https://gcc.gnu.org/g:b907cde027dc65af5842c06c50cfa12e2f58133b
commit r15-5037-gb907cde027dc65af5842c06c50cfa12e2f58133b Author: Jonathan Wakely <[email protected]> Date: Fri Nov 1 12:38:29 2024 +0000 libstdc++: Simplify __detail::__distance_fw using 'if constexpr' This uses 'if constexpr' instead of tag dispatching, removing the need for a second call using that tag, and simplifying the overload set that needs to be resolved for calls to __distance_fw. libstdc++-v3/ChangeLog: * include/bits/hashtable_policy.h (__distance_fw): Replace tag dispatching with 'if constexpr'. Diff: --- libstdc++-v3/include/bits/hashtable_policy.h | 24 ++++++++++-------------- 1 file changed, 10 insertions(+), 14 deletions(-) diff --git a/libstdc++-v3/include/bits/hashtable_policy.h b/libstdc++-v3/include/bits/hashtable_policy.h index e5ad85ed9f1a..ecf50313d09c 100644 --- a/libstdc++-v3/include/bits/hashtable_policy.h +++ b/libstdc++-v3/include/bits/hashtable_policy.h @@ -62,25 +62,21 @@ namespace __detail typename _Unused, typename _Traits> struct _Hashtable_base; +#pragma GCC diagnostic push +#pragma GCC diagnostic ignored "-Wc++17-extensions" // if constexpr // Helper function: return distance(first, last) for forward // iterators, or 0/1 for input iterators. - template<typename _Iterator> - inline typename std::iterator_traits<_Iterator>::difference_type - __distance_fw(_Iterator __first, _Iterator __last, - std::input_iterator_tag) - { return __first != __last ? 1 : 0; } - - template<typename _Iterator> - inline typename std::iterator_traits<_Iterator>::difference_type - __distance_fw(_Iterator __first, _Iterator __last, - std::forward_iterator_tag) - { return std::distance(__first, __last); } - template<typename _Iterator> inline typename std::iterator_traits<_Iterator>::difference_type __distance_fw(_Iterator __first, _Iterator __last) - { return __distance_fw(__first, __last, - std::__iterator_category(__first)); } + { + using _Cat = typename std::iterator_traits<_Iterator>::iterator_category; + if constexpr (is_convertible<_Cat, forward_iterator_tag>::value) + return std::distance(__first, __last); + else + return __first != __last ? 1 : 0; + } +#pragma GCC diagnostic pop struct _Identity {
