Krakatau VS peda

Since Java bytecode uses MUTF-8, which encodes astral characters as surrogate pairs, I've had to implement this conversion in Python multiple times, in Krakatau and Enjarify.

Not sure how applicable this is for your project since my compiler was written in Python, but I used Krakatau.

Here is one that disassembles the bytecodes and reassembles them https://github.com/Storyyeller/Krakatau .

There's an additional problem that unlike regular assembly or LLVM assembly where there's some fully supported standard format, Jasmin is a third party program and different JVM assemblers and disassemblers disagree on so many things. There are also some newer assemblers and disassemblers like Krakatau you could try instead. Krakatau has different syntax than Jasmin or javap.

Krakatau - Java decompiler and disassembler.

The compiler outputs bytecode in a text format, which can be assembled into .class files using the Krakatau assembler. Figuring out how to translate features like nested functions and nonlocals to JVM was pretty interesting, and having access to Java’s standard library made the whole thing much easier than expected.

Looks like they are using PEDA.

There are a lot of these types of tools already in the reverse engineering community (in order of lowest chance of breaking when you throw really weird stuff at it):

GEF: https://gef.readthedocs.io/en/master/

PWNDBG: https://github.com/pwndbg/pwndbg

PEDA: https://github.com/longld/peda

They also come with a slew of different features to aid in RE/exploit dev, but many of them are also useful for debugging really weird issues.

PEDA - GDB plugin (only python2.7).

peda - Python Exploit Development Assistance for GDB.

Did you follow the instructions? Step 2 adds PEDA to your ~/.gdbinit so it will/should load every time you open gdb. So if it doesn't work check your ~/.gdbinit file.