<html>
    <head>
      <base href="https://bugs.webkit.org/" />
    </head>
    <body><table border="1" cellspacing="0" cellpadding="8">
        <tr>
          <th>Bug ID</th>
          <td><a class="bz_bug_link 
          bz_status_NEW "
   title="NEW - jsc-layout-tests.yaml/js/script-tests/class-syntax-default-constructor.js.* fails when run with JSC_validateBytecode=true."
   href="https://bugs.webkit.org/show_bug.cgi?id=165829">165829</a>
          </td>
        </tr>

        <tr>
          <th>Summary</th>
          <td>jsc-layout-tests.yaml/js/script-tests/class-syntax-default-constructor.js.* fails when run with JSC_validateBytecode=true.
          </td>
        </tr>

        <tr>
          <th>Classification</th>
          <td>Unclassified
          </td>
        </tr>

        <tr>
          <th>Product</th>
          <td>WebKit
          </td>
        </tr>

        <tr>
          <th>Version</th>
          <td>WebKit Local Build
          </td>
        </tr>

        <tr>
          <th>Hardware</th>
          <td>Unspecified
          </td>
        </tr>

        <tr>
          <th>OS</th>
          <td>Unspecified
          </td>
        </tr>

        <tr>
          <th>Status</th>
          <td>NEW
          </td>
        </tr>

        <tr>
          <th>Severity</th>
          <td>Normal
          </td>
        </tr>

        <tr>
          <th>Priority</th>
          <td>P2
          </td>
        </tr>

        <tr>
          <th>Component</th>
          <td>JavaScriptCore
          </td>
        </tr>

        <tr>
          <th>Assignee</th>
          <td>webkit-unassigned&#64;lists.webkit.org
          </td>
        </tr>

        <tr>
          <th>Reporter</th>
          <td>mark.lam&#64;apple.com
          </td>
        </tr></table>
      <p>
        <div>
        <pre>Running ...
    $ JSC_validateBytecode=1 ./Tools/Scripts/run-javascriptcore-tests --debug --no-build
... on a debug build of 209727 produces:

jsc-layout-tests.yaml/js/script-tests/class-syntax-default-constructor.js.layout: Tests for ES6 class syntax default constructor
jsc-layout-tests.yaml/js/script-tests/class-syntax-default-constructor.js.layout: 
jsc-layout-tests.yaml/js/script-tests/class-syntax-default-constructor.js.layout: On success, you will see a series of &quot;PASS&quot; messages, followed by &quot;TEST COMPLETE&quot;.
jsc-layout-tests.yaml/js/script-tests/class-syntax-default-constructor.js.layout: 
jsc-layout-tests.yaml/js/script-tests/class-syntax-default-constructor.js.layout: 
jsc-layout-tests.yaml/js/script-tests/class-syntax-default-constructor.js.layout: PASS new A instanceof A
jsc-layout-tests.yaml/js/script-tests/class-syntax-default-constructor.js.layout: PASS A():::TypeError: Cannot call a class constructor without |new|
jsc-layout-tests.yaml/js/script-tests/class-syntax-default-constructor.js.layout: PASS A.prototype.constructor instanceof Function
jsc-layout-tests.yaml/js/script-tests/class-syntax-default-constructor.js.layout: PASS A.prototype.constructor.name:::&quot;A&quot;
jsc-layout-tests.yaml/js/script-tests/class-syntax-default-constructor.js.layout: PASS new B instanceof A; new B instanceof A
jsc-layout-tests.yaml/js/script-tests/class-syntax-default-constructor.js.layout: ASSERTION FAILED: i + 1 &lt; basicBlocks.size()
jsc-layout-tests.yaml/js/script-tests/class-syntax-default-constructor.js.layout: /Volumes/Data/ws2/OpenSource/Source/JavaScriptCore/bytecode/BytecodeBasicBlock.cpp(179) : static void JSC::BytecodeBasicBlock::computeImpl(Block *, Instruction *, unsigned int, Vector&lt;std::unique_ptr&lt;BytecodeBasicBlock&gt; &gt; &amp;) [Block = JSC::CodeBlock, Instruction = JSC::Instruction]
jsc-layout-tests.yaml/js/script-tests/class-syntax-default-constructor.js.layout: 1   0x10e695ded WTFCrash
jsc-layout-tests.yaml/js/script-tests/class-syntax-default-constructor.js.layout: 2   0x10d67eae9 void JSC::BytecodeBasicBlock::computeImpl&lt;JSC::CodeBlock, JSC::Instruction&gt;(JSC::CodeBlock*, JSC::Instruction*, unsigned int, WTF::Vector&lt;std::__1::unique_ptr&lt;JSC::BytecodeBasicBlock, std::__1::default_delete&lt;JSC::BytecodeBasicBlock&gt; &gt;, 0ul, WTF::CrashOnOverflow, 16ul&gt;&amp;)
jsc-layout-tests.yaml/js/script-tests/class-syntax-default-constructor.js.layout: 3   0x10d67db0b JSC::BytecodeBasicBlock::compute(JSC::CodeBlock*, JSC::Instruction*, unsigned int, WTF::Vector&lt;std::__1::unique_ptr&lt;JSC::BytecodeBasicBlock, std::__1::default_delete&lt;JSC::BytecodeBasicBlock&gt; &gt;, 0ul, WTF::CrashOnOverflow, 16ul&gt;&amp;)
jsc-layout-tests.yaml/js/script-tests/class-syntax-default-constructor.js.layout: 4   0x10d6e4a13 JSC::BytecodeGraph&lt;JSC::CodeBlock&gt;::BytecodeGraph(JSC::CodeBlock*, WTF::RefCountedArray&lt;JSC::Instruction&gt;&amp;)
jsc-layout-tests.yaml/js/script-tests/class-syntax-default-constructor.js.layout: 5   0x10d6e1e45 JSC::BytecodeGraph&lt;JSC::CodeBlock&gt;::BytecodeGraph(JSC::CodeBlock*, WTF::RefCountedArray&lt;JSC::Instruction&gt;&amp;)
jsc-layout-tests.yaml/js/script-tests/class-syntax-default-constructor.js.layout: 6   0x10d6e1dec JSC::BytecodeLivenessAnalysis::BytecodeLivenessAnalysis(JSC::CodeBlock*)
jsc-layout-tests.yaml/js/script-tests/class-syntax-default-constructor.js.layout: 7   0x10d6e1ead JSC::BytecodeLivenessAnalysis::BytecodeLivenessAnalysis(JSC::CodeBlock*)
jsc-layout-tests.yaml/js/script-tests/class-syntax-default-constructor.js.layout: 8   0x10d733d64 JSC::CodeBlock::validate()
jsc-layout-tests.yaml/js/script-tests/class-syntax-default-constructor.js.layout: 9   0x10e4c67c9 JSC::ScriptExecutable::prepareForExecutionImpl(JSC::VM&amp;, JSC::JSFunction*, JSC::JSScope*, JSC::CodeSpecializationKind, JSC::CodeBlock*&amp;)
jsc-layout-tests.yaml/js/script-tests/class-syntax-default-constructor.js.layout: 10  0x10df340e0 JSC::JSObject* JSC::ScriptExecutable::prepareForExecution&lt;JSC::FunctionExecutable&gt;(JSC::VM&amp;, JSC::JSFunction*, JSC::JSScope*, JSC::CodeSpecializationKind, JSC::CodeBlock*&amp;)
jsc-layout-tests.yaml/js/script-tests/class-syntax-default-constructor.js.layout: 11  0x10e1d3a64 JSC::LLInt::setUpCall(JSC::ExecState*, JSC::Instruction*, JSC::CodeSpecializationKind, JSC::JSValue, JSC::LLIntCallLinkInfo*)
jsc-layout-tests.yaml/js/script-tests/class-syntax-default-constructor.js.layout: 12  0x10e1d2b83 JSC::LLInt::genericCall(JSC::ExecState*, JSC::Instruction*, JSC::CodeSpecializationKind)
jsc-layout-tests.yaml/js/script-tests/class-syntax-default-constructor.js.layout: 13  0x10e1d2a73 llint_slow_path_call
jsc-layout-tests.yaml/js/script-tests/class-syntax-default-constructor.js.layout: 14  0x10e1e1083 llint_entry
jsc-layout-tests.yaml/js/script-tests/class-syntax-default-constructor.js.layout: 15  0x10e1d995e vmEntryToJavaScript
jsc-layout-tests.yaml/js/script-tests/class-syntax-default-constructor.js.layout: 16  0x10dfb8a92 JSC::JITCode::execute(JSC::VM*, JSC::ProtoCallFrame*)
jsc-layout-tests.yaml/js/script-tests/class-syntax-default-constructor.js.layout: 17  0x10df3006f JSC::Interpreter::execute(JSC::EvalExecutable*, JSC::ExecState*, JSC::JSValue, JSC::JSScope*)
jsc-layout-tests.yaml/js/script-tests/class-syntax-default-constructor.js.layout: 18  0x10df2f007 JSC::eval(JSC::ExecState*)
jsc-layout-tests.yaml/js/script-tests/class-syntax-default-constructor.js.layout: 19  0x10e1d3673 llint_slow_path_call_eval
jsc-layout-tests.yaml/js/script-tests/class-syntax-default-constructor.js.layout: 20  0x10e1e1926 llint_entry
jsc-layout-tests.yaml/js/script-tests/class-syntax-default-constructor.js.layout: 21  0x10e1e1095 llint_entry
jsc-layout-tests.yaml/js/script-tests/class-syntax-default-constructor.js.layout: 22  0x10e1d995e vmEntryToJavaScript
jsc-layout-tests.yaml/js/script-tests/class-syntax-default-constructor.js.layout: 23  0x10dfb8a92 JSC::JITCode::execute(JSC::VM*, JSC::ProtoCallFrame*)
jsc-layout-tests.yaml/js/script-tests/class-syntax-default-constructor.js.layout: 24  0x10df33464 JSC::Interpreter::execute(JSC::ProgramExecutable*, JSC::ExecState*, JSC::JSObject*)
jsc-layout-tests.yaml/js/script-tests/class-syntax-default-constructor.js.layout: 25  0x10d7c095d JSC::evaluate(JSC::ExecState*, JSC::SourceCode const&amp;, JSC::JSValue, WTF::NakedPtr&lt;JSC::Exception&gt;&amp;)
jsc-layout-tests.yaml/js/script-tests/class-syntax-default-constructor.js.layout: 26  0x10d226061 runWithScripts(GlobalObject*, WTF::Vector&lt;Script, 0ul, WTF::CrashOnOverflow, 16ul&gt; const&amp;, WTF::String const&amp;, bool, bool, bool)
jsc-layout-tests.yaml/js/script-tests/class-syntax-default-constructor.js.layout: 27  0x10d21dc3a runJSC(JSC::VM*, CommandLine)
jsc-layout-tests.yaml/js/script-tests/class-syntax-default-constructor.js.layout: 28  0x10d21c79d jscmain(int, char**)
jsc-layout-tests.yaml/js/script-tests/class-syntax-default-constructor.js.layout: 29  0x10d21c6ee main
jsc-layout-tests.yaml/js/script-tests/class-syntax-default-constructor.js.layout: 30  0x7fffb4298255 start
jsc-layout-tests.yaml/js/script-tests/class-syntax-default-constructor.js.layout: test_script_25656: line 2: 62134 Segmentation fault: 11  ( &quot;$&#64;&quot; ../../../../.vm/JavaScriptCore.framework/Resources/jsc --useFTLJIT\=false --useFunctionDotArguments\=true --maxPerThreadStackUsage\=1572864 --testTheFTL\=true --useFTLJIT\=true resources/standalone-pre.js class-syntax-default-constructor.js resources/standalone-post.js )
jsc-layout-tests.yaml/js/script-tests/class-syntax-default-constructor.js.layout: ERROR: Unexpected exit code: 139

Basically, we're seeing an assertion failure:
    ASSERTION FAILED: i + 1 &lt; basicBlocks.size()</pre>
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