systems · sub-star

neon_vm

stack-based virtual machine executing packed bytecode.

readme

A lightweight virtual machine in native C that executes densely packed binary opcodes through a stack-based pipeline, emulating the architecture behind runtimes like the JVM and LuaJIT. Written to understand instruction dispatch and how a compiler target actually consumes bytecode.

signal log

• stack-based execution loop that decodes instructions and manipulates a virtual stack.
• bytecode chunking: data structures for storing and decoding densely packed opcodes and their constants.
• written in native C to keep dispatch overhead minimal.
• bytecode is treated as untrusted input: every step checks stack overflow and underflow, constant indices, truncated operands, and running off the end without a return.
• single-step dispatch (vmStep) drives both the CLI and a browser debugger that shows the instruction pointer, stack and constant pool after each instruction.
• scoped deliberately small: six opcodes, one value type, no control flow and no compiler in front of it. bytecode is hand-assembled to isolate the dispatch loop itself.

built with