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From: Jonathan Wakely <redi@gcc.gnu.org> To: gcc-cvs@gcc.gnu.org, libstdc++-cvs@gcc.gnu.org Subject: [gcc r12-4355] libstdc++: Improve diagnostics for misuses of output iterators Date: Tue, 12 Oct 2021 15:49:49 +0000 (GMT) [thread overview] Message-ID: <20211012154949.A72F5385741C@sourceware.org> (raw) https://gcc.gnu.org/g:d9dfd7ad3e0196f60a3fc6df6d65a40fb905409f commit r12-4355-gd9dfd7ad3e0196f60a3fc6df6d65a40fb905409f Author: Jonathan Wakely <jwakely@redhat.com> Date: Wed Sep 29 21:19:36 2021 +0100 libstdc++: Improve diagnostics for misuses of output iterators This adds deleted overloads so that the errors for invalid uses of std::advance and std::distance are easier to understand (see for example PR 102181). libstdc++-v3/ChangeLog: * include/bits/stl_iterator_base_funcs.h (__advance): Add deleted overload to improve diagnostics. (__distance): Likewise. Diff: --- libstdc++-v3/include/bits/stl_iterator_base_funcs.h | 14 ++++++++++++++ 1 file changed, 14 insertions(+) diff --git a/libstdc++-v3/include/bits/stl_iterator_base_funcs.h b/libstdc++-v3/include/bits/stl_iterator_base_funcs.h index e5afab7f4fd..fc6e9880de3 100644 --- a/libstdc++-v3/include/bits/stl_iterator_base_funcs.h +++ b/libstdc++-v3/include/bits/stl_iterator_base_funcs.h @@ -119,6 +119,13 @@ _GLIBCXX_END_NAMESPACE_CONTAINER input_iterator_tag); #endif +#if __cplusplus >= 201103L + // Give better error if std::distance called with a non-Cpp17InputIterator. + template<typename _OutputIterator> + void + __distance(_OutputIterator, _OutputIterator, output_iterator_tag) = delete; +#endif + /** * @brief A generalization of pointer arithmetic. * @param __first An input iterator. @@ -186,6 +193,13 @@ _GLIBCXX_END_NAMESPACE_CONTAINER __i += __n; } +#if __cplusplus >= 201103L + // Give better error if std::advance called with a non-Cpp17InputIterator. + template<typename _OutputIterator, typename _Distance> + void + __advance(_OutputIterator&, _Distance, output_iterator_tag) = delete; +#endif + /** * @brief A generalization of pointer arithmetic. * @param __i An input iterator.
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