From 21e5ee580b553a0aa28bae8c7463a9c5a8e7a646 Mon Sep 17 00:00:00 2001 From: Jonathan Wakely Date: Wed, 29 Mar 2023 22:43:16 +0100 Subject: [PATCH] libstdc++: Apply small fix from LWG 3843 to std::expected LWG 3843 adds some type requirements to std::expected::value to ensure that it can correctly copy the error value if it needs to throw an exception. We don't need to do anything to enforce that, because it will already be ill-formed if the type can't be copied. The issue also makes a small drive-by fix to ensure that a const E& is copied from the non-const value()& overload, which this change implements. libstdc++-v3/ChangeLog: * include/std/expected (expected::value() &): Use const lvalue for unex member passed to bad_expected_access constructor, as per LWG 3843. (cherry picked from commit ce39714a1ce58f2f32e8a44a224061290670db0f) --- libstdc++-v3/include/std/expected | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/libstdc++-v3/include/std/expected b/libstdc++-v3/include/std/expected index 3b97b7b59d85..ed123fb9b594 100644 --- a/libstdc++-v3/include/std/expected +++ b/libstdc++-v3/include/std/expected @@ -714,7 +714,8 @@ namespace __expected { if (_M_has_value) [[likely]] return _M_val; - _GLIBCXX_THROW_OR_ABORT(bad_expected_access<_Er>(_M_unex)); + const auto& __unex = _M_unex; + _GLIBCXX_THROW_OR_ABORT(bad_expected_access<_Er>(__unex)); } constexpr const _Tp&& -- 2.47.3