From: Philip Pronin <philipp@fb.com>
Date: Tue, 25 Oct 2016 06:27:16 +0000 (-0700)
Subject: fix Expected<..., eUnion> move / copy ctor
X-Git-Tag: v2016.10.31.00~8
X-Git-Url: http://plrg.eecs.uci.edu/git/?a=commitdiff_plain;h=c1ead85dff393f6e5c356073375bc955e1714403;p=folly.git

fix Expected<..., eUnion> move / copy ctor

Summary:
Consider `Expected<..., eUnion>(Expected&&)` ctor, where
`ExpectedUnion` move ctor would be called first, which is noop leaving
`which_`  uninitialized; then `MoveConstructible` ctor is executed, calling
`assignValue()`, which performs action depending on uninitialized `which_`.

Reviewed By: yfeldblum

Differential Revision: D4073199

fbshipit-source-id: 623660e7047afcebf9f72d83f91f84ff6078090f
---

diff --git a/folly/Expected.h b/folly/Expected.h
index 3de0a6d9..b4e63ee9 100644
--- a/folly/Expected.h
+++ b/folly/Expected.h
@@ -249,12 +249,11 @@ struct ExpectedUnion {
   union {
     Value value_;
     Error error_;
-    char ch_;
+    char ch_{};
   };
-  Which which_;
+  Which which_ = Which::eEmpty;
 
-  explicit constexpr ExpectedUnion(EmptyTag) noexcept
-      : ch_{}, which_(Which::eEmpty) {}
+  explicit constexpr ExpectedUnion(EmptyTag) noexcept {}
   template <class... Vs>
   explicit constexpr ExpectedUnion(ValueTag, Vs&&... vs) noexcept(
       noexcept(Value(static_cast<Vs&&>(vs)...)))