Why

Currently, the VM logic optimistically fills the memory to fit the res logic and opcode. There is however no check that the operation is legit. For example, an assert 0 = 1 would just lead to a memory written to 0, then overridden to 1.

What

Raise in step when the operation is not possible

How

See https://github.com/starkware-libs/cairo-lang/blob/efa9648f57568aad8f8a13fbf027d2de7c63c2c0/src/starkware/cairo/lang/vm/vm_core.py#L386

Why

The project currently uses vanilla js. It would be better (easier to maintain, to understand) to use typescript.

What

Rewrite all the codebase in typescript

How

1. Follow the doc to use ts in google app scripts
2. Create a types.ts file gathering all the types
3. Refactor codebase to use ts

Why

In the current PoC, there is only a step method that generate the next step of the VM. We need a method to make the whole run directly as well

What

Create a run method, and a Run menu item, to end the run

How

See the while loop of the python vm
https://github.com/starkware-libs/cairo-lang/blob/efa9648f57568aad8f8a13fbf027d2de7c63c2c0/src/starkware/cairo/lang/vm/cairo_runner.py#L343

Logic is the same, where the final_pc has been put in the Execution column in the initialize step (see #3).

The function should at any stage of the run, ie. from the beginning (right after initialization) or after few steps have already been executed.

Why

The cairo VM runs cairo wasm, and cairo0 is very close to it.

What

• Create a python-poetry project
• add cairo-lang package
• create a simple hello_world.cairo

How

• check https://python-poetry.org/
• poetry init
• poetry add cairo-lang

Create a fibonacci.cairo, fill with a simple function like this one https://github.com/ClementWalter/hello-starknet/blob/main/src/jump.cairo, build and commit

Why

The Cairo VM uses memory segments to track values. In short and almost true, a memory segment is just a list of values, ie. here a list of felt (felt is the only native type of cairo, think of felt as uint252).

A run of the VM actually consists in filling values in memory segments; allocating a segment just means creating an empty list at index i in the segments manager of the VM, much like

{
    0: [],
    1: [],
    42: [],
}

could be a memory with 3 initialized segments (with indexes 0, 1 and 42).

Segments can be allocated during the run (when the dev uses the alloc() function) or by the VM itself at the beginning of a run for given builtins. In cairo0, these builtins are declared at the tile level using the % builtin directive, and at the function level using corresponding implicit arguments.

The list of builtins actually available is:

[
  "output",
  "pedersen",
  "range_check",
  "ecdsa",
  "bitwise",
  "ec_op",
  "keccak",
  "poseidon",
]

Each builtin requires its own memory segment as these builtins actually enforces some rules over the segment. For example, the range_check segment will enforce that every values contained in this segment are actually no greater than 2**128.

Consequently, when initializing the VM for running a program, one needs to create as much memory segments as required.

What

The Cairo VM gs uses native sheet columns as memory segments.
The function should add the corresponding column with their header as names next to the Execution column

How

Follow the python VM https://github.com/starkware-libs/cairo-lang/blob/efa9648f57568aad8f8a13fbf027d2de7c63c2c0/src/starkware/cairo/lang/vm/cairo_runner.py#L216
Note that program_base is always the first segment, and Execution the second.

Add a menu in the UI to actually trigger the call

The CairoVM will for now only run the main entrypoint, so the final fp and pc segments should be added last, and their reference be added in the execution segment.

Why

Currently, the PoC showcase a small fibonacci program copy/pasted. We need to be able to load any compiled artifact instead.

What

Add a menu in the UI to load a program. This should open a file picker to upload a json file. Once uploaded and validated, the sheet should be updated as follows:

• the Program tab is updated with the loaded program bytecode in column A
• column B is filled with DECODE_INSTRUCTION(A) as as required
• the Run tab is cleared with the loaded program bytecode in program, and the segments initialized

How

For the file picker, check the google doc
For the segment initialization, see #3

Why

The fibonacci example is a very simple function not using any builtins. We want to add simple function with builtins as well.

What

Copy the file from https://github.com/ClementWalter/hello-starknet/blob/main/src/dict.cairo next to fibonacci, compile and commit result.