Support for Javaflow bytecode pattern ------------------------------------- Key: JASSIST-234 URL: https://issues.jboss.org/browse/JASSIST-234 Project: Javassist Issue Type: Patch Affects Versions: 3.18.2-GA Reporter: Shigeru Chiba Assignee: Shigeru Chiba Fix For: 3.19.0-GA The Apache Javaflow project instruments class files to provide its Continuation capability. One of the bytecode patterns it generates to handle Category 2 parameters is: NEW DUP DUP2_X2 POP2 Unfortunately, when Javassist sees this pattern when moving instructions, it recognizes the NEW DUP and removes it in order to do the move. However, this leaves the DUP2_X2 POP2 abandoned which leads to stack corruption and javassist throwing an exception due to a negative stack height. Given this involves Category 2 operands, there is not much short of a complete rearchitecting that can be done in Javaflow to accommodate the existing Javassist patterns for NEW. Therefore, I ask the the above bytecode pattern be added to the javassist.expr.NewExpr.canReplace() method. I will submit a patch with the proposed change. Originally reported by Baron Roberts at: https://github.com/jboss-javassist/javassist/pull/21