You can find the contract address by using the library function `get_contract_address()` . For example:


`from starkware.starknet.common.syscalls import (get_contract_address,)`


`# ...`


`let (contract_address) = get_contract_address()`


ㅤ
_This answer was originally posted on [Triality](https://triality.org/question/575)_

How can I find the current contract's address in Cairo? Is there an equivalent to `address(this)` from Solidity?


ㅤ
_This question was originally posted on [Triality](https://triality.org/question/575)_

Cairo: How do I find the current contract's address?

I can't find info on what `vm_enter_scope` does within hints in the cairo-lang repo. Heres an example:
https://github.com/starkware-libs/cairo-lang/blob/d61255f32a7011e9014e1204471103c719cfd5cb/src/starkware/cairo/common/patricia.cairo#L117

Can anyone summarize?

_This question was originally posted on [StarkNet Discord](https://www.newton.so/view?tags=discord)_

I can't find info on what `vm_enter_scope` does within hints in the cairo-lang repo

test another new question new

Howdy.


I am trying to dev against the starknet devnet to build my frontend and am experiencing some issues. With argent, it seems that the version in the chromestore isn't up to date with the devnet's fee token, so I can create an account and fund it, but still not be able to do any transactions.


When I try to build from source, I get an error about something involving a react server or something.


Trying braavos, I am able to transact against dev net (invoke method calls) but calling views seems to be going against a wrongly set provider. So when I connect with the wallet, all my calls get an error that 'the contract isn't deployed' because it is checking against a goerli-testnet provider rather than my devnet. I can set a default provider manually, but it gets overwritten when I access the wallet.


I am hoping that there is maybe a third wallet or something that can help me sidestep the concern. But perhaps my understanding of the situation is misguided. I am using starknet-react, if that maybe is contributing to the issue.


﻿  



ㅤ
_This question was originally posted on [Triality](https://triality.org/question/926)_

How do I develop against cairo devnet with browser wallets?

Everyone knows that secure code is essential. Can someone explain what is reentrancy?
I am curious about the reentrancy attack in StarkNet – is it a problem in Cairo Language and how to protect my smart contract from this attack?

How to protect my contract from reentrancy in Cairo Language / StarkNet?

I transferred USDC from Starknet to L1 via Starkgate.
In Starknet Explorer, it shows the assets received on L1, but I have no USDC received on L1. It’s been more than 12 hours. What could be the problem?!

_This question was originally posted on [StarkNet Discord](https://www.newton.so/view?tags=discord)_

Problem with transfering USDC via Starkgate. Can anyone help?

In the following function I am presented with the following error, even though my code does not make it to this function. What am I doing wrong?


`func fill_in_row{output_ptr: felt*}(row_idx : felt, row_size : felt, curr_row : felt*) {` 


 `if (row_idx == row_size-2) {`


 `return ();`


 `}`


 `let val : felt = curr_row[row_idx-1] + curr_row[row_idx];`


 `serialize_word(val);`


 `curr_row[row_idx+1] = val;`


 `return fill_in_row(row_idx+1, row_size, curr_row);`


`}`


Error: code:80:5: While expanding the reference 'curr_row' in:


 curr_row[row_idx+1] = val;


 ^******^


code:72:73: Expected a register. Found: [fp + (-4)].


ㅤ
_This question was originally posted on [Triality](https://triality.org/question/1156)_

Cairo Error: Getting Error while setting value of item in array

Hello! This is day 13 of the 17 days of the Cairo Challenge. And I have no idea how to solve the [playground](https://www.cairo-lang.org/playground/) exercise “Pedersen Hash”.  Perhaps you can help me?

```
// The following code implements a Pedersen hash chain.
// Given the [Pedersen hash](https://docs.starkware.co/starkex-docs/crypto/pedersen-hash-function) function `H`, which
// takes two field elements and returns one representing their hash,
// a hash chain on inputs x_0, x_1, ..., x_n is the result of
// H(H(...H(H(x_0, x_1), x_2), ...,x_{n-1}), x_n)
// For example, the hash chain of (1, 2, 3, 4) is H(H(H(1, 2), 3), 4).
//
// Fix the function `hash_chain` to correctly implement the
// hash chain. Run your code to test it.
//
// Note: Don't use starkware.cairo.common.hash_chain (it computes the chain differently).

// Use the Pedersen builtin.
%builtins pedersen

from starkware.cairo.common.alloc import alloc
from starkware.cairo.common.cairo_builtins import HashBuiltin
from starkware.cairo.common.hash import hash2

// Computes the Pedersen hash chain on an array of size `length` starting from `data_ptr`.
func hash_chain{hash_ptr: HashBuiltin*}(data_ptr: felt*, length: felt) -> (result: felt) {
    if (length == 2) {
        let (result) = hash2(x=[data_ptr], y=[data_ptr + 1]);
        return (result=result);
    } else {
        // Fix here:
        return (result=123456);
    }
}

func main{pedersen_ptr: HashBuiltin*}() {
    alloc_locals;
    // Allocate a new array.
    let (local data_ptr: felt*) = alloc();
    // Fill the new array with field elements.
    assert [data_ptr] = 314;
    assert [data_ptr + 1] = 159;
    // Run the hash chain.
    let (result) = hash_chain{hash_ptr=pedersen_ptr}(data_ptr=data_ptr, length=2);
    // Check the result.
    assert result = 307958720726328212653290369969069617958360335228383070119367204176047090109;

    // Fill two more cells in the array.
    assert [data_ptr + 2] = 265;
    assert [data_ptr + 3] = 358;
    // Compute the hash chain on all four cells.
    let (result) = hash_chain{hash_ptr=pedersen_ptr}(data_ptr=data_ptr, length=4);
    assert result = 1828757374677754028678056220799392919487521050857166686061558043629802016816;
    return ();
}
```

---

> Answers to this question are a part of the ✨ 17 days of Cairo Lang with Playground & Newton. ✨
> 

*Vote for your favorite answer - the best answer will win a $10 award. A new day – a new reward! During the next 17 days, our goal is to attract more developers to the Cairo language and to systematize the knowledge of Cairo lang. [Read rules](https://www.notion.so/17-days-of-Cairo-Lang-with-Newton-550dfcda6a2d449ca468be293c776578)*

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Cairo: How do I find the current contract's address?

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