diff mbox series

[committed] libstdc++: Apply small fix from LWG 3843 to std::expected

Message ID 20230329233914.1405196-1-jwakely@redhat.com
State Committed
Commit ce39714a1ce58f2f32e8a44a224061290670db0f
Headers
Series [committed] libstdc++: Apply small fix from LWG 3843 to std::expected |

Commit Message

Jonathan Wakely March 29, 2023, 11:39 p.m. UTC 
  Tested powerpc64le-linux. Pushed to trunk.

-- >8 --

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.
---
 libstdc++-v3/include/std/expected | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)
diff mbox series

Patch

diff --git a/libstdc++-v3/include/std/expected b/libstdc++-v3/include/std/expected
index cb5754e2a68..058188248bb 100644
--- a/libstdc++-v3/include/std/expected
+++ b/libstdc++-v3/include/std/expected
@@ -736,7 +736,8 @@  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&&