Re: A complete list of JDK classes which CheckClassAdapter fails (bug?)

Sai Zhang wrote:
> Hi,
> 
> I am using ASM to instrument the whole JDK, but found the 
> CheckClassAdapter seems
> to be not so "reliable". It fails when verifying the bytecode of 
> *untouched *JDK classes (in rt.jar).
> 
> There could be two possibilities:
> (1) a bug in CheckClassAdapter
> (2) the JDK classes are not valid themselves (which might not be the 
> case, I could be wrong.)
> 
> We can reproduce it by simply using the following command:
> 
> |java -cp asm-all.jar org.objectweb.asm.util.CheckClassAdapter 
> org/domain/package/YourClass.class|
> 
> Any one has ideas on this point? Any comments and suggestion are highly 
> appreciated.

for the java.awt.List case, it seems the problem comes from the merge of two interface types on the stack. One branch of a "if" pushes a java.awt.ActionListener. The other branch pushes a java.awt.ItemListener. ASM merges this using the common *super class*, which is Object (the common super-interface is java.awt.EventListener, the expected type). The problem is that I never saw any rule in the JVM specification to compute such a common super interface type when merging stack frames.

Eric

Error at instruction 25: Argument 1: expected Ljava/util/EventListener;, but found R

00000 List Class .               :                 :     ACONST_NULL
00001 List Class .               : Lnull;          :     ASTORE 2
00002 List Class Lnull;          :                 :     ALOAD 1
00003 List Class Lnull;          : Class           :     LDC Ljava/awt/event/ActionListener;.class
00004 List Class Lnull;          : Class Class     :     IF_ACMPNE L0
00005 List Class Lnull;          :                 :     ALOAD 0
00006 List Class Lnull;          : List            :     GETFIELD java/awt/List.actionListener : Ljava/awt/event/ActionListener;
00007 List Class Lnull;          : ActionListener  :     ASTORE 2
00008 List Class ActionListener  :                 :     GOTO L1
00009 List Class Lnull;          :                 :    L0
00010 List Class Lnull;          :                 :     ALOAD 1
00011 List Class Lnull;          : Class           :     LDC Ljava/awt/event/ItemListener;.class
00012 List Class Lnull;          : Class Class     :     IF_ACMPNE L2
00013 List Class Lnull;          :                 :     ALOAD 0
00014 List Class Lnull;          : List            :     GETFIELD java/awt/List.itemListener : Ljava/awt/event/ItemListener;
00015 List Class Lnull;          : ItemListener    :     ASTORE 2
00016 List Class ItemListener    :                 :     GOTO L1
00017 List Class Lnull;          :                 :    L2
00018 List Class Lnull;          :                 :     ALOAD 0
00019 List Class Lnull;          : List            :     ALOAD 1
00020 List Class Lnull;          : List Class      :     INVOKESPECIAL java/awt/Component.getListeners (Ljava/lang/Class;)[Ljava/util/EventListener;
00021 List Class Lnull;          : EventListener   :     ARETURN
00022 List Class R               :                 :    L1
00023 List Class R               :                 :     ALOAD 2
00024 List Class R               : R               :     ALOAD 1
00025 List Class R               : R Class         :     INVOKESTATIC java/awt/AWTEventMulticaster.getListeners (Ljava/util/EventListener;Ljava/lang/Class;)[Ljava/util/EventListener;
00026 List Class ItemListener    : EventListener   :     ARETURN

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