From d9dfd7ad3e0196f60a3fc6df6d65a40fb905409f Mon Sep 17 00:00:00 2001
From: Jonathan Wakely <jwakely@redhat.com>
Date: Wed, 29 Sep 2021 21:19:36 +0100
Subject: [PATCH] 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.
---
.../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 e5afab7f4fd3..fc6e9880de3a 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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