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From: Patrick Palka <ppalka@gcc.gnu.org> To: gcc-cvs@gcc.gnu.org, libstdc++-cvs@gcc.gnu.org Subject: [gcc r12-173] libstdc++: Fix up lambda in join_view::_Iterator::operator++ [PR100290] Date: Tue, 27 Apr 2021 18:08:19 +0000 (GMT) [thread overview] Message-ID: <20210427180819.A176B3894C35@sourceware.org> (raw) https://gcc.gnu.org/g:85ef4b8d4eb3313a48b79c7e752891f9646bb246 commit r12-173-g85ef4b8d4eb3313a48b79c7e752891f9646bb246 Author: Patrick Palka <ppalka@redhat.com> Date: Tue Apr 27 14:07:46 2021 -0400 libstdc++: Fix up lambda in join_view::_Iterator::operator++ [PR100290] Currently, the return type of this lambda is decltype(auto), so the lambda ends up returning a copy of _M_parent->_M_inner rather than a reference to it when _S_ref_glvalue is false. This means _M_inner and ranges::end(__inner_range) are respectively an iterator and sentinel for different ranges, so comparing them is undefined. libstdc++-v3/ChangeLog: PR libstdc++/100290 * include/std/ranges (join_view::_Iterator::operator++): Correct the return type of the lambda to avoid returning a copy of _M_parent->_M_inner. * testsuite/std/ranges/adaptors/join.cc (test10): New test. Diff: --- libstdc++-v3/include/std/ranges | 2 +- libstdc++-v3/testsuite/std/ranges/adaptors/join.cc | 11 +++++++++++ 2 files changed, 12 insertions(+), 1 deletion(-) diff --git a/libstdc++-v3/include/std/ranges b/libstdc++-v3/include/std/ranges index 74075a2d6d3..09115e9b45f 100644 --- a/libstdc++-v3/include/std/ranges +++ b/libstdc++-v3/include/std/ranges @@ -2389,7 +2389,7 @@ namespace views::__adaptor constexpr _Iterator& operator++() { - auto&& __inner_range = [this] () -> decltype(auto) { + auto&& __inner_range = [this] () -> auto&& { if constexpr (_S_ref_is_glvalue) return *_M_outer; else diff --git a/libstdc++-v3/testsuite/std/ranges/adaptors/join.cc b/libstdc++-v3/testsuite/std/ranges/adaptors/join.cc index fb06a7698af..e6c71d771de 100644 --- a/libstdc++-v3/testsuite/std/ranges/adaptors/join.cc +++ b/libstdc++-v3/testsuite/std/ranges/adaptors/join.cc @@ -160,6 +160,16 @@ test09() static_assert(!requires { 0 | join; }); } +void +test10() +{ + // PR libstdc++/100290 + auto v = views::single(0) + | views::transform([](const auto& s) { return views::single(s); }) + | views::join; + VERIFY( ranges::next(v.begin()) == v.end() ); +} + int main() { @@ -172,4 +182,5 @@ main() test07(); test08(); test09(); + test10(); }
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