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From Vincent Marquez <vmarq...@totemworks.com>
Subject Problems with Try/Catch Blocks
Date Thu, 17 Feb 2005 10:16:42 GMT

My problem is, while i'm modifying a method, if the method i'm modifying 
has a try/catch block, I get a "inconsistant stack height" error.   It 
seems this only occurs if the Try/Catch block is directly around the 
part i'm modifying.  Currently, i'm replacing a constructor from once 
class type to another.  It works perfectly except when there are 
Try/Catch blocks.  For example, if I have

1:    public static void main( String [] args ) {
2:        System.out.println( "test" );
3:        System.out.println( "anotherr test");
4:        Shape shape = new Shape();
5:        System.out.println( "final test" );
6:     }

There isn't a problem if the try/catch is around line 2 and 3.  Only if 
it encapsulates line 4, or anything after,  will there be the error.   
For legal reasons i'm unable to show all my actual code so I contrived a 
very similar example of our insturmenation method that is below.   If 
i'm doing anything wrong/stupid let me know.  If you see other problems 
with my code, feel free to let me know also, i'm always looking for ways 
to improve.  Thanks for any help/suggestions and MUCH thanks to whoever 
can solve my problem. 


--vince

protected void replaceConstructor( ClassGen cg, String original_class, 
String new_class ) {
 
        boolean refresh = false;
        ConstantPoolGen cp_gen = cg.getConstantPool();
        ConstantPool cp        = cp_gen.getConstantPool();
        InstructionFactory factory = new InstructionFactory( cg , cp_gen );

        Method [] methods = cg.getMethods();
        for ( int x=0; x<methods.length; x++ ) {
            refresh = false;
            MethodGen method_gen = new MethodGen( methods[x], 
cg.getJavaClass().getClassName(), cp_gen );
            Iterator i = method_gen.getInstructionList().iterator();
        
  
            while ( i.hasNext() ) {
                InstructionHandle handle = ( InstructionHandle )i.next();

                if ( handle.getInstruction() instanceof INVOKESPECIAL && 
( ( INVOKESPECIAL )handle.getInstruction() ).getClassName( cp_gen 
).equals( original_class ) && ( ( INVOKESPECIAL )handle.getInstruction() 
).getMethodName( cp_gen ).equals( "<init>" ) ) {
                    try {
                        INVOKESPECIAL invk = ( INVOKESPECIAL 
)handle.getInstruction();
                                      
method_gen.getInstructionList().insert( invk, factory.createInvoke(
                                    new_class,
                                    "name",
                                    new ObjectType( original_class ),
                                    invk.getArgumentTypes( cp_gen ),
                                    Constants.INVOKESTATIC) );

                        // Delete the old method
                        method_gen.getInstructionList().delete( invk );
                        refresh = true;
                    } catch ( 
org.apache.bcel.generic.TargetLostException e ) {
                        Log.write( "Error", + e.toString() );
                    }
                }
            }
            if ( refresh ) {
                  method_gen.stripAttributes( false );
                method_gen.setMaxStack();
                method_gen.setMaxLocals();
               cg.replaceMethod( methods[x], method_gen.getMethod() );
            }
           }

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