[libc++][ranges] Fix ranges::join_view segmented iterator trait
#158347
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The outer iterator needs to move to the next segment when calling __compose. Without this change, `find_segment_if` would never reach the end of the join_view which caused erroneous result when calling `ranges::find` on a join_view of bidirectional ranges. Other specializations using the segmented iterator trait were likely to be affected as well.
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@llvm/pr-subscribers-libcxx Author: None (lbonn) ChangesThe outer iterator needs to move to the next segment when calling __compose. Without this change, Other specializations using the segmented iterator trait were likely to be affected as well. Fixes #158279, #93180 cc @philnik777 Full diff: https://github.com/llvm/llvm-project/pull/158347.diff 2 Files Affected:
diff --git a/libcxx/include/__ranges/join_view.h b/libcxx/include/__ranges/join_view.h
index 327b349f476a7..6097754f403ec 100644
--- a/libcxx/include/__ranges/join_view.h
+++ b/libcxx/include/__ranges/join_view.h
@@ -410,8 +410,12 @@ struct __segmented_iterator_traits<_JoinViewIterator> {
static constexpr _LIBCPP_HIDE_FROM_ABI _JoinViewIterator
__compose(__segment_iterator __seg_iter, __local_iterator __local_iter) {
- return _JoinViewIterator(
- std::move(__seg_iter).__get_data(), std::move(__seg_iter).__get_iter(), std::move(__local_iter));
+ auto&& __outer = std::move(__seg_iter).__get_iter();
+ if (__local_iter == ranges::end(*__outer)) {
+ ++__outer;
+ return _JoinViewIterator(*std::move(__seg_iter).__get_data(), __outer);
+ }
+ return _JoinViewIterator(std::move(__seg_iter).__get_data(), __outer, std::move(__local_iter));
}
};
diff --git a/libcxx/test/std/ranges/range.adaptors/range.join/range.join.iterator/find.pass.cpp b/libcxx/test/std/ranges/range.adaptors/range.join/range.join.iterator/find.pass.cpp
new file mode 100644
index 0000000000000..f8bee2227d0b9
--- /dev/null
+++ b/libcxx/test/std/ranges/range.adaptors/range.join/range.join.iterator/find.pass.cpp
@@ -0,0 +1,37 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+
+#include <algorithm>
+#include <cassert>
+#include <ranges>
+#include <type_traits>
+
+#include "../types.h"
+
+constexpr bool test() {
+ // Test the segmented iterator implementation of join_view
+ // https://github.com/llvm/llvm-project/issues/158279
+ {
+ int buffer1[2][1] = {{1}, {2}};
+ auto joined = std::views::join(buffer1);
+ assert(std::ranges::find(joined, 1) == std::ranges::begin(joined));
+ assert(std::ranges::find(joined, 2) == std::ranges::next(std::ranges::begin(joined)));
+ assert(std::ranges::find(joined, 3) == std::ranges::end(joined));
+ }
+
+ return true;
+}
+
+int main(int, char**) {
+ test();
+ static_assert(test());
+
+ return 0;
+}
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The outer iterator needs to move to the next segment when calling __compose.
Without this change,
find_segment_ifwould never reach the end of the join_view which caused erroneous result when callingranges::findon a join_view of bidirectional ranges.Other specializations using the segmented iterator trait were likely to be affected as well.
Fixes #158279, #93180
cc @philnik777