RE: VerifyError when compiling jetty

[Andrew Haley <aph at redhat dot com>]

Bjarni Thorisson writes:
 > Hello, and thanks for the quick reply.
 > 
 > Below is a simple class you can compile into bytecode with gcj and try to
 > run it. Then this error should occurr:
 > 
 > <--------------------clip----------------------------->
 > Exception in thread "main" java.lang.VerifyError: (class: Smu$Foo, method:
 > run signature: ()V) Illegal use of nonvirtual function call
 >         at Smu.start(Smu.java:28)
 >         at Smu.main(Smu.java:13)
 > <-------------------/clip----------------------------->

I can confirm this.

We generate the same code for Smu.start.  

Looking at Smu$Foo:

Method name:"run" public Signature: 17=()void                                  Method name:"run" public Signature: 9=()void						 
Attribute "Code", length:115, max_stack:2, max_locals:4, code_length:55	       Attribute "Code", length:116, max_stack:2, max_locals:3, code_length:56			 
  0: goto 20								         0: aload_0										 
  3: ldc2_w #1=<Long 1000>						         1: getfield #12=<Field Smu$Foo.this$0 Smu>						 
  6: invokestatic #3=<Method java.lang.Thread.sleep (long)void>		         4: invokevirtual #18=<Method Smu.isStarted ()boolean>					 
  9: aload_0								         7: ifeq 31										 
 10: getfield #4=<Field Smu$Foo.this$0 Smu>				        10: sipush 1000									 
 13: invokestatic #5=<Method Smu.access$000 (Smu)void>			        13: i2l										 
 16: goto 20								        14: invokestatic #22=<Method java.lang.Thread.sleep (long)void>			 
 19: astore_1								        17: aload_0										 
 20: aload_0								        18: getfield #12=<Field Smu$Foo.this$0 Smu>						 
 21: getfield #4=<Field Smu$Foo.this$0 Smu>				        21: invokespecial #25=<Method Smu.doFoo ()void>					 
 24: invokevirtual #7=<Method Smu.isStarted ()boolean>			        24: goto 28										 
 27: ifne 3								        27: astore_1										 
 30: jsr 42								        28: goto 0										 
 33: goto 54								        31: jsr 43										 
 36: astore_2								        34: goto 55										 
 37: jsr 42								        37: astore_2										 
 40: aload_2								        38: jsr 43										 
 41: athrow								        41: aload_2										 
 42: astore_3								        42: athrow										 
 43: aload_0								        43: astore_1										 
 44: getfield #4=<Field Smu$Foo.this$0 Smu>				        44: aload_0										 
 47: aconst_null							        45: getfield #12=<Field Smu$Foo.this$0 Smu>						 
 48: invokestatic #8=<Method Smu.access$102 (Smu,Smu$Foo)Smu$Foo>	        48: aconst_null									 
 51: pop								        49: invokestatic #29=<Method Smu.access$1 (Smu,Smu$Foo)Smu$Foo>			 
 52: ret 3								        52: pop										 
 54: return								        53: ret 1										 
                                                                                55: return
                                                                                        
IBMJava2-131/bin/javac is on the left, we are on the right.  javac
calls Smu.access$100 with invokestatic, whereas we call Smu.doFoo with
invokespecial.  Let's look at Smu.access$000:

Method name:"access$000" static Signature: 32=(Smu)void
Attribute "Code", length:29, max_stack:1, max_locals:1, code_length:5
  0: aload_0
  1: invokespecial #2=<Method Smu.doFoo ()void>
  4: return
Attribute "LineNumberTable", length:6, count: 1
  line: 1 at pc: 0
Attribute "Synthetic", length:0

So, Smu.access$000 is a thunk that javac generates in order to enable
inner classes to access methods in the enclosing class.  AFAICS we
aren't doing that in this case.

This is illegal code on our part, because we're not allowed to use
invokepsecial on a private method.  We should generate an access
method for Smu.doFoo and use it.

Andrew.