FULL PRODUCT VERSION :
javac 1.7.0_09

java version " 1.7.0_09 "
Java(TM) SE Runtime Environment (build 1.7.0_09-b05)
Java HotSpot(TM) 64-Bit Server VM (build 23.5-b02, mixed mode)

ADDITIONAL OS VERSION INFORMATION :
Microsoft Windows [Version 6.1.7601]
Microsoft Windows [Version 5.2.3790]

A DESCRIPTION OF THE PROBLEM :
If a base class (that is, a class that is itself extended), when extending a genericized class, incorrectly specifies the generics arity of the super class, javac will hang when compiling a class that extends the incorrect base class.

  To demonstrate this, create a class that extends HashMap, but only specifies a single generic parameter for HashMap (which should have two): public class BadHashMap<T> extends HashMap<T> { }. The compiler will correctly flag this as an error. However, if another class extends BadHashMap -- e.g., public class ExtendedBadHashMap<T> extends BadHashMap<T> { } -- javac will flag the error in BadHashMap but then go into an infinite loop, pegging the CPU.

REGRESSION. Last worked in version 6u31

STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
Create two classes in a directory X:

public class BadHashMap<T> extends java.util.HashMap<T> { }
public class ExtendedBadHashMap<T> extends BadHashMap<T> { }

Using javac v. 1.7, at a shell/command prompt in directory X type:

javac *.java

EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
The compiler should print an error about the wrong number of generic arguments to HashMap and exit.
ACTUAL -
The compiler does print an error about wrong number of arguments for HashMap, but rather than exiting the javac process hangs and pegs the CPU.

ERROR MESSAGES/STACK TRACES THAT OCCUR :
None -- the process just hangs.

REPRODUCIBILITY :
This bug can be reproduced always.

---------- BEGIN SOURCE ----------
In file BadHashMap.java:
public class BadHashMap<T> extends java.util.HashMap<T> { }

In file ExtendedBadHashMap.java:
public class ExtendedBadHashMap<T> extends BadHashMap<T> { }
---------- END SOURCE ----------

CUSTOMER SUBMITTED WORKAROUND :
  Fix the problem in the source code.