bugfix.txt

Bug in OpenJDK from 28/02:
- I downloaded the latest OpenJDK version from http://download.java.net/openjdk/jdk6/
	- Located at: http://download.java.net/openjdk/jdk6/promoted/b22/openjdk-6-src-b22-28_feb_2011.tar.gz
	- Checksums: http://download.java.net/openjdk/jdk6/promoted/b22/openjdk-6-src-b22-28_feb_2011.md5

- After quite a long time, I found the javac source code and imported the langtools/javac/ into my IntelliJ IDEA IDE
- I compiled it
- Used it to compile some simple HelloWorld classes
	-> Worked
- Used it to compile itself 
	-> Throw NullPointerException in Lower.cs
	-> It turns out that Enums cannot compile anymore


- The Lower class is used to add statements that are assumed to be present by the programmer, to keep the code shorter and more consistent
- Enums are one of many things that need quite a bit of extra code, emitted
- The problem was caused by enum ctors:
	- The Lower class adds 2 additional parameters and arguments to every ctor definition and invocation: The name and ordinal of each enum member
	- Those arguments are then passed to any super(...) or this(...) call of all enums in order to, eventually, invoke the Enum(String, int) ctor
	- The Lower class visits the super(...) and this(...) invocations in the Lower.visitApply() method
	- It tried to box arguments of the invocation in the Lower.boxArgs method 
	- The underlying ctors already have the parameters but the name and ordinal arguments have not been added to the invocation yet (they are added just a little bit later)
	- Lower.boxArgs(...) iterates over all parameters of the method/ctor and assumes the invocation to have at least as many arguments, without verification
	- But since their are less arguments than parameters, the boxArgs method tries to read beyond the end of the argument list and throws a NullPointerException

- I fixed it by removing the two artifical parameters from the list of parameters given to the boxArgs method, since they don't require any boxing