Questions tagged [function]
The function tag has no usage guidance.
115
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4
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Unexpected overflow result from a function when inputting max uint256
I am looking at the following function tickUpper that is supposed to retrieve the 24 bits of a 256 bit number beginning at bit 208. It's cast to an int24 because it interfaces with uniswap ticks.
I ...
- 41
0
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0
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7
views
Why are these functions using %128?
I am looking at the following functions which (i) take a 7-bit number (up to 127) and add it to 256-bit number, starting 64 positions in from the right and (ii) read that 7-bit number given the 256-...
- 41
1
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0
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10
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How is this legal? _merkleProof.verifyCalldata(root, leaf)
Code: https://www.contractreader.io/contract/mainnet/0x0C7D4bdA40CF78F9F1BAf6e3D5774f1E22c9CC4B
My question is about this verifyCalldata() call:
function verifyAddress(
uint256 _projectId,
...
- 111
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0
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21
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how to get a function's signature that have a structre as parametter
function createClone(
uint256 dbId,
launchpadLib.IDOInfo memory _idoInfo,
launchpadLib.IDOInfoTwo memory _IDOInfoTwo
) external{}
I have this funtion how can i make signature of this function with ...
1
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0
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9
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Attack vector in direct transfer function in EC721
How the attack vector would look like in case of direct transfer function in EC721 standard. It is described in the comment
A marketplace is transferring an NFT from Bob to Mary (among many
other &...
2
votes
2
answers
110
views
What is an Internal function type variable?
I was going through solidity documentation and found this paragraph inside "Function Types" section https://docs.soliditylang.org/en/v0.8.21/types.html#user-defined-value-types
A function of ...
- 25
2
votes
1
answer
53
views
Possible way to hack Solidity into executing a function directly from a struct as a method? (v0.8.20)
pragma solidity 0.8.20;
contract SolidityLimitTest {
mapping (address => Hack) private Hackable;
struct Hack {
uint amount;
function(uint) returns (uint) ten_x;
}
...
- 79
0
votes
1
answer
41
views
What is the correlation between "Hash" (Method ID) & "Name"
I was checking Etherscan and come across a deployed contract (Create contract), but the method id was 0x60a06040.
I then used https://openchain.xyz/signatures?query=0x60a06040 and found out that the ...
- 25
0
votes
1
answer
10
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Do you have to explicitly state in the body of a function that it should return something?
I'm looking at the following function which is supposed to return (uint8 id, uint8 nextId). I see that in the body of the function, the return statement is within an "else" statement - see ...
0
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1
answer
13
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Creating a local variable in an if statement?
I'm looking at a function that creates a local variable in an if statement. If someone called that function and the condition to the if statement was not triggered, that local variable wouldn't exist, ...
2
votes
1
answer
74
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Where in the code of this unstake function is ETH actually transferred?
I am looking at this repo, which is contracts for a decentralized pegged asset issuance system backed by liquid staking tokens like rETH. Specifically, I have a question about the functions unstake in ...
0
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1
answer
18
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Can you refer to a contract inside itself?
Sorry this is a very minor question but the following is part of a contract called LibOrders.sol. The function below calls LibOrders.cancelOrder....normally I think you would just put "...
1
vote
1
answer
57
views
Two people calling this function at exactly the same time
I was looking at Rocket Pool's docs on interacting with other contracts and they included a simple example function that another protocol could use to accept deposits of ETH, forward it to RP, and get ...
1
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1
answer
16
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Can you return something only some of the time with a function in solidity?
I am looking at a function that says it returns two uints, but the return statement is inside an else statement, so obviously there are conditions under which nothing would be returned. Can you have ...
1
vote
1
answer
25
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How can I execute a call from a contract using another contract?
I own a contract (contract A), which in turn, when deployed, created a secondary contract (Contract B).
I have funds trapped in contract B, contract B, has a function that allows its owner to withdraw ...
0
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1
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16
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Revert inside a for loop
If there is a revert inside a for loop that is inside a function, and the revert is triggered, will the whole function revert?
2
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1
answer
29
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Invoking a function with different amount of input than the function takes
function sub(uint256 a, uint256 b) internal pure returns (uint256) {
return sub(a, b, "SafeMath: subtraction overflow");
}
function sub(
uint256 a,
uint256 b,...
1
vote
1
answer
18
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When calling a custom function on an ERC721 it keeps reverting when called from the frontEnd but works if called from remix
I am having an issue calling a function on one of my contracts.
I have an ERC721 contract that has a function getTokenUnlockableContent.
function getTokenUnlockableContent(
uint256 tokenId
) ...
- 11
0
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1
answer
230
views
How Can I Filter Ethereum Transactions by Method ID or Name, Similar to Etherscan's Advanced Filter Feature
I am working on a project where I need to retrieve all transactions associated with a specific method within a given block or set of blocks. As an example, Etherscan provides this functionality ...
1
vote
2
answers
49
views
how does swapExactTokensForETHSupportingFeeOnTransferTokens work and its inputs
I tried many things on inputs but unfortunately I am just receving a gas error (the one that says would likely fail if continued)
How does the function input works exactly?
uniswapV2Router....
- 11
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0
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114
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TypeError: AbiCoder is not a constructor, testing purchaseSnack function is failing. I think due to not handling ether conversion correctly
I am trying to write a test script using hardhat to test the purchaseSnack function but I keep receiving these errors.
1) VendingMachine
Should fail if insufficient funds are sent:
...
- 1
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1
answer
52
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How can I modify this function to return my wallet address?
How do I modify this function to return my wallet address using uint160? I want to remove all the for-loop logic. I've created this contract and sent ETH to it, but I am having trouble getting the ETH ...
0
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1
answer
12
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Function with both override and virtual keywords
What I understood from this is that if a function has virtual keyword, it can be overridden. And if a function has the keyword override means it is overriding another function. So, does the function ...
- 83
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1
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14
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Hello. Is token mint allowed in this snippet? Or can it be mint again?
function mint(address user, uint256 value) external onlyOwner {
require(user == OWNER, "NOT_OWNER");
balances[user] = balances[user].add(value);
totalSupply = totalSupply.add(value);
...
0
votes
2
answers
103
views
Calling Aave Lending Pool V2 "Borrow" function returns "reverted with reason string 59"
My smart contract is trying to use stETH as collateral to borrow 250 WETH on the Aave Lending Pool V2, but the borrow function reverts with code 59:
BORROW_ALLOWANCE_NOT_ENOUGH = '59'; // User borrows ...
0
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1
answer
35
views
Call contract's function
I'm new in solidity and blockchain itself.
Typed myself contract for Voting in VSCode and tried to figure out how I can run code and research workflow and etc. During researching figured out that for ...
- 3
0
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1
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23
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How to use another deployed smart contract functions?
What I want to do is deploy a smart contract with functions that other deployed smart contracts can call and get a response from.
How do I implement this? Is there any useful guides you guys know I ...
0
votes
1
answer
69
views
Chainlink Functions return an array or list of strings from Functions-request-source.js
Hope someone can help.
I am stuck trying to work out how best to extract the different string values from the returned bytes data.
Chainlink Function request source requires the return value to be a ...
- 15
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2
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31
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How do you use `delete` on a function?
"If a function type variable is not initialised, calling it results in a failed assertion. The same happens if you call a function after using delete on it." is a quote from
the official ...
- 279
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20
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does empty function has security risks?
I have to implement the following interface in my contract
interface IMetadataRenderer {
function tokenURI(uint256) external view returns (string memory);
function contractURI() external view ...
0
votes
1
answer
24
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ParserError in solidity
I wrote the following contract (for educational purposes):
// SPDX-License-Identifier: MIT
pragma solidity 0.8.8;
contract Coin{
holders[] public investors;
mapping(address=>...
- 105
1
vote
1
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42
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How I do I calculate the price of a Token as the amount of the token bought increases
Let say I created a Min price = 0.00056 ether for 150 coins which is the Min amount and the Max price = 0.1 for 20,000 coins which is the Max amount. What will be the price of the coin when I buy 1000 ...
- 43
2
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1
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21
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SOLIDITY NOOB QUESTION. Is it necessary to specify that a function is a view function if it's obviously a view function?
For example:
function contains(address _key) public view returns (bool) {
return map[_key] != 0;
}
I don't know how this could be manipulated to change the state of anything, so to me it ...
- 67
8
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3
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265
views
The redundant `_from` parameter in the `transferFrom` function of an ERC721
The Non-Fungible Token Standard (described in EIP-721) specifies, among other things, the signature of the transferFrom() function: function transferFrom(address _from, address _to, uint256 _tokenId) ...
- 279
1
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1
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27
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Is there a decentralized version of Cloudflare Workers?
Is there a decentralized version of Cloudflare Workers or some comparable service like AWS Lambda functions or GCP Cloud Functions? I would love a blockchain based, or just a decentralized version of ...
- 361
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10
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Fuction type assined as as variable to another func name
So, here is a code snippet:
function stake (
AssetType _assetType,
uint256 _timelockId,
uint256,
uint256,
uint256
) external nonReentrant {
...
1
vote
1
answer
45
views
What is Solidity's equivalent of raw_call()?
I'm wondering, does Solidity also have a raw_call() function like Vyper which sends a byte[] array (payload) as calldata to a specific address?
If so, what is that function? Is it also raw_call()?
- 35
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1
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71
views
Function isn't returning the uint256 value after initializing mapping
I'm facing a problem with the function return type in solidity. Here is my code:
// SPDX-License-Identifier: MIT
pragma solidity ^0.8.17;
contract Birth {
mapping(uint256 => bool) public ...
0
votes
1
answer
60
views
Modifier vs function call
What is more gas efficient and secure, using a modifier(for example only owner) or calling a function to verify state(calling a function that returns owner address and compares that to the address ...
- 31
0
votes
1
answer
107
views
Error When Passing Struct as Input to Function in Solidity
I'm trying to just call a function that has a struct argument...The thing is that Remix somehow doesn't recognize all the inputs from the struct in the function.
I tried making the image very ...
- 23
0
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1
answer
14
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Function override error and abstract error after importing the contract
*this a contract for erc721:
contract erc721{
event Transfer(address indexed _from, address indexed _to, uint256 indexed _tokenId);
event Approval(address indexed _owner,address indexed _approved, ...
- 29
1
vote
1
answer
19
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Declaration error: undeclared identifier error in remix while using exiting Owner contract's function getOwner. Kindly help in solving
function withdraw() external isOwner() {
address payable owner = address(uint160(getOwner()));//**this is the line I get err
owner.transfer(address(this).balance);
}
owner contract:
function ...
- 29
4
votes
1
answer
34
views
Is it possible to use interface functions as types?
I would like to use a function defined in an interface as a function type, like this:
pragma solidity >=0.8.17;
interface Foo {
function myFunction() external;
}
contract Contract {
...
- 17.3k
1
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1
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69
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Getting two different booleans calling a function 2 times in a row
I tried to create a function which could return me 2 different booleans after I call it two times in a row. I tried my best to use different random methods like storing block.timestamp in an uint, or ...
- 21
1
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0
answers
36
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How to identify where coin/token value is changed
I'd like to build an algorithm that analyzes value creation, transfer and destruction on a blockchain (such as new ETH minted, ETH gas burned, ERC-20 tokens transferred, etc.).
Assuming I have a ...
- 13
1
vote
1
answer
104
views
Does it make any sense to specify reference type function input parameters as calldata if the given function is only called contract to contract?
As far as I am aware contract to contract calls store input arguments in memory. Or put more precisely they store them in memory and they can be accessed with CALLDATALOAD within the the new call ...
- 181
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18
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What are the advantages/disatvantages to specify a struct param in a function as calldata vs. memory?
If I am not modifying the input parameter in the function body are there any reasons a reference type parameter should be labeled as stored in memory?
More generally what are the reasons to go for ...
- 181
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37
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Do i need to fund my contracts with eth
I have a protocol composed of multiple contracts which interact with each other, when a user call a transaction in one of the contracts, the contract calls other contracts functions .
The question is :...
- 328
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1
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62
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contract recursive dependency
i have two contracts the first one has a function which must be called only by the second contract :
contract A {
address contractBAddress;
uint256 number;
modifier onlyB() {
...
- 328
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1
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70
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Why isn't calldata used in this function's argument? (OpenZeppelin/OwnableUpgradeable.sol)
Solidity noob here; reading about data locations i've learned that whenever you don't need to store or modify a function's input value it's actually more gas efficient to set its location to calldata (...
