debugging a java.lang.VerifyError

Question

I am getting a java.lang.VerifyError, on the page of oracle it says it's thrown because of inconsistencies or security problems. But this can be an awful lot of things and I don't even know what I'm looking for or in which class I should look.

The error message doesn't clarify things either:

java.lang.VerifyError: (class: proto/lua/libraries/ProtoLib$Lib1, method: call signature: ()Lproto/lua/LuaValue;) Wrong return type in function

What inconsistencies should I be on the lookout for? And can anyone tell in what class I should look based on that error?

Any general help/info on the topic of these exceptions would be appreciated too

EDIT: I rewrote much of the Lua Library and until I got this error that worked perfectly fine in every aspect and I use Java SE 6 Update 26

EDIT: Whole error:

java.lang.VerifyError: (class: proto/lua/libraries/ProtoLib$Lib1, method: call signature: ()Lproto/lua/LuaValue;) Wrong return type in function
    at java.lang.Class.getDeclaredConstructors0(Native Method)
    at java.lang.Class.privateGetDeclaredConstructors(Class.java:2389)
    at java.lang.Class.getConstructor0(Class.java:2699)
    at java.lang.Class.newInstance0(Class.java:326)
    at java.lang.Class.newInstance(Class.java:308)
    at proto.lua.libraries.LibFunction.bind(LibFunction.java:169)
    at proto.lua.libraries.LibFunction.bind(LibFunction.java:152)
    at proto.lua.libraries.ProtoLib.call(ProtoLib.java:26)
    at proto.lua.otherstuff.OneArgFunction.call(OneArgFunction.java:66)
    at proto.lua.LuaValue.load(LuaValue.java:1358)
    at proto.lua.RavenLua.standardGlobals(RavenLua.java:100)
    at proto.ProjectPROTO.<clinit>(ProjectPROTO.java:51)
Could not find the main class: proto.ProjectPROTO.  Program will exit.
Exception in thread "main" Java Result: 1

All proto.xxx.xxx.xxx classes are part of the source

EDIT: Well apparently the error was caused since I forgot some @Override annotations, don't know what made them start giving errors though.

Answer 1

What is the full stack trace? It should show that which class is calling that method. Probably the reason is that the code is being executed against a different version of the library that it was compiled against, and there is some incompatible change between those library versions (from the error message it appears to be a different method return type).

If that error is not about any library, but about your own code, then do a clean build. The compiler should produce a compile error about all things which may cause a verify error at runtime. Or if the source code is correct, it should rebuild all the class files correctly.