How safe is it to use -XX:-UseSplitVerifier?

Question

There are known compatibility issues with JDK7 compiled code using instrumentation. As for http://www.oracle.com/technetwork/java/javase/compatibility-417013.html

Answer 1

Yes -- it's safe. As Judebert says, it just slows class loading slightly.

To add a little more info: What exactly is a StackMap Table? Well, the Bytecode verifier needs to make two passes over the code in the class file to validate proper types of data are being passed around and used. The first pass, which is the slower one, does flow analysis of all the code's branches to see what type of data could be on the stack at each bytecode instruction. The second pass looks at each instruction to see if it can validly operate on all those types.

Here's the key: the compiler already has all the information at hand that the first pass generates - so (in Java 6 & 7) it stores it in a StackMap table in the class file.

This speeds up class loading because the class loader doesn't have to do that first pass. That's why it's called a Split Verifier, because the work is split between the compiler and the runtime loading mechanism. When you use the -XX:-UseSplitVerifier option, you tell Java to do both passes at class load time (and to ignore any StackMap table). Many products (like profilers that modify bytecode at load time) did not know about the StackMap table initially, so when they modified classes at load time, the StackMap table from the compiler was out of date and caused errors.

SO, to summarize, the -XX:-UseSplitVerifier option slows class loading. It does not affect security, runtime performance or functionality.