The issue submission talks about ranges that have InputIterators
as their iterator type. Even without any such range types, the added
test more or less shows that it's draconian to require a ForwardIterator
in std::next, since it seems perfectly reasonable to be able to std::next()
an iterator of an istream.
Testing on Linux-PPC64, ok for trunk if the full suite passes?
2017-11-19 Ville Voutilainen <ville.voutilai...@gmail.com>
Implement LWG 2353
* include/bits/stl_iterator_base_funcs.h (next):
Use InputIterator instead of ForwardIterator.
* testsuite/24_iterators/operations/lwg2353.cc: New.
* testsuite/24_iterators/operations/next_neg.cc: Remove.
diff --git a/libstdc++-v3/include/bits/stl_iterator_base_funcs.h
b/libstdc++-v3/include/bits/stl_iterator_base_funcs.h
index 86a93d3..ad84b39 100644
--- a/libstdc++-v3/include/bits/stl_iterator_base_funcs.h
+++ b/libstdc++-v3/include/bits/stl_iterator_base_funcs.h
@@ -208,14 +208,13 @@ _GLIBCXX_END_NAMESPACE_CONTAINER
#if __cplusplus >= 201103L
- template<typename _ForwardIterator>
- inline _GLIBCXX17_CONSTEXPR _ForwardIterator
- next(_ForwardIterator __x, typename
- iterator_traits<_ForwardIterator>::difference_type __n = 1)
+ template<typename _InputIterator>
+ inline _GLIBCXX17_CONSTEXPR _InputIterator
+ next(_InputIterator __x, typename
+ iterator_traits<_InputIterator>::difference_type __n = 1)
{
// concept requirements
- __glibcxx_function_requires(_ForwardIteratorConcept<
- _ForwardIterator>)
+ __glibcxx_function_requires(_InputIteratorConcept<_InputIterator>)
std::advance(__x, __n);
return __x;
}
diff --git a/libstdc++-v3/testsuite/24_iterators/operations/lwg2353.cc
b/libstdc++-v3/testsuite/24_iterators/operations/lwg2353.cc
new file mode 100644
index 0000000..4ce4077
--- /dev/null
+++ b/libstdc++-v3/testsuite/24_iterators/operations/lwg2353.cc
@@ -0,0 +1,26 @@
+// { dg-options "-D_GLIBCXX_CONCEPT_CHECKS" }
+// { dg-do run { target c++11 } }
+
+#include <iterator>
+#include <utility>
+#include <sstream>
+#include <string>
+#include <testsuite_hooks.h>
+
+template<typename Distance, typename InputRange>
+auto
+drop(Distance n, InputRange& rng)
+{
+ return std::make_pair(std::next(std::istream_iterator<char>(rng), n),
+ std::istream_iterator<char>()
+ );
+}
+
+int main()
+{
+ std::stringstream x("let let there be rock");
+ x << std::noskipws;
+ auto y = drop(4, x);
+ std::string z(y.first, y.second);
+ VERIFY(z == "let there be rock");
+}
diff --git a/libstdc++-v3/testsuite/24_iterators/operations/next_neg.cc
b/libstdc++-v3/testsuite/24_iterators/operations/next_neg.cc
deleted file mode 100644
index f3c20a1..0000000
--- a/libstdc++-v3/testsuite/24_iterators/operations/next_neg.cc
+++ /dev/null
@@ -1,42 +0,0 @@
-// Copyright (C) 2015-2017 Free Software Foundation, Inc.
-//
-// This file is part of the GNU ISO C++ Library. This library is free
-// software; you can redistribute it and/or modify it under the
-// terms of the GNU General Public License as published by the
-// Free Software Foundation; either version 3, or (at your option)
-// any later version.
-
-// This library is distributed in the hope that it will be useful,
-// but WITHOUT ANY WARRANTY; without even the implied warranty of
-// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
-// GNU General Public License for more details.
-
-// You should have received a copy of the GNU General Public License along
-// with this library; see the file COPYING3. If not see
-// <http://www.gnu.org/licenses/>.
-
-// { dg-options "-D_GLIBCXX_CONCEPT_CHECKS" }
-// { dg-do compile { target c++11 } }
-
-#include <iterator>
-
-struct X {};
-
-namespace std
-{
- template<>
- struct iterator_traits<const X*> : iterator_traits<X*>
- {
- using iterator_category = input_iterator_tag;
- using reference = const X&;
- using pointer = const X*;
- };
-}
-
-void
-test01()
-{
- const X array[1] = { };
- std::next(array);
- // { dg-error "input_iterator" "" { target *-*-* } 220 }
-}
