From 1af937eb6246ad7f63ebff03590e9eede33aca81 Mon Sep 17 00:00:00 2001 From: Patrick Palka Date: Fri, 16 Jul 2021 09:44:42 -0400 Subject: [PATCH] libstdc++: invalid default init in _CachedPosition [PR101231] The primary template for _CachedPosition is a dummy implementation for non-forward ranges, the iterators for which generally can't be cached. Because this implementation doesn't actually cache anything, _M_has_value is defined to be false and so calls to _M_get (which are always guarded by _M_has_value) are unreachable. Still, to suppress a "control reaches end of non-void function" warning I made _M_get return {}, but after P2325 input iterators are no longer necessarily default constructible so this workaround now breaks valid programs. This patch fixes this by instead using __builtin_unreachable to squelch the warning. PR libstdc++/101231 libstdc++-v3/ChangeLog: * include/std/ranges (_CachedPosition::_M_get): For non-forward ranges, just call __builtin_unreachable. * testsuite/std/ranges/istream_view.cc (test05): New test. --- libstdc++-v3/include/std/ranges | 2 +- libstdc++-v3/testsuite/std/ranges/istream_view.cc | 12 ++++++++++++ 2 files changed, 13 insertions(+), 1 deletion(-) diff --git a/libstdc++-v3/include/std/ranges b/libstdc++-v3/include/std/ranges index df74ac9..d791e15 100644 --- a/libstdc++-v3/include/std/ranges +++ b/libstdc++-v3/include/std/ranges @@ -1232,7 +1232,7 @@ namespace views::__adaptor _M_get(const _Range&) const { __glibcxx_assert(false); - return {}; + __builtin_unreachable(); } constexpr void diff --git a/libstdc++-v3/testsuite/std/ranges/istream_view.cc b/libstdc++-v3/testsuite/std/ranges/istream_view.cc index 369790e..2f15f78 100644 --- a/libstdc++-v3/testsuite/std/ranges/istream_view.cc +++ b/libstdc++-v3/testsuite/std/ranges/istream_view.cc @@ -83,6 +83,17 @@ test04() static_assert(!std::forward_iterator); } +void +test05() +{ + // PR libstdc++/101231 + auto words = std::istringstream{"42"}; + auto is = ranges::istream_view(words); + auto r = is | views::filter([](auto) { return true; }); + for (auto x : r) + ; +} + int main() { @@ -90,4 +101,5 @@ main() test02(); test03(); test04(); + test05(); } -- 2.7.4