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<dl class="meta">
<dt>Revision</dt> <dd><a href="http://trac.webkit.org/projects/webkit/changeset/202602">202602</a></dd>
<dt>Author</dt> <dd>sbarati@apple.com</dd>
<dt>Date</dt> <dd>2016-06-28 19:06:22 -0700 (Tue, 28 Jun 2016)</dd>
</dl>
<h3>Log Message</h3>
<pre>Assertion failure or crash when accessing let-variable in TDZ with eval with a function in it that returns let variable
https://bugs.webkit.org/show_bug.cgi?id=158796
<rdar://problem/26984659>
Reviewed by Michael Saboff.
There was a bug where some functions inside of an eval were
omitting a necessary TDZ check. This obviously leads to bad
things because a variable under TDZ is the null pointer.
The eval's bytecode was generated with the correct TDZ set, but
it created all its functions before pushing that TDZ set onto
the stack. That's a mistake. Those functions need to be created with
that TDZ set. The solution is simple, the TDZ set that the eval
is created with needs to be pushed onto the TDZ stack before
the eval creates any functions.
* bytecompiler/BytecodeGenerator.cpp:
(JSC::BytecodeGenerator::BytecodeGenerator):
* tests/stress/variable-under-tdz-eval-tricky.js: Added.
(assert):
(throw.new.Error):
(assert.try.underTDZ):</pre>
<h3>Modified Paths</h3>
<ul>
<li><a href="#trunkSourceJavaScriptCoreChangeLog">trunk/Source/JavaScriptCore/ChangeLog</a></li>
<li><a href="#trunkSourceJavaScriptCorebytecompilerBytecodeGeneratorcpp">trunk/Source/JavaScriptCore/bytecompiler/BytecodeGenerator.cpp</a></li>
</ul>
<h3>Added Paths</h3>
<ul>
<li><a href="#trunkSourceJavaScriptCoretestsstressvariableundertdzevaltrickyjs">trunk/Source/JavaScriptCore/tests/stress/variable-under-tdz-eval-tricky.js</a></li>
</ul>
</div>
<div id="patch">
<h3>Diff</h3>
<a id="trunkSourceJavaScriptCoreChangeLog"></a>
<div class="modfile"><h4>Modified: trunk/Source/JavaScriptCore/ChangeLog (202601 => 202602)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/JavaScriptCore/ChangeLog 2016-06-29 01:52:14 UTC (rev 202601)
+++ trunk/Source/JavaScriptCore/ChangeLog 2016-06-29 02:06:22 UTC (rev 202602)
</span><span class="lines">@@ -1,3 +1,28 @@
</span><ins>+2016-06-28 Saam Barati <sbarati@apple.com>
+
+ Assertion failure or crash when accessing let-variable in TDZ with eval with a function in it that returns let variable
+ https://bugs.webkit.org/show_bug.cgi?id=158796
+ <rdar://problem/26984659>
+
+ Reviewed by Michael Saboff.
+
+ There was a bug where some functions inside of an eval were
+ omitting a necessary TDZ check. This obviously leads to bad
+ things because a variable under TDZ is the null pointer.
+ The eval's bytecode was generated with the correct TDZ set, but
+ it created all its functions before pushing that TDZ set onto
+ the stack. That's a mistake. Those functions need to be created with
+ that TDZ set. The solution is simple, the TDZ set that the eval
+ is created with needs to be pushed onto the TDZ stack before
+ the eval creates any functions.
+
+ * bytecompiler/BytecodeGenerator.cpp:
+ (JSC::BytecodeGenerator::BytecodeGenerator):
+ * tests/stress/variable-under-tdz-eval-tricky.js: Added.
+ (assert):
+ (throw.new.Error):
+ (assert.try.underTDZ):
+
</ins><span class="cx"> 2016-06-28 Michael Saboff <msaboff@apple.com>
</span><span class="cx">
</span><span class="cx"> REGRESSION (r200946): Improper backtracking from last alternative in sticky patterns
</span></span></pre></div>
<a id="trunkSourceJavaScriptCorebytecompilerBytecodeGeneratorcpp"></a>
<div class="modfile"><h4>Modified: trunk/Source/JavaScriptCore/bytecompiler/BytecodeGenerator.cpp (202601 => 202602)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/JavaScriptCore/bytecompiler/BytecodeGenerator.cpp 2016-06-29 01:52:14 UTC (rev 202601)
+++ trunk/Source/JavaScriptCore/bytecompiler/BytecodeGenerator.cpp 2016-06-29 02:06:22 UTC (rev 202602)
</span><span class="lines">@@ -619,6 +619,8 @@
</span><span class="cx">
</span><span class="cx"> m_codeBlock->setNumParameters(1);
</span><span class="cx">
</span><ins>+ pushTDZVariables(*parentScopeTDZVariables, TDZCheckOptimization::DoNotOptimize);
+
</ins><span class="cx"> emitEnter();
</span><span class="cx">
</span><span class="cx"> allocateAndEmitScope();
</span><span class="lines">@@ -641,8 +643,6 @@
</span><span class="cx"> if (evalNode->usesSuperCall() || evalNode->usesNewTarget())
</span><span class="cx"> m_newTargetRegister = addVar();
</span><span class="cx">
</span><del>- pushTDZVariables(*parentScopeTDZVariables, TDZCheckOptimization::DoNotOptimize);
-
</del><span class="cx"> if (codeBlock->isArrowFunctionContext() && (evalNode->usesThis() || evalNode->usesSuperProperty()))
</span><span class="cx"> emitLoadThisFromArrowFunctionLexicalEnvironment();
</span><span class="cx">
</span></span></pre></div>
<a id="trunkSourceJavaScriptCoretestsstressvariableundertdzevaltrickyjs"></a>
<div class="addfile"><h4>Added: trunk/Source/JavaScriptCore/tests/stress/variable-under-tdz-eval-tricky.js (0 => 202602)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/JavaScriptCore/tests/stress/variable-under-tdz-eval-tricky.js (rev 0)
+++ trunk/Source/JavaScriptCore/tests/stress/variable-under-tdz-eval-tricky.js 2016-06-29 02:06:22 UTC (rev 202602)
</span><span class="lines">@@ -0,0 +1,60 @@
</span><ins>+function assert(b) {
+ if (!b)
+ throw new Error("Bad!")
+}
+
+
+{
+ let threw = false;
+ try {
+ let underTDZ = {
+ prop: eval("function pleaseTDZMe(){ return underTDZ; }; pleaseTDZMe();")
+ };
+ } catch(e) {
+ threw = e instanceof ReferenceError;
+ }
+ assert(threw);
+}
+
+{
+ let threw = false;
+ try {
+ const underTDZ = {
+ prop: eval("function pleaseTDZMe(){ return underTDZ; }; pleaseTDZMe();")
+ };
+ } catch(e) {
+ threw = e instanceof ReferenceError;
+ }
+ assert(threw);
+}
+
+{
+ let threw = false;
+ try {
+ class underTDZ extends eval("function pleaseTDZMe() { return underTDZ; }; pleaseTDZMe()") { };
+ } catch(e) {
+ threw = e instanceof ReferenceError;
+ }
+ assert(threw);
+}
+
+{
+ let threw = false;
+ try {
+ let b = {a: eval("function b(){ return b; }"), b: (1, eval)("(b())")};
+ } catch(e) {
+ threw = e instanceof ReferenceError;
+ }
+ assert(threw);
+}
+
+{
+ let threw = false;
+ try {
+ let {b} = {a: eval("function b(){ return b; }"), b: (1, eval)("print(b())")};
+ } catch(e) {
+ threw = e instanceof ReferenceError;
+ }
+ assert(threw);
+}
+
</ins></span></pre>
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