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<div id="msg">
<dl class="meta">
<dt>Revision</dt> <dd><a href="http://trac.webkit.org/projects/webkit/changeset/214086">214086</a></dd>
<dt>Author</dt> <dd>dino@apple.com</dd>
<dt>Date</dt> <dd>2017-03-16 17:51:02 -0700 (Thu, 16 Mar 2017)</dd>
</dl>

<h3>Log Message</h3>
<pre>WebGL: Improve index validation when using uint index values
https://bugs.webkit.org/show_bug.cgi?id=169798

Reviewed by Simon Fraser.

Source/WebCore:

Make sure that we test index validation with the correct type.
Also stop using -1 in WebGLBuffer to indicate non-existant values.

Test: fast/canvas/webgl/draw-elements-out-of-bounds-uint-index.html

* html/canvas/WebGL2RenderingContext.cpp:
(WebCore::WebGL2RenderingContext::validateIndexArrayConservative): Use optional&lt;&gt; and
unsigned values.
* html/canvas/WebGLBuffer.cpp: Use unsigned for maxIndex (they can't be negative)
and optional&lt;&gt; to indicate unknown value.
(WebCore::WebGLBuffer::getCachedMaxIndex):
(WebCore::WebGLBuffer::setCachedMaxIndex):
* html/canvas/WebGLBuffer.h:
* html/canvas/WebGLRenderingContext.cpp:
(WebCore::WebGLRenderingContext::validateIndexArrayConservative): Use optional&lt;&gt; and
unsigned values.
* html/canvas/WebGLRenderingContextBase.cpp:
(WebCore::WebGLRenderingContextBase::validateVertexAttributes): No need to check if
an unsigned value is less than zero.

LayoutTests:

* fast/canvas/webgl/draw-elements-out-of-bounds-uint-index-expected.txt: Added.
* fast/canvas/webgl/draw-elements-out-of-bounds-uint-index.html: Added.</pre>

<h3>Modified Paths</h3>
<ul>
<li><a href="#trunkLayoutTestsChangeLog">trunk/LayoutTests/ChangeLog</a></li>
<li><a href="#trunkSourceWebCoreChangeLog">trunk/Source/WebCore/ChangeLog</a></li>
<li><a href="#trunkSourceWebCorehtmlcanvasWebGL2RenderingContextcpp">trunk/Source/WebCore/html/canvas/WebGL2RenderingContext.cpp</a></li>
<li><a href="#trunkSourceWebCorehtmlcanvasWebGLBuffercpp">trunk/Source/WebCore/html/canvas/WebGLBuffer.cpp</a></li>
<li><a href="#trunkSourceWebCorehtmlcanvasWebGLBufferh">trunk/Source/WebCore/html/canvas/WebGLBuffer.h</a></li>
<li><a href="#trunkSourceWebCorehtmlcanvasWebGLRenderingContextcpp">trunk/Source/WebCore/html/canvas/WebGLRenderingContext.cpp</a></li>
<li><a href="#trunkSourceWebCorehtmlcanvasWebGLRenderingContextBasecpp">trunk/Source/WebCore/html/canvas/WebGLRenderingContextBase.cpp</a></li>
</ul>

<h3>Added Paths</h3>
<ul>
<li><a href="#trunkLayoutTestsfastcanvaswebgldrawelementsoutofboundsuintindexexpectedtxt">trunk/LayoutTests/fast/canvas/webgl/draw-elements-out-of-bounds-uint-index-expected.txt</a></li>
<li><a href="#trunkLayoutTestsfastcanvaswebgldrawelementsoutofboundsuintindexhtml">trunk/LayoutTests/fast/canvas/webgl/draw-elements-out-of-bounds-uint-index.html</a></li>
</ul>

</div>
<div id="patch">
<h3>Diff</h3>
<a id="trunkLayoutTestsChangeLog"></a>
<div class="modfile"><h4>Modified: trunk/LayoutTests/ChangeLog (214085 => 214086)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/LayoutTests/ChangeLog        2017-03-17 00:51:01 UTC (rev 214085)
+++ trunk/LayoutTests/ChangeLog        2017-03-17 00:51:02 UTC (rev 214086)
</span><span class="lines">@@ -1,3 +1,13 @@
</span><ins>+2017-03-16  Dean Jackson  &lt;dino@apple.com&gt;
+
+        WebGL: Improve index validation when using uint index values
+        https://bugs.webkit.org/show_bug.cgi?id=169798
+
+        Reviewed by Simon Fraser.
+
+        * fast/canvas/webgl/draw-elements-out-of-bounds-uint-index-expected.txt: Added.
+        * fast/canvas/webgl/draw-elements-out-of-bounds-uint-index.html: Added.
+
</ins><span class="cx"> 2017-03-16  Youenn Fablet  &lt;youenn@apple.com&gt;
</span><span class="cx"> 
</span><span class="cx">         Wrap legacy WebRTC API in runtime flag
</span></span></pre></div>
<a id="trunkLayoutTestsfastcanvaswebgldrawelementsoutofboundsuintindexexpectedtxt"></a>
<div class="addfile"><h4>Added: trunk/LayoutTests/fast/canvas/webgl/draw-elements-out-of-bounds-uint-index-expected.txt (0 => 214086)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/LayoutTests/fast/canvas/webgl/draw-elements-out-of-bounds-uint-index-expected.txt                                (rev 0)
+++ trunk/LayoutTests/fast/canvas/webgl/draw-elements-out-of-bounds-uint-index-expected.txt        2017-03-17 00:51:02 UTC (rev 214086)
</span><span class="lines">@@ -0,0 +1,10 @@
</span><ins>+Test of drawElements with out-of-bounds parameters using OES_element_index_uint
+
+On success, you will see a series of &quot;PASS&quot; messages, followed by &quot;TEST COMPLETE&quot;.
+
+PASS context.drawElements(context.LINES, 1, context.UNSIGNED_INT, 0) generated expected GL error: INVALID_OPERATION.
+PASS context.drawElements(context.LINES, 1, context.UNSIGNED_INT, 0) generated expected GL error: INVALID_OPERATION.
+PASS successfullyParsed is true
+
+TEST COMPLETE
+
</ins><span class="cx">Property changes on: trunk/LayoutTests/fast/canvas/webgl/draw-elements-out-of-bounds-uint-index-expected.txt
</span><span class="cx">___________________________________________________________________
</span></span></pre></div>
<a id="svneolstyle"></a>
<div class="addfile"><h4>Added: svn:eol-style</h4></div>
<ins>+native
</ins><span class="cx">\ No newline at end of property
</span><a id="svnkeywords"></a>
<div class="addfile"><h4>Added: svn:keywords</h4></div>
<ins>+Date Revision
</ins><span class="cx">\ No newline at end of property
</span><a id="svnmimetype"></a>
<div class="addfile"><h4>Added: svn:mime-type</h4></div>
<ins>+text/plain
</ins><span class="cx">\ No newline at end of property
</span><a id="trunkLayoutTestsfastcanvaswebgldrawelementsoutofboundsuintindexhtml"></a>
<div class="addfile"><h4>Added: trunk/LayoutTests/fast/canvas/webgl/draw-elements-out-of-bounds-uint-index.html (0 => 214086)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/LayoutTests/fast/canvas/webgl/draw-elements-out-of-bounds-uint-index.html                                (rev 0)
+++ trunk/LayoutTests/fast/canvas/webgl/draw-elements-out-of-bounds-uint-index.html        2017-03-17 00:51:02 UTC (rev 214086)
</span><span class="lines">@@ -0,0 +1,51 @@
</span><ins>+&lt;html&gt;
+&lt;head&gt;
+&lt;script src=&quot;../../../resources/js-test.js&quot;&gt;&lt;/script&gt;
+&lt;script src=&quot;resources/webgl-test.js&quot;&gt;&lt;/script&gt;
+&lt;/head&gt;
+&lt;body&gt;
+&lt;div id=&quot;description&quot;&gt;&lt;/div&gt;
+&lt;div id=&quot;console&quot;&gt;&lt;/div&gt;
+
+&lt;script&gt;
+description(&quot;Test of drawElements with out-of-bounds parameters using OES_element_index_uint&quot;);
+
+if (window.internals)
+    window.internals.settings.setWebGLErrorsToConsoleEnabled(false);
+
+var context = create3DContext();
+var program = loadStandardProgram(context);
+
+context.useProgram(program);
+context.getExtension(&quot;OES_element_index_uint&quot;);
+
+var buffer = context.createBuffer();
+context.bindBuffer(context.ARRAY_BUFFER, buffer);
+
+var data = new Uint8Array(0x100);
+context.bufferData(context.ARRAY_BUFFER, data, context.STATIC_DRAW);
+
+buffer = context.createBuffer();
+context.bindBuffer(context.ELEMENT_ARRAY_BUFFER, buffer);
+
+data = new Uint32Array(new ArrayBuffer(0x10));
+data[0] = 0xffffffff;
+for (let i = 1; i &lt; data.length; i++){
+    data[i] = 1;
+}
+context.bufferData(context.ELEMENT_ARRAY_BUFFER, data, context.STATIC_DRAW);
+
+context.enableVertexAttribArray(0);
+context.enableVertexAttribArray(1);
+context.vertexAttribPointer(0, 1, context.UNSIGNED_BYTE, false, 0, 0);
+context.vertexAttribPointer(1, 1, context.UNSIGNED_BYTE, false, 0, 0);
+
+shouldGenerateGLError(context, context.INVALID_OPERATION, &quot;context.drawElements(context.LINES, 1, context.UNSIGNED_INT, 0)&quot;);
+
+data[0] = 0xfffffffd;
+context.bufferData(context.ELEMENT_ARRAY_BUFFER, data, context.STATIC_DRAW);
+
+shouldGenerateGLError(context, context.INVALID_OPERATION, &quot;context.drawElements(context.LINES, 1, context.UNSIGNED_INT, 0)&quot;);
+&lt;/script&gt;
+&lt;/body&gt;
+&lt;/html&gt;
</ins><span class="cx">Property changes on: trunk/LayoutTests/fast/canvas/webgl/draw-elements-out-of-bounds-uint-index.html
</span><span class="cx">___________________________________________________________________
</span></span></pre></div>
<a id="svneolstyle"></a>
<div class="addfile"><h4>Added: svn:eol-style</h4></div>
<ins>+native
</ins><span class="cx">\ No newline at end of property
</span><a id="svnkeywords"></a>
<div class="addfile"><h4>Added: svn:keywords</h4></div>
<ins>+Date Revision
</ins><span class="cx">\ No newline at end of property
</span><a id="svnmimetype"></a>
<div class="addfile"><h4>Added: svn:mime-type</h4></div>
<ins>+text/html
</ins><span class="cx">\ No newline at end of property
</span><a id="trunkSourceWebCoreChangeLog"></a>
<div class="modfile"><h4>Modified: trunk/Source/WebCore/ChangeLog (214085 => 214086)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/WebCore/ChangeLog        2017-03-17 00:51:01 UTC (rev 214085)
+++ trunk/Source/WebCore/ChangeLog        2017-03-17 00:51:02 UTC (rev 214086)
</span><span class="lines">@@ -1,3 +1,30 @@
</span><ins>+2017-03-16  Dean Jackson  &lt;dino@apple.com&gt;
+
+        WebGL: Improve index validation when using uint index values
+        https://bugs.webkit.org/show_bug.cgi?id=169798
+
+        Reviewed by Simon Fraser.
+
+        Make sure that we test index validation with the correct type.
+        Also stop using -1 in WebGLBuffer to indicate non-existant values.
+
+        Test: fast/canvas/webgl/draw-elements-out-of-bounds-uint-index.html
+
+        * html/canvas/WebGL2RenderingContext.cpp:
+        (WebCore::WebGL2RenderingContext::validateIndexArrayConservative): Use optional&lt;&gt; and
+        unsigned values.
+        * html/canvas/WebGLBuffer.cpp: Use unsigned for maxIndex (they can't be negative)
+        and optional&lt;&gt; to indicate unknown value.
+        (WebCore::WebGLBuffer::getCachedMaxIndex):
+        (WebCore::WebGLBuffer::setCachedMaxIndex):
+        * html/canvas/WebGLBuffer.h:
+        * html/canvas/WebGLRenderingContext.cpp:
+        (WebCore::WebGLRenderingContext::validateIndexArrayConservative): Use optional&lt;&gt; and
+        unsigned values.
+        * html/canvas/WebGLRenderingContextBase.cpp:
+        (WebCore::WebGLRenderingContextBase::validateVertexAttributes): No need to check if
+        an unsigned value is less than zero.
+
</ins><span class="cx"> 2017-03-16  Simon Fraser  &lt;simon.fraser@apple.com&gt;
</span><span class="cx"> 
</span><span class="cx">         Improve the system tracing points
</span></span></pre></div>
<a id="trunkSourceWebCorehtmlcanvasWebGL2RenderingContextcpp"></a>
<div class="modfile"><h4>Modified: trunk/Source/WebCore/html/canvas/WebGL2RenderingContext.cpp (214085 => 214086)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/WebCore/html/canvas/WebGL2RenderingContext.cpp        2017-03-17 00:51:01 UTC (rev 214085)
+++ trunk/Source/WebCore/html/canvas/WebGL2RenderingContext.cpp        2017-03-17 00:51:02 UTC (rev 214086)
</span><span class="lines">@@ -1748,14 +1748,14 @@
</span><span class="cx">     auto* buffer = elementArrayBuffer-&gt;elementArrayBuffer();
</span><span class="cx">     ASSERT(buffer);
</span><span class="cx">     
</span><del>-    int maxIndex = elementArrayBuffer-&gt;getCachedMaxIndex(type);
-    if (maxIndex &lt; 0) {
</del><ins>+    std::optional&lt;unsigned&gt; maxIndex = elementArrayBuffer-&gt;getCachedMaxIndex(type);
+    if (!maxIndex) {
</ins><span class="cx">         // Compute the maximum index in the entire buffer for the given type of index.
</span><span class="cx">         switch (type) {
</span><span class="cx">         case GraphicsContext3D::UNSIGNED_BYTE: {
</span><span class="cx">             const GC3Dubyte* p = static_cast&lt;const GC3Dubyte*&gt;(buffer-&gt;data());
</span><span class="cx">             for (GC3Dsizeiptr i = 0; i &lt; numElements; i++)
</span><del>-                maxIndex = std::max(maxIndex, static_cast&lt;int&gt;(p[i]));
</del><ins>+                maxIndex = maxIndex ? std::max(maxIndex.value(), static_cast&lt;unsigned&gt;(p[i])) : static_cast&lt;unsigned&gt;(p[i]);
</ins><span class="cx">             break;
</span><span class="cx">         }
</span><span class="cx">         case GraphicsContext3D::UNSIGNED_SHORT: {
</span><span class="lines">@@ -1762,7 +1762,7 @@
</span><span class="cx">             numElements /= sizeof(GC3Dushort);
</span><span class="cx">             const GC3Dushort* p = static_cast&lt;const GC3Dushort*&gt;(buffer-&gt;data());
</span><span class="cx">             for (GC3Dsizeiptr i = 0; i &lt; numElements; i++)
</span><del>-                maxIndex = std::max(maxIndex, static_cast&lt;int&gt;(p[i]));
</del><ins>+                maxIndex = maxIndex ? std::max(maxIndex.value(), static_cast&lt;unsigned&gt;(p[i])) : static_cast&lt;unsigned&gt;(p[i]);
</ins><span class="cx">             break;
</span><span class="cx">         }
</span><span class="cx">         case GraphicsContext3D::UNSIGNED_INT: {
</span><span class="lines">@@ -1769,23 +1769,25 @@
</span><span class="cx">             numElements /= sizeof(GC3Duint);
</span><span class="cx">             const GC3Duint* p = static_cast&lt;const GC3Duint*&gt;(buffer-&gt;data());
</span><span class="cx">             for (GC3Dsizeiptr i = 0; i &lt; numElements; i++)
</span><del>-                maxIndex = std::max(maxIndex, static_cast&lt;int&gt;(p[i]));
</del><ins>+                maxIndex = maxIndex ? std::max(maxIndex.value(), static_cast&lt;unsigned&gt;(p[i])) : static_cast&lt;unsigned&gt;(p[i]);
</ins><span class="cx">             break;
</span><span class="cx">         }
</span><span class="cx">         default:
</span><span class="cx">             return false;
</span><span class="cx">         }
</span><del>-        elementArrayBuffer-&gt;setCachedMaxIndex(type, maxIndex);
</del><ins>+        if (maxIndex)
+            elementArrayBuffer-&gt;setCachedMaxIndex(type, maxIndex.value());
</ins><span class="cx">     }
</span><span class="cx">     
</span><del>-    if (maxIndex &gt;= 0) {
-        // The number of required elements is one more than the maximum
-        // index that will be accessed.
-        numElementsRequired = maxIndex + 1;
-        return true;
-    }
-    
-    return false;
</del><ins>+    if (!maxIndex)
+        return false;
+
+    // The number of required elements is one more than the maximum
+    // index that will be accessed.
+    numElementsRequired = maxIndex.value() + 1;
+
+    // Check for overflow.
+    return numElementsRequired &gt; 0;
</ins><span class="cx"> }
</span><span class="cx"> 
</span><span class="cx"> bool WebGL2RenderingContext::validateBlendEquation(const char* functionName, GC3Denum mode)
</span></span></pre></div>
<a id="trunkSourceWebCorehtmlcanvasWebGLBuffercpp"></a>
<div class="modfile"><h4>Modified: trunk/Source/WebCore/html/canvas/WebGLBuffer.cpp (214085 => 214086)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/WebCore/html/canvas/WebGLBuffer.cpp        2017-03-17 00:51:01 UTC (rev 214085)
+++ trunk/Source/WebCore/html/canvas/WebGLBuffer.cpp        2017-03-17 00:51:02 UTC (rev 214086)
</span><span class="lines">@@ -228,16 +228,16 @@
</span><span class="cx">     return m_byteLength;
</span><span class="cx"> }
</span><span class="cx"> 
</span><del>-int WebGLBuffer::getCachedMaxIndex(GC3Denum type)
</del><ins>+std::optional&lt;unsigned&gt; WebGLBuffer::getCachedMaxIndex(GC3Denum type)
</ins><span class="cx"> {
</span><span class="cx">     for (auto&amp; cache : m_maxIndexCache) {
</span><span class="cx">         if (cache.type == type)
</span><span class="cx">             return cache.maxIndex;
</span><span class="cx">     }
</span><del>-    return -1;
</del><ins>+    return std::nullopt;
</ins><span class="cx"> }
</span><span class="cx"> 
</span><del>-void WebGLBuffer::setCachedMaxIndex(GC3Denum type, int value)
</del><ins>+void WebGLBuffer::setCachedMaxIndex(GC3Denum type, unsigned value)
</ins><span class="cx"> {
</span><span class="cx">     for (auto&amp; cache : m_maxIndexCache) {
</span><span class="cx">         if (cache.type == type) {
</span></span></pre></div>
<a id="trunkSourceWebCorehtmlcanvasWebGLBufferh"></a>
<div class="modfile"><h4>Modified: trunk/Source/WebCore/html/canvas/WebGLBuffer.h (214085 => 214086)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/WebCore/html/canvas/WebGLBuffer.h        2017-03-17 00:51:01 UTC (rev 214085)
+++ trunk/Source/WebCore/html/canvas/WebGLBuffer.h        2017-03-17 00:51:02 UTC (rev 214086)
</span><span class="lines">@@ -52,11 +52,10 @@
</span><span class="cx">     GC3Dsizeiptr byteLength() const;
</span><span class="cx">     const JSC::ArrayBuffer* elementArrayBuffer() const { return m_elementArrayBuffer.get(); }
</span><span class="cx"> 
</span><del>-    // Gets the cached max index for the given type. Returns -1 if
-    // none has been set.
-    int getCachedMaxIndex(GC3Denum type);
</del><ins>+    // Gets the cached max index for the given type if one has been set.
+    std::optional&lt;unsigned&gt; getCachedMaxIndex(GC3Denum type);
</ins><span class="cx">     // Sets the cached max index for the given type.
</span><del>-    void setCachedMaxIndex(GC3Denum type, int value);
</del><ins>+    void setCachedMaxIndex(GC3Denum type, unsigned value);
</ins><span class="cx"> 
</span><span class="cx">     GC3Denum getTarget() const { return m_target; }
</span><span class="cx">     void setTarget(GC3Denum, bool forWebGL2);
</span><span class="lines">@@ -83,11 +82,10 @@
</span><span class="cx">     // that size.
</span><span class="cx">     struct MaxIndexCacheEntry {
</span><span class="cx">         GC3Denum type;
</span><del>-        int maxIndex;
</del><ins>+        unsigned maxIndex;
</ins><span class="cx">     };
</span><span class="cx">     // OpenGL ES 2.0 only has two valid index types (UNSIGNED_BYTE
</span><del>-    // and UNSIGNED_SHORT), but might as well leave open the
-    // possibility of adding others.
</del><ins>+    // and UNSIGNED_SHORT) plus one extension (UNSIGNED_INT).
</ins><span class="cx">     MaxIndexCacheEntry m_maxIndexCache[4];
</span><span class="cx">     unsigned m_nextAvailableCacheEntry { 0 };
</span><span class="cx"> 
</span></span></pre></div>
<a id="trunkSourceWebCorehtmlcanvasWebGLRenderingContextcpp"></a>
<div class="modfile"><h4>Modified: trunk/Source/WebCore/html/canvas/WebGLRenderingContext.cpp (214085 => 214086)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/WebCore/html/canvas/WebGLRenderingContext.cpp        2017-03-17 00:51:01 UTC (rev 214085)
+++ trunk/Source/WebCore/html/canvas/WebGLRenderingContext.cpp        2017-03-17 00:51:02 UTC (rev 214086)
</span><span class="lines">@@ -754,14 +754,14 @@
</span><span class="cx">     const ArrayBuffer* buffer = elementArrayBuffer-&gt;elementArrayBuffer();
</span><span class="cx">     ASSERT(buffer);
</span><span class="cx">     
</span><del>-    int maxIndex = elementArrayBuffer-&gt;getCachedMaxIndex(type);
-    if (maxIndex &lt; 0) {
</del><ins>+    std::optional&lt;unsigned&gt; maxIndex = elementArrayBuffer-&gt;getCachedMaxIndex(type);
+    if (!maxIndex) {
</ins><span class="cx">         // Compute the maximum index in the entire buffer for the given type of index.
</span><span class="cx">         switch (type) {
</span><span class="cx">         case GraphicsContext3D::UNSIGNED_BYTE: {
</span><span class="cx">             const GC3Dubyte* p = static_cast&lt;const GC3Dubyte*&gt;(buffer-&gt;data());
</span><span class="cx">             for (GC3Dsizeiptr i = 0; i &lt; numElements; i++)
</span><del>-                maxIndex = std::max(maxIndex, static_cast&lt;int&gt;(p[i]));
</del><ins>+                maxIndex = maxIndex ? std::max(maxIndex.value(), static_cast&lt;unsigned&gt;(p[i])) : static_cast&lt;unsigned&gt;(p[i]);
</ins><span class="cx">             break;
</span><span class="cx">         }
</span><span class="cx">         case GraphicsContext3D::UNSIGNED_SHORT: {
</span><span class="lines">@@ -768,7 +768,7 @@
</span><span class="cx">             numElements /= sizeof(GC3Dushort);
</span><span class="cx">             const GC3Dushort* p = static_cast&lt;const GC3Dushort*&gt;(buffer-&gt;data());
</span><span class="cx">             for (GC3Dsizeiptr i = 0; i &lt; numElements; i++)
</span><del>-                maxIndex = std::max(maxIndex, static_cast&lt;int&gt;(p[i]));
</del><ins>+                maxIndex = maxIndex ? std::max(maxIndex.value(), static_cast&lt;unsigned&gt;(p[i])) : static_cast&lt;unsigned&gt;(p[i]);
</ins><span class="cx">             break;
</span><span class="cx">         }
</span><span class="cx">         case GraphicsContext3D::UNSIGNED_INT: {
</span><span class="lines">@@ -777,23 +777,25 @@
</span><span class="cx">             numElements /= sizeof(GC3Duint);
</span><span class="cx">             const GC3Duint* p = static_cast&lt;const GC3Duint*&gt;(buffer-&gt;data());
</span><span class="cx">             for (GC3Dsizeiptr i = 0; i &lt; numElements; i++)
</span><del>-                maxIndex = std::max(maxIndex, static_cast&lt;int&gt;(p[i]));
</del><ins>+                maxIndex = maxIndex ? std::max(maxIndex.value(), static_cast&lt;unsigned&gt;(p[i])) : static_cast&lt;unsigned&gt;(p[i]);
</ins><span class="cx">             break;
</span><span class="cx">         }
</span><span class="cx">         default:
</span><span class="cx">             return false;
</span><span class="cx">         }
</span><del>-        elementArrayBuffer-&gt;setCachedMaxIndex(type, maxIndex);
</del><ins>+        if (maxIndex)
+            elementArrayBuffer-&gt;setCachedMaxIndex(type, maxIndex.value());
</ins><span class="cx">     }
</span><span class="cx">     
</span><del>-    if (maxIndex &gt;= 0) {
-        // The number of required elements is one more than the maximum
-        // index that will be accessed.
-        numElementsRequired = maxIndex + 1;
-        return true;
-    }
-    
-    return false;
</del><ins>+    if (!maxIndex)
+        return false;
+
+    // The number of required elements is one more than the maximum
+    // index that will be accessed.
+    numElementsRequired = maxIndex.value() + 1;
+
+    // Check for overflow.
+    return numElementsRequired &gt; 0;
</ins><span class="cx"> }
</span><span class="cx"> 
</span><span class="cx"> bool WebGLRenderingContext::validateBlendEquation(const char* functionName, GC3Denum mode)
</span></span></pre></div>
<a id="trunkSourceWebCorehtmlcanvasWebGLRenderingContextBasecpp"></a>
<div class="modfile"><h4>Modified: trunk/Source/WebCore/html/canvas/WebGLRenderingContextBase.cpp (214085 => 214086)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/WebCore/html/canvas/WebGLRenderingContextBase.cpp        2017-03-17 00:51:01 UTC (rev 214085)
+++ trunk/Source/WebCore/html/canvas/WebGLRenderingContextBase.cpp        2017-03-17 00:51:02 UTC (rev 214086)
</span><span class="lines">@@ -1781,7 +1781,7 @@
</span><span class="cx">             return false;
</span><span class="cx">     }
</span><span class="cx"> 
</span><del>-    if (elementCount &lt;= 0)
</del><ins>+    if (!elementCount)
</ins><span class="cx">         return true;
</span><span class="cx"> 
</span><span class="cx">     // Look in each consumed vertex attrib (by the current program).
</span></span></pre>
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