they are safe if used correctly.

this means specifically that every time there is a `Uint256` input to a function (especially if that is not a privileged function and any user can call it), you **must** call `uint256_check()` on it first. if you do that, you'll be safe and you don't have to worry about `Uint256`'s security issues.

to understand specifically why that is and how the `Uint256` functions work, you can refer to an article we wrote on the topic:
https://twitter.com/ggballas/status/1591119157034090513

if you're looking to go to mainnet with your dapp, you're welcome to consult with us for free about any security issues. we specialize in starknet:
https://gingersec.xyz/

ggballas

Hey, I'm curious if uint256 variables are safe to use? They are using 2x128 bits, while a native felt uses only 252 bits. 

Can anyone explain?

vargastartup

Is uint256 math operators like uint256_le safe? Why do I need to use uint256_check?

What is the extension that shows you errors before compilation ser?

Which is this extension that shows you errors before compilation ser?

Hello, I am facing an issue with `starknet-devnet (v0.3.1)` . I do not manage to run RPC `starknet_addInvokeTransaction` with positional parameters; yet it works with pathfinder and other vers like `starknet_estimateFee`. It returns `int() can't convert non-string with explicit base`. It is working fine on GOERLI. I have document the case on the repo https://github.com/Shard-Labs/starknet-devnet/issues/282. Does anyone have an example of a positional request to `starknet_addInvokeTransaction` on devnet that is working? The test inside the testsuite is also using named parameters. Thank you for your help

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

Does anyone have an example of a positional request to `starknet_addInvokeTransaction` on devnet that is working?

I'm new to Cairo and I want to know what is the difference when I write `let x = 1;` and `tempvar x = 1;`. Is there any difference in Cairo Lang between let and tempvar?

Cairo: let vs tempvar what is the difference?

Hi,

any idea what this could be caused by? This function is mentioned only once in the whole codebase. I’m trying to do protostar build

```python
Redefinition of '__wrappers__.get_pool_balance.__wrapped_func'.

func get_pool_balance{syscall_ptr : felt*, pedersen_ptr : HashBuiltin*, range_check_ptr}(
```

This error always appears with the first function it encounters that is annotated with either @view or @external

Can be reproduced in the repro-redefinition branch of [https://github.com/CarmineOptions/carmine-protocol.git](https://github.com/CarmineOptions/carmine-protocol.git)

Has anyone seen this error in proto? Redefinition of *`wrappers.*ourfunctionname.__wrapped_func__’`?

Any idea what this could be caused by?

How do I connect my DAPP to Starknet mainnet using starknetjs?

hi, i used the starkgate bridge from stark to eth one hour ago. Withdrawal has not occurred yet. How many hours does the process take? My tx hash is: <address>cfa0c02d013658804505506

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

How long does starkgate bridge process?

Hey! The title sort of summarizes the question. I was wondering if there's any project where I can see an example of how something like `keccak256(abi.encodePacked(var1, var2, var3))`  could be achieved in starknet.

If there were a way to concatenate bytes, I think it wouldn't be too complicated, but such a string would never fit in a felt, and using a struct won't result in the same output.

So yes, my question is if there's an equivalent way to achieve this behavior in cairo.

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