THIS PROJECT IS UNSTABLE AND DEPRECATED

I have since started slow work on a more stable, better thought-out project called RabbitVM. It doesn't quite have the same level of documentation but it should work much better.

CarpVM

This is a project I've been slowly working on for about half a year now. The goal is to try and build a small (and decently reliable) VM from the ground up, learning more and more C as I go.

Right now there are instructions, registers, a stack, data memory, and calls. Not sure if recursion works... it should in theory. Haven't tested.

CONSIDER THIS PRE-ALPHA SOFTWARE. Things change more than they do in Rust!

   

Installation

Getting Carp

If you already have a local copy (cloned before submodule was added)

• git fetch
• git rebase
• git submodule init
• git submodule update

If you don't already have a local copy

• git clone --recursive

NOTE: If git submodule status doesn't return a SHA1 hash and repository name, you have a problem. NOTE: Recursive clone is for testing library. If not included, tests will not build.

Building Carp

1. make
2. make test (optional)
3. make install
4. make clean (optional)

Tested Machines

Arch (bit) | OS (with version, name) | Compiler (with version) ---------- | ----------------------- | ----------------------- 64-bit | Ubuntu 12.04 (precise) | gcc 4.6.3 64-bit | Ubuntu 14.04 (trusty) | gcc 4.8.2 32-bit | Ubuntu 14.04 (trusty) | gcc 4.8.2 64-bit | OS X 10.9.4 (Mavericks) | clang 3.2 32-bit | OS X 10.9.4 (Mavericks) | gcc 4.2.1 64-bit | Arch Linux 3.13.6-1 | clang 3.4.2 64-bit? | Arch Linux 3.13.6-1 | gcc 4.9.0 20140604

Use

NOTE: See carp -h for help with command-line options.

Interpreter

1. Write a Carp file - see SYNTAX.md. More formal spec coming.
2. Run ./carp.out -f your_file.carp.

API

1. Include carp/carp_machine.h in your program.
2. Run gcc program.c /usr/local/lib/libcarp.a -o program.out.

Instruction set

Opcode | Arguments | Description ------ | --------- | ----------- HALT | exit code | Sets ext to given code, halts, and attempts to clean up stack, data memory, and label memory. NOP | | Does nothing. Seriously. LOADR | reg, val | Loads given integer value into given register. LOAD | diff | Loads value at location fp + diff in the stack. STORE | diff, val | Stores value at location fp + diff. MOV | dst, src | Copies contents of src register into dst register. ADD | | Pops the top two integers from the stack and pushes their sum. SUB | | Pops the top two integers from the stack and pushes the difference (lower minus upper). MUL | | Pops the top two integers from the stack and pushes their product. MOD | | Pops the top two integers from the stack and pushes lower % upper. SHR | | Pops the top two integers from the stack and pushes lower >> upper. SHL | | Pops the top two integers from the stack and pushes lower << upper. NOT | | Pops top integer from stack and pushes bitwise NOT of that integer. XOR | | Pops the top two integers from the stack and pushes bitwise XOR.. OR | | Pops the top two integers from the stack and pushes bitwise OR. AND | | Pops the top two integers from the stack and pushes bitwise AND. INCR | reg | Increments value in given register. DECR | reg | Decrements value in given register. INC | | Increments the value at the top of the stack. DEC | | Decrements the value at the top of the stack. PUSHR | reg | Pushes value in given register. PUSH | val | Pushes given value. POP | reg | Pops an integer from the stack and dumps it into given register. CMP | | Pops the top two integers from the stack and checks if equal. 0 means equal. Pushes result. LT | | Pops the top two integers from the stack and checks if lower < upper. Pushes result. GT | | Pops the top two integers from the stack and checks if lower > upper. Pushes result. JZ | addr | Jumps to given absolute address if top of the stack is 0. RJZ | diff | Adds differential to ip (relative jump) if top of the stack is 0. JNZ | addr | Jumps to given absolute address if top of the stack is not 0. RJNZ | diff | Adds differential to ip (relative jump) if top of the stack is not 0. JMP | addr | Jumps to given absolute address unconditionally. RJMP | diff | Adds differential to ip (relative jump) unconditionally. CALL | key/addr | Save state and set IP to value in data memory at key. Function may return value in ax. RET | | Put top of the stack into ax and load previous state. PREG | reg | Prints contents of given register. PTOP | | Peeks top of stack and prints top value.

Registers

Name | Purpose ---- | ------- r0 ... r9 | General purpose. ax | Return value for user-defined function. bx, cx, dx, rx | ... something in the future. Just taking up space for now. ip | Instruction pointer. Used for keeping place in code, gotos, calling, etc. sp | Stack pointer. fp | Frame pointer. Used to keep state for function calls. gbg | Garbage register mainly used for popping. run | Boolean - is machine running? ext | Exit code.

How to contribute

One way:

1. Check out the TODO.md file to see if anything needs doing.
2. Write some code (following existing implicit style) and submit a pull request.

Another way:

1. Write some code for a feature you want to exist and submit a pull request.

License

GPLv3. See LICENSE.txt.