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libstdc++: Simplify __detail::__distance_fw using 'if constexpr'

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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'.
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Jonathan Wakely 2024-11-01 12:38:29 +00:00 committed by Jonathan Wakely
parent 7750566163
commit b907cde027
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1 changed files with 10 additions and 14 deletions
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24
libstdc++-v3/include/bits/hashtable_policy.h
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@ -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
{