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'.
---
Tested x86_64-linux. Pushed to trunk.
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 e5ad85ed9f1..ecf50313d09 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
{
--
2.47.0
