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<dt>Revision</dt> <dd><a href="http://trac.webkit.org/projects/webkit/changeset/244971">244971</a></dd>
<dt>Author</dt> <dd>cdumez@apple.com</dd>
<dt>Date</dt> <dd>2019-05-06 13:25:27 -0700 (Mon, 06 May 2019)</dd>
</dl>

<h3>Log Message</h3>
<pre>Add assertions to CachedFrame to help figure out crash in CachedFrame constructor
https://bugs.webkit.org/show_bug.cgi?id=197621

Reviewed by Geoffrey Garen.

Add release assertions to try and figure out who is sometimes detaching the document from its
frame while constructing CachedFrames for its descendants.

* dom/Document.cpp:
(WebCore::Document::detachFromFrame):
* dom/Document.h:
(WebCore::Document::setMayBeDetachedFromFrame):
* history/CachedFrame.cpp:
(WebCore::CachedFrame::CachedFrame):</pre>

<h3>Modified Paths</h3>
<ul>
<li><a href="#trunkSourceWebCoreChangeLog">trunk/Source/WebCore/ChangeLog</a></li>
<li><a href="#trunkSourceWebCoredomDocumentcpp">trunk/Source/WebCore/dom/Document.cpp</a></li>
<li><a href="#trunkSourceWebCoredomDocumenth">trunk/Source/WebCore/dom/Document.h</a></li>
<li><a href="#trunkSourceWebCorehistoryCachedFramecpp">trunk/Source/WebCore/history/CachedFrame.cpp</a></li>
</ul>

</div>
<div id="patch">
<h3>Diff</h3>
<a id="trunkSourceWebCoreChangeLog"></a>
<div class="modfile"><h4>Modified: trunk/Source/WebCore/ChangeLog (244970 => 244971)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/WebCore/ChangeLog   2019-05-06 20:24:29 UTC (rev 244970)
+++ trunk/Source/WebCore/ChangeLog      2019-05-06 20:25:27 UTC (rev 244971)
</span><span class="lines">@@ -1,3 +1,20 @@
</span><ins>+2019-05-06  Chris Dumez  <cdumez@apple.com>
+
+        Add assertions to CachedFrame to help figure out crash in CachedFrame constructor
+        https://bugs.webkit.org/show_bug.cgi?id=197621
+
+        Reviewed by Geoffrey Garen.
+
+        Add release assertions to try and figure out who is sometimes detaching the document from its
+        frame while constructing CachedFrames for its descendants.
+
+        * dom/Document.cpp:
+        (WebCore::Document::detachFromFrame):
+        * dom/Document.h:
+        (WebCore::Document::setMayBeDetachedFromFrame):
+        * history/CachedFrame.cpp:
+        (WebCore::CachedFrame::CachedFrame):
+
</ins><span class="cx"> 2019-05-06  Zan Dobersek  <zdobersek@igalia.com>
</span><span class="cx"> 
</span><span class="cx">         [GLib] WebCore::MainThreadSharedTimer should use the appropriate GSource priority, name
</span></span></pre></div>
<a id="trunkSourceWebCoredomDocumentcpp"></a>
<div class="modfile"><h4>Modified: trunk/Source/WebCore/dom/Document.cpp (244970 => 244971)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/WebCore/dom/Document.cpp    2019-05-06 20:24:29 UTC (rev 244970)
+++ trunk/Source/WebCore/dom/Document.cpp       2019-05-06 20:25:27 UTC (rev 244971)
</span><span class="lines">@@ -8130,6 +8130,10 @@
</span><span class="cx"> 
</span><span class="cx"> void Document::detachFromFrame()
</span><span class="cx"> {
</span><ins>+    // Assertion to help pinpint rdar://problem/49877867. If this hits, the crash trace should tell us
+    // which piece of code is detaching the document from its frame while constructing the CachedFrames.
+    RELEASE_ASSERT(m_mayBeDetachedFromFrame);
+
</ins><span class="cx">     observeFrame(nullptr);
</span><span class="cx"> }
</span><span class="cx"> 
</span></span></pre></div>
<a id="trunkSourceWebCoredomDocumenth"></a>
<div class="modfile"><h4>Modified: trunk/Source/WebCore/dom/Document.h (244970 => 244971)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/WebCore/dom/Document.h      2019-05-06 20:24:29 UTC (rev 244970)
+++ trunk/Source/WebCore/dom/Document.h 2019-05-06 20:25:27 UTC (rev 244971)
</span><span class="lines">@@ -1462,6 +1462,9 @@
</span><span class="cx">     TextAutoSizing& textAutoSizing();
</span><span class="cx"> #endif
</span><span class="cx"> 
</span><ins>+    // For debugging rdar://problem/49877867.
+    void setMayBeDetachedFromFrame(bool mayBeDetachedFromFrame) { m_mayBeDetachedFromFrame = mayBeDetachedFromFrame; }
+
</ins><span class="cx">     Logger& logger();
</span><span class="cx"> 
</span><span class="cx">     void hasStorageAccess(Ref<DeferredPromise>&& passedPromise);
</span><span class="lines">@@ -2059,6 +2062,7 @@
</span><span class="cx"> 
</span><span class="cx">     bool m_hasEvaluatedUserAgentScripts { false };
</span><span class="cx">     bool m_isRunningUserScripts { false };
</span><ins>+    bool m_mayBeDetachedFromFrame { true };
</ins><span class="cx"> #if ENABLE(APPLE_PAY)
</span><span class="cx">     bool m_hasStartedApplePaySession { false };
</span><span class="cx"> #endif
</span></span></pre></div>
<a id="trunkSourceWebCorehistoryCachedFramecpp"></a>
<div class="modfile"><h4>Modified: trunk/Source/WebCore/history/CachedFrame.cpp (244970 => 244971)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/WebCore/history/CachedFrame.cpp     2019-05-06 20:24:29 UTC (rev 244970)
+++ trunk/Source/WebCore/history/CachedFrame.cpp        2019-05-06 20:25:27 UTC (rev 244971)
</span><span class="lines">@@ -143,10 +143,20 @@
</span><span class="cx">     ASSERT(m_view);
</span><span class="cx">     ASSERT(m_document->pageCacheState() == Document::InPageCache);
</span><span class="cx"> 
</span><ins>+    RELEASE_ASSERT(m_document->domWindow());
+    RELEASE_ASSERT(m_document->frame());
+    RELEASE_ASSERT(m_document->domWindow()->frame());
+
+    // FIXME: We have evidence that constructing CachedFrames for descendant frames may detach the document from its frame (rdar://problem/49877867).
+    // This sets the flag to help find the guilty code.
+    m_document->setMayBeDetachedFromFrame(false);
+
</ins><span class="cx">     // Create the CachedFrames for all Frames in the FrameTree.
</span><span class="cx">     for (Frame* child = frame.tree().firstChild(); child; child = child->tree().nextSibling())
</span><span class="cx">         m_childFrames.append(std::make_unique<CachedFrame>(*child));
</span><span class="cx"> 
</span><ins>+    RELEASE_ASSERT(m_document->domWindow());
+    RELEASE_ASSERT(m_document->frame());
</ins><span class="cx">     RELEASE_ASSERT(m_document->domWindow()->frame());
</span><span class="cx"> 
</span><span class="cx">     // Active DOM objects must be suspended before we cache the frame script data.
</span><span class="lines">@@ -193,6 +203,7 @@
</span><span class="cx">     }
</span><span class="cx"> #endif
</span><span class="cx"> 
</span><ins>+    m_document->setMayBeDetachedFromFrame(true);
</ins><span class="cx">     m_document->detachFromCachedFrame(*this);
</span><span class="cx"> 
</span><span class="cx">     ASSERT_WITH_SECURITY_IMPLICATION(!m_documentLoader->isLoading());
</span></span></pre>
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