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<dl class="meta">
<dt>Revision</dt> <dd><a href="http://trac.webkit.org/projects/webkit/changeset/178372">178372</a></dd>
<dt>Author</dt> <dd>cdumez@apple.com</dd>
<dt>Date</dt> <dd>2015-01-13 13:21:40 -0800 (Tue, 13 Jan 2015)</dd>
</dl>
<h3>Log Message</h3>
<pre>Make WTF::Optional work with msvc 2013
https://bugs.webkit.org/show_bug.cgi?id=140401
Reviewed by Anders Carlsson.
Update the WTF::Optional implementation to use std::aligned_memory and
placement new instead of an unrestricted union because msvc 2013 still
doesn't support unrestricted unions.
This change is a pre-requirement to fix Bug 140347 as this change uses
WTF::Optional with types that have non-trivial copy constructors.
This change is covered by the existing Optional WTF test.
* wtf/Optional.h:</pre>
<h3>Modified Paths</h3>
<ul>
<li><a href="#trunkSourceWTFChangeLog">trunk/Source/WTF/ChangeLog</a></li>
<li><a href="#trunkSourceWTFwtfOptionalh">trunk/Source/WTF/wtf/Optional.h</a></li>
</ul>
</div>
<div id="patch">
<h3>Diff</h3>
<a id="trunkSourceWTFChangeLog"></a>
<div class="modfile"><h4>Modified: trunk/Source/WTF/ChangeLog (178371 => 178372)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/WTF/ChangeLog 2015-01-13 20:31:00 UTC (rev 178371)
+++ trunk/Source/WTF/ChangeLog 2015-01-13 21:21:40 UTC (rev 178372)
</span><span class="lines">@@ -1,3 +1,21 @@
</span><ins>+2015-01-13 Chris Dumez <cdumez@apple.com>
+
+ Make WTF::Optional work with msvc 2013
+ https://bugs.webkit.org/show_bug.cgi?id=140401
+
+ Reviewed by Anders Carlsson.
+
+ Update the WTF::Optional implementation to use std::aligned_memory and
+ placement new instead of an unrestricted union because msvc 2013 still
+ doesn't support unrestricted unions.
+
+ This change is a pre-requirement to fix Bug 140347 as this change uses
+ WTF::Optional with types that have non-trivial copy constructors.
+
+ This change is covered by the existing Optional WTF test.
+
+ * wtf/Optional.h:
+
</ins><span class="cx"> 2015-01-11 Sam Weinig <sam@webkit.org>
</span><span class="cx">
</span><span class="cx"> Remove support for SharedWorkers
</span></span></pre></div>
<a id="trunkSourceWTFwtfOptionalh"></a>
<div class="modfile"><h4>Modified: trunk/Source/WTF/wtf/Optional.h (178371 => 178372)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/WTF/wtf/Optional.h 2015-01-13 20:31:00 UTC (rev 178371)
+++ trunk/Source/WTF/wtf/Optional.h 2015-01-13 21:21:40 UTC (rev 178372)
</span><span class="lines">@@ -54,95 +54,79 @@
</span><span class="cx">
</span><span class="cx"> Optional(const T& value)
</span><span class="cx"> : m_isEngaged(true)
</span><del>- , m_value(value)
</del><span class="cx"> {
</span><ins>+ new (NotNull, &m_value) T(value);
</ins><span class="cx"> }
</span><span class="cx">
</span><span class="cx"> Optional(const Optional& other)
</span><span class="cx"> : m_isEngaged(other.m_isEngaged)
</span><span class="cx"> {
</span><span class="cx"> if (m_isEngaged)
</span><del>- new (NotNull, std::addressof(m_value)) T(other.m_value);
</del><ins>+ new (NotNull, &m_value) T(*other.asPtr());
</ins><span class="cx"> }
</span><span class="cx">
</span><span class="cx"> Optional(Optional&& other)
</span><span class="cx"> : m_isEngaged(other.m_isEngaged)
</span><span class="cx"> {
</span><span class="cx"> if (m_isEngaged)
</span><del>- new (NotNull, std::addressof(m_value)) T(WTF::move(other.m_value));
</del><ins>+ new (NotNull, &m_value) T(WTF::move(*other.asPtr()));
</ins><span class="cx"> }
</span><span class="cx">
</span><span class="cx"> Optional(T&& value)
</span><span class="cx"> : m_isEngaged(true)
</span><del>- , m_value(WTF::move(value))
</del><span class="cx"> {
</span><ins>+ new (NotNull, &m_value) T(WTF::move(value));
</ins><span class="cx"> }
</span><span class="cx">
</span><span class="cx"> template<typename... Args>
</span><span class="cx"> Optional(InPlaceTag, Args&&... args)
</span><span class="cx"> : m_isEngaged(true)
</span><del>- , m_value(std::forward<Args>(args)...)
</del><span class="cx"> {
</span><ins>+ new (NotNull, &m_value) T(std::forward<Args>(args)...);
</ins><span class="cx"> }
</span><span class="cx">
</span><span class="cx"> ~Optional()
</span><span class="cx"> {
</span><del>- if (m_isEngaged)
- m_value.~T();
</del><ins>+ destroy();
</ins><span class="cx"> }
</span><span class="cx">
</span><span class="cx"> Optional& operator=(NulloptTag)
</span><span class="cx"> {
</span><del>- if (m_isEngaged) {
- m_value.~T();
- m_isEngaged = false;
- }
</del><ins>+ destroy();
</ins><span class="cx"> return *this;
</span><span class="cx"> }
</span><span class="cx">
</span><span class="cx"> Optional& operator=(const Optional& other)
</span><span class="cx"> {
</span><del>- if (m_isEngaged == other.m_isEngaged) {
- if (m_isEngaged)
- m_value = other.m_value;
</del><ins>+ if (this == &other)
</ins><span class="cx"> return *this;
</span><del>- }
</del><span class="cx">
</span><del>- if (m_isEngaged)
- m_value.~T();
- else
- new (NotNull, std::addressof(m_value)) T(other.m_value);
- m_isEngaged = other.m_isEngaged;
-
</del><ins>+ destroy();
+ if (other.m_isEngaged) {
+ new (NotNull, &m_value) T(*other.asPtr());
+ m_isEngaged = true;
+ }
</ins><span class="cx"> return *this;
</span><span class="cx"> }
</span><span class="cx">
</span><span class="cx"> Optional& operator=(Optional&& other)
</span><span class="cx"> {
</span><del>- if (m_isEngaged == other.m_isEngaged) {
- if (m_isEngaged)
- m_value = WTF::move(other.m_value);
</del><ins>+ if (this == &other)
</ins><span class="cx"> return *this;
</span><del>- }
</del><span class="cx">
</span><del>- if (m_isEngaged)
- m_value.~T();
- else
- new (NotNull, std::addressof(m_value)) T(WTF::move(other.m_value));
- m_isEngaged = other.m_isEngaged;
-
</del><ins>+ destroy();
+ if (other.m_isEngaged) {
+ new (NotNull, &m_value) T(WTF::move(*other.asPtr()));
+ m_isEngaged = true;
+ }
</ins><span class="cx"> return *this;
</span><span class="cx"> }
</span><span class="cx">
</span><span class="cx"> template<typename U>
</span><span class="cx"> Optional& operator=(U&& u)
</span><span class="cx"> {
</span><del>- if (m_isEngaged) {
- m_value = std::forward<U>(u);
- return *this;
- }
-
- new (NotNull, std::addressof(m_value)) T(std::forward<U>(u));
</del><ins>+ destroy();
+ new (NotNull, &m_value) T(std::forward<U>(u));
</ins><span class="cx"> m_isEngaged = true;
</span><span class="cx"> return *this;
</span><span class="cx"> }
</span><span class="lines">@@ -152,29 +136,37 @@
</span><span class="cx"> T& value()
</span><span class="cx"> {
</span><span class="cx"> ASSERT(m_isEngaged);
</span><del>- return m_value;
</del><ins>+ return *asPtr();
</ins><span class="cx"> }
</span><span class="cx">
</span><span class="cx"> const T& value() const
</span><span class="cx"> {
</span><span class="cx"> ASSERT(m_isEngaged);
</span><del>- return m_value;
</del><ins>+ return *asPtr();
</ins><span class="cx"> }
</span><span class="cx">
</span><span class="cx"> template<typename U>
</span><span class="cx"> T valueOr(U&& value) const
</span><span class="cx"> {
</span><span class="cx"> if (m_isEngaged)
</span><del>- return m_value;
</del><ins>+ return *asPtr();
</ins><span class="cx">
</span><span class="cx"> return std::forward<U>(value);
</span><span class="cx"> }
</span><span class="cx">
</span><span class="cx"> private:
</span><ins>+ const T* asPtr() const { return reinterpret_cast<const T*>(&m_value); }
+ T* asPtr() { return reinterpret_cast<T*>(&m_value); }
+ void destroy()
+ {
+ if (m_isEngaged) {
+ asPtr()->~T();
+ m_isEngaged = false;
+ }
+ }
+
</ins><span class="cx"> bool m_isEngaged;
</span><del>- union {
- T m_value;
- };
</del><ins>+ typename std::aligned_storage<sizeof(T), std::alignment_of<T>::value>::type m_value;
</ins><span class="cx"> };
</span><span class="cx">
</span><span class="cx"> } // namespace WTF
</span></span></pre>
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