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POJava inner class inconsistency between descriptor and signature attribute? (class file)
 

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    <p>I'm trying to understand if there's a reason in the spec for the discrepany between java descriptors and signatures for inner classes. (I'm looking directly at the content of the class files here, but I use javap to illustrate).</p> <p>( n.b. I have tried this on JDK 1.6.0_33 and 1.7.0_05, both have the same issue <em>when viewed with javap from Java 7</em> - java 6's javap doesn't seem to show any generic signature info, as per Sean's answer below. )</p> <p>Update : Thanks to those discussing - my take is</p> <ul> <li>The descriptor (which doesn't contain generic information) is correct. </li> <li>The signature (which is an attribute of the method, and does contain generic information) is incorrect. The relevant ConstPool entry for SIGNATURE of the &lt;init&gt; method is " ConstantUTF8[(Ljava/util/list&lt;TE;&gt;)V] "</li> <li>Javap in Java 6 doesn't LOOK at the signature, just the descriptor. (My guess!)</li> </ul> <p>In case anyone wonders, I hit this without using JAVAP, just looking at the class files myself, I am only using javap to show it. (so it's unlikely to be a javap bug).</p> <p>Consider:</p> <pre><code>public class InnerClassTest1 { public int getX() { return new Inner1(new ArrayList&lt;String&gt;()).getX(4); } public class Inner1 { private final List arg; public Inner1(List arg) { this.arg = arg; }.... </code></pre> <p>vs</p> <pre><code>public class InnerClassTest2 { public int getX() { return new Inner1(new ArrayList&lt;String&gt;()).getX(4); } public class Inner1&lt;E&gt; { private final List&lt;E&gt; arg; public Inner1(List&lt;E&gt; arg) { this.arg = arg; }..... </code></pre> <p>If you look at the output of javap -cs on the inner classes, they're surprisingly different!</p> <p>public org.benf.cfr.tests.InnerClassTest1$Inner1(<strong>org.benf.cfr.tests.InnerClassTest1,</strong> java.util.List); Signature: (Lorg/benf/cfr/tests/InnerClassTest1;Ljava/util/List;)V</p> <p>vs</p> <p>public org.benf.cfr.tests.InnerClassTest2$Inner1(java.util.List&lt;E&gt;); Signature: (Lorg/benf/cfr/tests/InnerClassTest2;Ljava/util/List;)V</p> <p>... <em>the one which uses generics is missing the implicit parameter for the outer class!</em> (it's correctly present in InnerClassTest1).</p> <p>I can't find anything in the class file documentation to explain this - does anyone know why this might be?</p> <p>Thanks!</p> <p>Lee.</p> <hr> <p>Update - </p> <p>I've placed example files at <a href="http://www.benf.org/files/innerClassTest.tgz" rel="nofollow" title="example files &#40;tgz&#41;">http://www.benf.org/files/innerClassTest.tgz</a></p> <p>Given Sean's answer below, I tried using javap on java 6, and I saw identical output for both, with no generic information - this leads me to believe that java 6's javap is not displaying full signature information?</p> <p>The exact output I get using javap on 1.7.0_05-b06 is</p> <pre><code>public class org.benf.cfr.tests.InnerClassTest2$Inner1&lt;E&gt; { final org.benf.cfr.tests.InnerClassTest2 this$0; Signature: Lorg/benf/cfr/tests/InnerClassTest2; public org.benf.cfr.tests.InnerClassTest2$Inner1(java.util.List&lt;E&gt;); Signature: (Lorg/benf/cfr/tests/InnerClassTest2;Ljava/util/List;)V Code: 0: aload_0 1: aload_1 2: putfield #1 // Field this$0:Lorg/benf/cfr/tests/InnerClassTest2; 5: aload_0 6: invokespecial #2 // Method java/lang/Object."&lt;init&gt;":()V 9: aload_0 10: aload_2 11: putfield #3 // Field arg:Ljava/util/List; 14: return public int getX(int); Signature: (I)I Code: 0: iconst_2 1: ireturn } </code></pre>
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    1. COPlease, specify JDK details
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    2. COUpdated, thanks.
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    3. COCould you post the actual class files? That would at least narrow it down to a compiler problem vs a disassembler problem.
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