README.md

Function

Good day to learn about the Function methods, isn't it? Function is the second of our fundamental trio. It can be used to:

• Check the corresponding function's properties
• Get different types of instructions belonging to this function
• Work with arguments
• ...

Don't forget about the Callable object, Function inherit its methods!

Methods

From the most important methods, I can highlight the following:

• The group of property methods (.is_internal(), .is_public(), .is_payable(), etc.)
• The group of Instructions getters (.if_instructions(), .asm_instructions(), etc.)
• .signature(), .hashed_signature(), and .name()
• .get_contract() to step up to the contract
• .arguments() to get the Arguments object
• .modifiers() to get the Modifiers object
• .dump_into_json(), I'll make an additional article about it

There are about 50 methods in total, so make sure to check them all in the documentation 1 and 2.

Example

I'll share one of my unfinished glides as an example where I use Function to check the arguments:

from glider import *


def query():
    instructions = (
        Functions()
        .with_one_property([MethodProp.EXTERNAL, MethodProp.PUBLIC])
        .with_all_properties([MethodProp.HAS_CALLEES])
        .with_arg_type("address")
        .without_modifier_name(["onlyOwner", "onlyRole", "onlyAdmin"])
        .instructions()
        .external_calls()
        .with_callee_function_name("transferFrom")
        .exec(100)
    )

    result = []
    for instruction in instructions:
        function = instruction.get_parent()
        addr_from = check_transfer_argument(instruction, function)

        if not addr_from:
            continue
        if not check_requirements(instruction, function, addr_from):
            continue

        result.append(instruction)

    return result


def check_transfer_argument(instruction, function):
    function_addr_args = function.arguments().with_type("address")
    calls = instruction.get_callee_values()

    for call in calls:
        if call.signature == "transferFrom(address,address,uint256)":
            addr_from = call.get_args()[0]

            for function_addr_arg in function_addr_args:
                if addr_from.expression == function_addr_arg.name:
                    return function_addr_arg.name


def check_requirements(instruction, function, addr_from):
    return True

As you can see, I use function = instruction.get_parent() to step up from the instructions that contain transferFrom() call to their corresponding functions.

Then, in the check_transfer_argument() Python function, I query the function's arguments using function.arguments().with_type("address") and try to match between them and transferFrom() arguments to check whether the call uses arbitrary from value.

The glide is unfinished because of the empty check_requirements() in the end. There should be some algorithm to check whether the from variable is used in a require or if.

You can try to modify it and finish the function, I don't mind, just show me what it looks like afterward :)

Read next: Instruction