[libcxx-commits] [libcxx] [libc++] Fix UB in <expected> related to "has value" flag (#68552) (PR #68733)

[Louis Dionne via libcxx-commits]

Jan =?utf-8?q?Kokemüller?= <jan.kokemueller at gmail.com>,
Jan =?utf-8?q?Kokemüller?= <jan.kokemueller at gmail.com>,
Jan =?utf-8?q?Kokemüller?= <jan.kokemueller at gmail.com>,
Jan =?utf-8?q?Kokemüller?= <jan.kokemueller at gmail.com>,
Jan =?utf-8?q?Kokemüller?= <jan.kokemueller at gmail.com>,
Jan =?utf-8?q?Kokemüller?= <jan.kokemueller at gmail.com>,
Jan =?utf-8?q?Kokemüller?= <jan.kokemueller at gmail.com>
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In-Reply-To: <llvm/llvm-project/pull/68733/libcxx at github.com>


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@@ -440,9 +399,10 @@ class expected {
       std::destroy_at(std::addressof(__union_.__val_));
     } else {
       std::destroy_at(std::addressof(__union_.__unex_));
-      __has_val_ = true;
     }
-    return *std::construct_at(std::addressof(__union_.__val_), std::forward<_Args>(__args)...);
+    std::construct_at(std::addressof(__union_.__val_), std::forward<_Args>(__args)...);
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ldionne wrote:

Can we add an updated test for `.emplace` as well?

https://github.com/llvm/llvm-project/pull/68733