https://gcc.gnu.org/g:8543dc52d84662e3fc0b8b6ac5e98ce13ebe9ad9
commit r15-7632-g8543dc52d84662e3fc0b8b6ac5e98ce13ebe9ad9
Author: Patrick Palka <ppa...@redhat.com>
Date: Wed Feb 19 22:59:49 2025 -0500
libstdc++: Sync concat_view with final P2542 revision [PR115209]
Our concat_view implementation is accidentally based off of an older
revision of the paper, P2542R7 instead of R8. As far as I can tell the
only semantic change in the final revision is the relaxed constraints on
the iterator's iter/sent operator- overloads, which this patch updates.
This patch also simplifies the concat_view::end wording via C++26 pack
indexing as per the final revision. In turn we make the availability of
this library feature conditional on __cpp_pack_indexing. (Note pack
indexing is implemented in GCC 15 and Clang 19).
PR libstdc++/115209
libstdc++-v3/ChangeLog:
* include/bits/version.def (ranges_concat): Depend on
__cpp_pack_indexing.
* include/bits/version.h: Regenerate.
* include/std/ranges (__detail::__last_is_common): Remove.
(__detail::__all_but_first_sized): New.
(concat_view::end): Use C++26 pack indexing instead of
__last_is_common as per R8 of P2542.
(concat_view::iterator::operator-): Update constraints on
iter/sent overloads as per R8 of P2542.
Reviewed-by: Jonathan Wakely <jwak...@redhat.com>
Diff:
---
libstdc++-v3/include/bits/version.def | 1 +
libstdc++-v3/include/bits/version.h | 2 +-
libstdc++-v3/include/std/ranges | 38 +++++++++++++++--------------------
3 files changed, 18 insertions(+), 23 deletions(-)
diff --git a/libstdc++-v3/include/bits/version.def
b/libstdc++-v3/include/bits/version.def
index 002e560dc0d2..e75befe7f4b1 100644
--- a/libstdc++-v3/include/bits/version.def
+++ b/libstdc++-v3/include/bits/version.def
@@ -1842,6 +1842,7 @@ ftms = {
values = {
v = 202403;
cxxmin = 26;
+ extra_cond = "__cpp_pack_indexing";
};
};
diff --git a/libstdc++-v3/include/bits/version.h
b/libstdc++-v3/include/bits/version.h
index 70de189b1e0b..cd713ee54ea3 100644
--- a/libstdc++-v3/include/bits/version.h
+++ b/libstdc++-v3/include/bits/version.h
@@ -2036,7 +2036,7 @@
#undef __glibcxx_want_is_virtual_base_of
#if !defined(__cpp_lib_ranges_concat)
-# if (__cplusplus > 202302L)
+# if (__cplusplus > 202302L) && (__cpp_pack_indexing)
# define __glibcxx_ranges_concat 202403L
# if defined(__glibcxx_want_all) || defined(__glibcxx_want_ranges_concat)
# define __cpp_lib_ranges_concat 202403L
diff --git a/libstdc++-v3/include/std/ranges b/libstdc++-v3/include/std/ranges
index 5c795a90fbc2..22e0c9cae447 100644
--- a/libstdc++-v3/include/std/ranges
+++ b/libstdc++-v3/include/std/ranges
@@ -9683,12 +9683,8 @@ namespace ranges
&& __all_but_last_common<_Const, _Rs...>::value;
template<typename _Range, typename... _Rs>
- struct __last_is_common
- { static inline constexpr bool value = __last_is_common<_Rs...>::value;
};
-
- template<typename _Range>
- struct __last_is_common<_Range>
- { static inline constexpr bool value = common_range<_Range>; };
+ struct __all_but_first_sized
+ { static inline constexpr bool value = (sized_range<_Rs> && ...); };
} // namespace __detail
template<input_range... _Vs>
@@ -9726,13 +9722,11 @@ namespace ranges
constexpr auto
end() requires (!(__detail::__simple_view<_Vs> && ...))
{
+ constexpr auto __n = sizeof...(_Vs);
if constexpr ((semiregular<iterator_t<_Vs>> && ...)
- && __detail::__last_is_common<_Vs...>::value)
- {
- constexpr auto __n = sizeof...(_Vs);
- return iterator<false>(this, in_place_index<__n - 1>,
- ranges::end(std::get<__n - 1>(_M_views)));
- }
+ && common_range<_Vs...[__n - 1]>)
+ return iterator<false>(this, in_place_index<__n - 1>,
+ ranges::end(std::get<__n - 1>(_M_views)));
else
return default_sentinel;
}
@@ -9740,13 +9734,11 @@ namespace ranges
constexpr auto
end() const requires (range<const _Vs> && ...) &&
__detail::__concatable<const _Vs...>
{
+ constexpr auto __n = sizeof...(_Vs);
if constexpr ((semiregular<iterator_t<const _Vs>> && ...)
- && __detail::__last_is_common<const _Vs...>::value)
- {
- constexpr auto __n = sizeof...(_Vs);
- return iterator<true>(this, in_place_index<__n - 1>,
- ranges::end(std::get<__n - 1>(_M_views)));
- }
+ && common_range<const _Vs...[__n - 1]>)
+ return iterator<true>(this, in_place_index<__n - 1>,
+ ranges::end(std::get<__n - 1>(_M_views)));
else
return default_sentinel;
}
@@ -10128,8 +10120,9 @@ namespace ranges
friend constexpr difference_type
operator-(const iterator& __x, default_sentinel_t)
- requires __detail::__concat_is_random_access<_Const, _Vs...>
- && __detail::__last_is_common<__maybe_const_t<_Const, _Vs>...>::value
+ requires (sized_sentinel_for<sentinel_t<__maybe_const_t<_Const, _Vs>>,
+ iterator_t<__maybe_const_t<_Const, _Vs>>> &&
...)
+ && __detail::__all_but_first_sized<__maybe_const_t<_Const,
_Vs>...>::value
{
return _S_invoke_with_runtime_index([&]<size_t _Ix>() -> difference_type
{
auto __dx = ranges::distance(std::get<_Ix>(__x._M_it),
@@ -10148,8 +10141,9 @@ namespace ranges
friend constexpr difference_type
operator-(default_sentinel_t, const iterator& __x)
- requires __detail::__concat_is_random_access<_Const, _Vs...>
- && __detail::__last_is_common<__maybe_const_t<_Const, _Vs>...>::value
+ requires (sized_sentinel_for<sentinel_t<__maybe_const_t<_Const, _Vs>>,
+ iterator_t<__maybe_const_t<_Const, _Vs>>> &&
...)
+ && __detail::__all_but_first_sized<__maybe_const_t<_Const,
_Vs>...>::value
{ return -(__x - default_sentinel); }
friend constexpr decltype(auto)
