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<dt>Revision</dt> <dd><a href="http://trac.webkit.org/projects/webkit/changeset/180564">180564</a></dd>
<dt>Author</dt> <dd>fpizlo@apple.com</dd>
<dt>Date</dt> <dd>2015-02-24 09:08:06 -0800 (Tue, 24 Feb 2015)</dd>
</dl>
<h3>Log Message</h3>
<pre>Our bizarre behavior on Arguments::defineOwnProperty should be deliberate rather than a spaghetti incident
https://bugs.webkit.org/show_bug.cgi?id=141951
Reviewed by Benjamin Poulain.
This patch has no behavioral change, but it simplifies a bunch of wrong code. The code is
still wrong in exactly the same way, but at least it's obvious what's going on. The wrongness
is covered by this bug: https://bugs.webkit.org/show_bug.cgi?id=141952.
* runtime/Arguments.cpp:
(JSC::Arguments::copyBackingStore): We should only see the arguments token; assert otherwise. This works because if the GC sees the butterfly token it calls the JSObject::copyBackingStore method directly.
(JSC::Arguments::defineOwnProperty): Make our bizarre behavior deliberate rather than an accident of a decade of patches.
* tests/stress/arguments-bizarre-behavior.js: Added.
(foo):
* tests/stress/arguments-bizarre-behaviour-disable-enumerability.js: Added. My choice of spellings of the word "behavio[u]r" is almost as consistent as our implementation of arguments.
(foo):
* tests/stress/arguments-custom-properties-gc.js: Added. I added this test because at first I was unsure if we GCd arguments correctly.
(makeBaseArguments):
(makeArray):
(cons):</pre>
<h3>Modified Paths</h3>
<ul>
<li><a href="#trunkSourceJavaScriptCoreChangeLog">trunk/Source/JavaScriptCore/ChangeLog</a></li>
<li><a href="#trunkSourceJavaScriptCoreruntimeArgumentscpp">trunk/Source/JavaScriptCore/runtime/Arguments.cpp</a></li>
</ul>
<h3>Added Paths</h3>
<ul>
<li><a href="#trunkSourceJavaScriptCoretestsstressargumentsbizarrebehaviorjs">trunk/Source/JavaScriptCore/tests/stress/arguments-bizarre-behavior.js</a></li>
<li><a href="#trunkSourceJavaScriptCoretestsstressargumentsbizarrebehaviourdisableenumerabilityjs">trunk/Source/JavaScriptCore/tests/stress/arguments-bizarre-behaviour-disable-enumerability.js</a></li>
<li><a href="#trunkSourceJavaScriptCoretestsstressargumentscustompropertiesgcjs">trunk/Source/JavaScriptCore/tests/stress/arguments-custom-properties-gc.js</a></li>
</ul>
</div>
<div id="patch">
<h3>Diff</h3>
<a id="trunkSourceJavaScriptCoreChangeLog"></a>
<div class="modfile"><h4>Modified: trunk/Source/JavaScriptCore/ChangeLog (180563 => 180564)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/JavaScriptCore/ChangeLog 2015-02-24 17:07:46 UTC (rev 180563)
+++ trunk/Source/JavaScriptCore/ChangeLog 2015-02-24 17:08:06 UTC (rev 180564)
</span><span class="lines">@@ -1,3 +1,26 @@
</span><ins>+2015-02-23 Filip Pizlo <fpizlo@apple.com>
+
+ Our bizarre behavior on Arguments::defineOwnProperty should be deliberate rather than a spaghetti incident
+ https://bugs.webkit.org/show_bug.cgi?id=141951
+
+ Reviewed by Benjamin Poulain.
+
+ This patch has no behavioral change, but it simplifies a bunch of wrong code. The code is
+ still wrong in exactly the same way, but at least it's obvious what's going on. The wrongness
+ is covered by this bug: https://bugs.webkit.org/show_bug.cgi?id=141952.
+
+ * runtime/Arguments.cpp:
+ (JSC::Arguments::copyBackingStore): We should only see the arguments token; assert otherwise. This works because if the GC sees the butterfly token it calls the JSObject::copyBackingStore method directly.
+ (JSC::Arguments::defineOwnProperty): Make our bizarre behavior deliberate rather than an accident of a decade of patches.
+ * tests/stress/arguments-bizarre-behavior.js: Added.
+ (foo):
+ * tests/stress/arguments-bizarre-behaviour-disable-enumerability.js: Added. My choice of spellings of the word "behavio[u]r" is almost as consistent as our implementation of arguments.
+ (foo):
+ * tests/stress/arguments-custom-properties-gc.js: Added. I added this test because at first I was unsure if we GCd arguments correctly.
+ (makeBaseArguments):
+ (makeArray):
+ (cons):
+
</ins><span class="cx"> 2015-02-23 Commit Queue <commit-queue@webkit.org>
</span><span class="cx">
</span><span class="cx"> Unreviewed, rolling out r180547 and r180550.
</span></span></pre></div>
<a id="trunkSourceJavaScriptCoreruntimeArgumentscpp"></a>
<div class="modfile"><h4>Modified: trunk/Source/JavaScriptCore/runtime/Arguments.cpp (180563 => 180564)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/JavaScriptCore/runtime/Arguments.cpp 2015-02-24 17:07:46 UTC (rev 180563)
+++ trunk/Source/JavaScriptCore/runtime/Arguments.cpp 2015-02-24 17:08:06 UTC (rev 180564)
</span><span class="lines">@@ -81,7 +81,7 @@
</span><span class="cx"> }
</span><span class="cx">
</span><span class="cx"> default:
</span><del>- return;
</del><ins>+ RELEASE_ASSERT_NOT_REACHED();
</ins><span class="cx"> }
</span><span class="cx"> }
</span><span class="cx">
</span><span class="lines">@@ -295,35 +295,33 @@
</span><span class="cx"> unsigned i = propertyName.asIndex();
</span><span class="cx"> if (i < thisObject->m_numArguments) {
</span><span class="cx"> RELEASE_ASSERT(i < PropertyName::NotAnIndex);
</span><del>- // If the property is not yet present on the object, and is not yet marked as deleted, then add it now.
- PropertySlot slot(thisObject);
- if (!thisObject->isDeletedArgument(i) && !JSObject::getOwnPropertySlot(thisObject, exec, propertyName, slot)) {
- JSValue value = thisObject->tryGetArgument(i);
- ASSERT(value);
- object->putDirectMayBeIndex(exec, propertyName, value);
- }
- if (!Base::defineOwnProperty(object, exec, propertyName, descriptor, shouldThrow))
- return false;
-
- // From ES 5.1, 10.6 Arguments Object
- // 5. If the value of isMapped is not undefined, then
</del><ins>+
</ins><span class="cx"> if (thisObject->isArgument(i)) {
</span><del>- // a. If IsAccessorDescriptor(Desc) is true, then
- if (descriptor.isAccessorDescriptor()) {
- // i. Call the [[Delete]] internal method of map passing P, and false as the arguments.
- thisObject->tryDeleteArgument(exec->vm(), i);
- } else { // b. Else
- // i. If Desc.[[Value]] is present, then
- // 1. Call the [[Put]] internal method of map passing P, Desc.[[Value]], and Throw as the arguments.
</del><ins>+ if (!descriptor.isAccessorDescriptor()) {
+ // If the property is not deleted and we are using a non-accessor descriptor, then
+ // make sure that the aliased argument sees the value.
</ins><span class="cx"> if (descriptor.value())
</span><span class="cx"> thisObject->trySetArgument(exec->vm(), i, descriptor.value());
</span><del>- // ii. If Desc.[[Writable]] is present and its value is false, then
- // 1. Call the [[Delete]] internal method of map passing P and false as arguments.
- if (descriptor.writablePresent() && !descriptor.writable())
- thisObject->tryDeleteArgument(exec->vm(), i);
</del><ins>+
+ // If the property is not deleted and we are using a non-accessor, writable
+ // descriptor, then we are done. The argument continues to be aliased. Note that we
+ // ignore the request to change enumerability. We appear to have always done so, in
+ // cases where the argument was still aliased.
+ // FIXME: https://bugs.webkit.org/show_bug.cgi?id=141952
+ if (descriptor.writable())
+ return true;
</ins><span class="cx"> }
</span><ins>+
+ // If the property is a non-deleted argument, then move it into the base object and then
+ // delete it.
+ JSValue value = thisObject->tryGetArgument(i);
+ ASSERT(value);
+ object->putDirectMayBeIndex(exec, propertyName, value);
+ thisObject->tryDeleteArgument(exec->vm(), i);
</ins><span class="cx"> }
</span><del>- return true;
</del><ins>+
+ // Now just let the normal object machinery do its thing.
+ return Base::defineOwnProperty(object, exec, propertyName, descriptor, shouldThrow);
</ins><span class="cx"> }
</span><span class="cx">
</span><span class="cx"> if (propertyName == exec->propertyNames().length && !thisObject->m_overrodeLength) {
</span></span></pre></div>
<a id="trunkSourceJavaScriptCoretestsstressargumentsbizarrebehaviorjs"></a>
<div class="addfile"><h4>Added: trunk/Source/JavaScriptCore/tests/stress/arguments-bizarre-behavior.js (0 => 180564)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/JavaScriptCore/tests/stress/arguments-bizarre-behavior.js (rev 0)
+++ trunk/Source/JavaScriptCore/tests/stress/arguments-bizarre-behavior.js 2015-02-24 17:08:06 UTC (rev 180564)
</span><span class="lines">@@ -0,0 +1,25 @@
</span><ins>+function foo(x) {
+ Object.defineProperty(arguments, 0, {configurable: true, enumerable: true, writable:true, value:42});
+ return [x, arguments[0], arguments]
+}
+
+var result = foo(1);
+
+if (result[0] !== 42)
+ throw new Error();
+
+if (result[1] !== 42)
+ throw new Error();
+
+if (Array.prototype.join.call(result[2], ",") != "42")
+ throw new Error();
+
+var array = [];
+for (var s in result[2])
+ array.push(s);
+
+if (array.join(",") != "0")
+ throw new Error();
+
+if (Object.keys(result[2]).join(",") != "0")
+ throw new Error();
</ins></span></pre></div>
<a id="trunkSourceJavaScriptCoretestsstressargumentsbizarrebehaviourdisableenumerabilityjs"></a>
<div class="addfile"><h4>Added: trunk/Source/JavaScriptCore/tests/stress/arguments-bizarre-behaviour-disable-enumerability.js (0 => 180564)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/JavaScriptCore/tests/stress/arguments-bizarre-behaviour-disable-enumerability.js (rev 0)
+++ trunk/Source/JavaScriptCore/tests/stress/arguments-bizarre-behaviour-disable-enumerability.js 2015-02-24 17:08:06 UTC (rev 180564)
</span><span class="lines">@@ -0,0 +1,30 @@
</span><ins>+function foo(x) {
+ Object.defineProperty(arguments, 0, {configurable: true, enumerable: false, writable:true, value:42});
+ return [x, arguments[0], arguments]
+}
+
+var result = foo(1);
+
+if (result[0] !== 42)
+ throw new Error();
+
+if (result[1] !== 42)
+ throw new Error();
+
+if (Array.prototype.join.call(result[2], ",") != "42")
+ throw new Error();
+
+var array = [];
+for (var s in result[2])
+ array.push(s);
+
+if (array.join(",") != "0")
+ throw new Error();
+
+if (Object.keys(result[2]).join(",") != "0")
+ throw new Error();
+
+// FIXME: This is totally weird!
+// https://bugs.webkit.org/show_bug.cgi?id=141952
+if (Object.getOwnPropertyDescriptor(result[2], 0).enumerable !== true)
+ throw new Error();
</ins></span></pre></div>
<a id="trunkSourceJavaScriptCoretestsstressargumentscustompropertiesgcjs"></a>
<div class="addfile"><h4>Added: trunk/Source/JavaScriptCore/tests/stress/arguments-custom-properties-gc.js (0 => 180564)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/JavaScriptCore/tests/stress/arguments-custom-properties-gc.js (rev 0)
+++ trunk/Source/JavaScriptCore/tests/stress/arguments-custom-properties-gc.js 2015-02-24 17:08:06 UTC (rev 180564)
</span><span class="lines">@@ -0,0 +1,36 @@
</span><ins>+function makeBaseArguments() {
+ return arguments;
+}
+
+noInline(makeBaseArguments);
+
+function makeArray(length) {
+ var array = new Array(length);
+ for (var i = 0; i < length; ++i)
+ array[i] = 99999;
+ return array;
+}
+
+noInline(makeArray);
+
+function cons(f) {
+ var result = makeBaseArguments();
+ result.f = f;
+ return result;
+}
+
+var array = [];
+for (var i = 0; i < 100000; ++i)
+ array.push(cons(i));
+
+for (var i = 0; i < 1000000; ++i) {
+ var j = (i * 3) % array.length;
+ array[j] = cons(j);
+
+ makeArray(i % 7);
+}
+
+for (var i = 0; i < array.length; ++i) {
+ if (array[i].f != i)
+ throw "Error: bad value of f at " + i + ": " + array[i].f;
+}
</ins></span></pre>
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