It would be great if javap had a 'plugin' which allowed verification of 
underlying bytecode, which could be ran in isolation. This could be an 
useful tool to diagnose verifier error in the VM and, at the same time, 
to get better output out of the verification process. Most bytecode APIs 
do have some verification tool - ASM one is called CheckClassAdapter:

http://asm.ow2.org/asm40/javadoc/user/org/objectweb/asm/util/CheckClassAdapter.html

while BCEL one is called Verifier:

https://commons.apache.org/proper/commons-bcel/apidocs/org/apache/bcel/verifier/Verifier.html

The verifier could be implemented either on top of javap - or, maybe, on 
top of the new bytecode API, whichever is easier.