RE: Jimple and bytecode length

[Stephen Cheng <scheng@clear.net.nz>]

When java bytecode is generated from Jimple instructions, the bytecode
sequence may be too long and breaks the method code length limit specified
by JVM spec (65535 bytes). I can writing a code transformer using Soot to
add additional Jimple instructions to methods in a classfile. I need to make
sure that the modified class file is still legal. Is there any easy way I
can easily estimate the bytecode size of the method from the Jimple
instructions?

I have thought of a few possible solutions, but none of them struck me as a
good idea:
1. Get Soot to actually generate the bytecode sequence, and fail if the
bytecode length exceeds limits. This approach is impractical in my
application, as the transformation involves quite a few steps. It would be
too expensive to generate the bytecode from the Jimple instructions after
each step.

2. Use a worse case estimate. Lets say we know a Jimple instruction can
never generate more than N number of bytes of bytecode, then we can estimate
the length of the bytecodes by using the multiplication factor. (What value
is N?)

What do you think? Has anyone come across this problem before and what is
your solution?

Thanks,
Stephen