This is a modified version of the cairo compiler, with specific symbolic language support.

Installing

Clone this repo, and cd to repo root, then use the following command to install it:

pip install .

Adding verify statements

Usage

Use verify a op b to add a verify statement, for example:

func main():
  [ap] = 1000; ap++
  verify [ap-1] != 0
  ret
end

Example testing commands:

cairo-compile ./tests/test2.cairo --output ./tests/test2_compiled.json
cairo-run --program=./tests/test2_compiled.json --print_output --print_info --relocate_prints --print_memory

Creating A Symbolic Variable

Note

Currently this won't create an actual symbolic variable. Instead, it returns a special (and concrete) value 6626069934 as a placeholder.

Usage

Use symbolic(type, tag) to create a symbolic variable, for example:

func main():
    [ap] = 'sym0'; ap++
    [ap] = symbolic(felt, 'sym0'); ap++
    ret
end

which compiles to the following bytecodes:

...
"data": [
  "0x480680017fff8000",
  "0x73796d30",
  "0x486680017fff8000",
  "0x73796d30",
  "0x208b7fff7fff7ffe"
],
...

Example testing commands:

cairo-compile ./tests/test1.cairo --output ./tests/test1_compiled.json
cairo-run --program=./tests/test1_compiled.json --print_output --print_info --relocate_prints --print_memory

Instruction Decoding

This version adds a new field SYMBOLIC to Instruction.Res, which now looks like the following:

class Res(Enum):
    # res = operand_1.
    OP1 = 0
    # res = operand_0 + operand_1.
    ADD = auto()
    # res = operand_0 * operand_1.
    MUL = auto()
    # res is not constrained.
    UNCONSTRAINED = auto()
    # res is symbolic
    SYMBOLIC = auto()

You can use the following command to test the instruction decoding:

from starkware.cairo.lang.compiler.encode import decode_instruction

# this decodes the line: [ap] = 'sym0'; ap++
# where 0x480680017fff8000 is 5189976364521848832
# and 0x73796d30 is 1937337648
decode_instruction(5189976364521848832,1937337648)
# expected return:
# Instruction(off0=0, off1=-1, off2=1, imm=1937337648, dst_register=<Register.AP: 0>, op0_register=<Register.FP: 1>, op1_addr=<Op1Addr.IMM: 0>, res=<Res.UNCONSTRAINED: 3>, pc_update=<PcUpdate.REGULAR: 0>, ap_update=<ApUpdate.ADD1: 2>, fp_update=<FpUpdate.REGULAR: 0>, opcode=<Opcode.ASSERT_EQ: 1>)

# this decodes the line: [ap] = symbolic(felt, 'sym0'); ap++
# where 0x486680017fff8000 is 5216997962286071808
# and 0x73796d30 is 1937337648
decode_instruction(5216997962286071808,1937337648)
# expected return:
# Instruction(off0=0, off1=-1, off2=1, imm=1937337648, dst_register=<Register.AP: 0>, op0_register=<Register.FP: 1>, op1_addr=<Op1Addr.IMM: 0>, res=<Res.SYMBOLIC: 4>, pc_update=<PcUpdate.REGULAR: 0>, ap_update=<ApUpdate.ADD1: 2>, fp_update=<FpUpdate.REGULAR: 0>, opcode=<Opcode.ASSERT_EQ: 1>)

You can see the two instructions are decoded to the same instruction, except for the res field: the second one has a special SYMBOLIC value set.

Notes

• Currently only the compiler is modified. The interpreter and other infrastructure remains still, which means they cannot handle the extra SYMBOLIC value.
• The imm value can be recovered to short text, i.e., 1937337648 can be recovered to sym0. You'll need to read cairo source code to do that if you want the original text.
• Currently the type (e.g., felt) is not encoded into the instruction. So you can treat every symbolic creation as symbolic integer or symbolic bitvector (depending on the backend type used by the symbolic execution engine).

---

Introduction

Cairo is a programming language for writing provable programs.

Documentation

The Cairo documentation consists of two parts: "Hello Cairo" and "How Cairo Works?". Both parts can be found in https://cairo-lang.org/docs/.

We recommend starting from Setting up the environment.

Installation instructions

You should be able to download the python package zip file directly from github and install it using pip. See Setting up the environment.

However, if you want to build it yourself, you can build it from the git repository. It is recommended to run the build inside a docker (as explained below), since it guarantees that all the dependencies are installed. Alternatively, you can try following the commands in the docker file.

Building using the dockerfile

Note: This section is relevant only if you wish to build the Cairo python-package yourself, rather than downloading it.

The root directory holds a dedicated Dockerfile, which automatically builds the package and runs the unit tests on a simulated Ubuntu 18.04 environment. You should have docker installed (see https://docs.docker.com/get-docker/).

Clone the repository and initialize the git submodules using:

> git clone [email protected]:starkware-libs/cairo-lang.git
> cd cairo-lang

Build the docker image:

> docker build --tag cairo .

If everything works, you should see

Successfully tagged cairo:latest

Once the docker image is built, you can fetch the python package zip file using:

> container_id=$(docker create cairo)
> docker cp ${container_id}:/app/cairo-lang-0.9.0.zip .
> docker rm -v ${container_id}