Tp&& __t, _Up&& __u)
noexcept(noexcept(std::declval<_Up>() < std::declval<_Tp>()))
{ return !less{}(std::forward<_Up>(__u), std::forward<_Tp>(__t)); }
using is_transparent = __is_transparent;
};
+#pragma GCC diagnostic pop
} // namespace ranges
#endif // __glibcxx_ranges
diff --git a/libstdc++-v3/libsupc++/compare b/libstdc++-v3/libsupc++/compare
index 458b47c3fca..08f2b2ba47e 100644
--- a/libstdc++-v3/libsupc++/compare
+++ b/libstdc++-v3/libsupc++/compare
@@ -573,10 +573,12 @@ namespace std _GLIBCXX_VISIBILITY(default)
// [cmp.object], typename compare_three_way
struct compare_three_way
{
+#pragma GCC diagnostic push
+#pragma GCC diagnostic ignored "-Wc++23-extensions" // static operator()
template<typename _Tp, typename _Up>
requires three_way_comparable_with<_Tp, _Up>
- constexpr auto
- operator() [[nodiscard]] (_Tp&& __t, _Up&& __u) const
+ static constexpr auto
+ operator() [[nodiscard]] (_Tp&& __t, _Up&& __u)
noexcept(noexcept(std::declval<_Tp>() <=> std::declval<_Up>()))
{
if constexpr (__detail::__3way_builtin_ptr_cmp<_Tp, _Up>)
@@ -592,6 +594,7 @@ namespace std _GLIBCXX_VISIBILITY(default)
else
return static_cast<_Tp&&>(__t) <=> static_cast<_Up&&>(__u);
}
+#pragma GCC diagnostic pop
using is_transparent = void;
};
--
2.51.1
