Questions tagged [solidity]
Solidity is a contract-oriented, high-level language whose syntax is similar to that of JavaScript and it is designed for writing smart contracts in Ethereum to run on the EVM. Solidity is statically typed, supports inheritance, libraries and complex user-defined types among other features.
5,322
questions with no upvoted or accepted answers
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votes
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answer
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Trying to compile example code from pyethapp tutorial
I am trying to follow this example:
https://github.com/ethereum/pyethapp/wiki/The_Console
However, at the point where I should compile the code, I get an error:
In [34]: print c
contract NameReg{
...
- 1,923
8
votes
0
answers
4k
views
SushiSwap - Inner workings?
I've been trying out in the past few days SushiSwap and lately SashimiSwap Contracts & Frontend and while I'm still getting familiar with the code. It turned out to be quite a challenge to make it ...
- 267
7
votes
1
answer
817
views
Natspec Commenting Style for Structs
Is there specific way to explain the variables of a struct using the Natspec format?
I do something like:
struct XYZ{
uint x; //Explain what it does
uint y;
}
Is it this the right way for ...
- 304
7
votes
2
answers
1k
views
Unit testing a Solidity Library function with a struct memory argument
I am trying to unit test a Solidity Library contract function using truffle and web3. My simplified Library contract looks like this:
pragma solidity >=0.5.16;
pragma experimental ABIEncoderV2;
...
- 168
7
votes
1
answer
304
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String Input of three numbers (comma seperated) doesn't work in Remix
So when I try to put in three numbers as a String in a usual setter-method, it doesn't work.
Does anybody know why?
function test(string memory x) public view returns(string memory){
return x;
}...
- 83
7
votes
0
answers
301
views
Can I `eth_call` a non constant function from javascript?
I know that I can't get the return value from a transaction (How to get values returned by non constant transaction functions?), and non-constant functions have return value because they can be called ...
- 30.9k
6
votes
1
answer
165
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Why do these two Ethereum transactions have different gas usages? Can't explain it from the GETH EVM debug traces
Two USDC transfers in the same block, both between non-contract addresses. Both call the same smart contract function transfer() but used very different gas. Some differences I can explain (see below) ...
- 161
6
votes
0
answers
162
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Kademlia: How does Ethereum uses node discovery protocol to avoid sybil/eclipse attacks?
I want to describe a case that's not clear to me. let's say we have 10 peer validator nodes who reach consensus and agree to store some blocks on their chain. Let's say now that a wallet wants to sync ...
6
votes
0
answers
188
views
Need help to understand storage costs
I have tried to implement a simple cellular automaton logic using two different ways to track the final state:
Track every iteration in a multi-dimensional array.
Store only the last two iterations.
...
- 135
6
votes
0
answers
603
views
how to decode/encode ipfs for contracts
It's known that IPFS can use 2 types of CID, v0 and v1. In my contract, I let users store bytes data parameter. They can store some simple text on it or even pass the ipfs hash. This question is about ...
- 1,135
6
votes
0
answers
101
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Deploy gas issue for require reason string
I found a strange case and didn't find out why.
...
modifier onlyMaster() {
require(msg.sender == master || msg.sender == developer, "caller is not the master");
_;
}
...
...
- 126
6
votes
0
answers
1k
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Why does Ethereum use JSON-RPC and not gRPC?
I am fairly new to networking protocols especially JSON-RPC and gRPC as they are not nearly as common in web development as REST. I was reading around and seems like gRPC generally performs better. So ...
- 161
6
votes
0
answers
710
views
solidity-coverage show 0% coverage
I'm trying to make a test coverage for MetaCoin.
This is my package.json, truffle-config.js and
.solcover.js:
module.exports = {
port: 8555,
norpc: true,
compileCommand: '../...
6
votes
4
answers
3k
views
"Mock compiler : Source not found" Error in Remix online IDE
I haven't been able to compile any solidity code because of this error.
How do I solve this problem?
- 61
6
votes
2
answers
2k
views
Web3 Event Filtering timeout
This is the code I use to get all events from a certain contract.
Solidity:
event NewEvent(address indexed contractAddress, address newBOPAddress, address payer, uint commitThreshold, bool ...
- 71
6
votes
2
answers
648
views
How to access dynamic list from web3?
In my application players can create and join games. I store every game in a mapping(uint => Game), and send out a GameCreated event whenever a game is created. My issue is efficiently getting a list ...
- 106
6
votes
2
answers
2k
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Contract creation gas cost depends on code in library function?
I have a contract fooContract which is using a fooLib library, calling fooLib.foo(LibStruct storage param)
The transaction cost to create fooContract seems to depend on the code in the fooLib.foo() ...
- 1,221
6
votes
1
answer
2k
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Solidity: How could I decrease gas usage of complex structs?
Struct is very expensive as labelled here: It seems extremely expensive when storing struct type.
https://www.cryptocompare.com/coins/guides/what-is-the-gas-in-ethereum/:
sstore 100 Paid ...
- 8,298
5
votes
0
answers
53
views
Best way to store and verify data onchain for offchain data integrity?
I have a web2 application that stores some information in database rows,
however, I would like to store this information on-chain for data integrity, particularly on polygon.
What is the best way to ...
- 151
5
votes
1
answer
398
views
web3j is not generating struct inside my solidity contract
I have a struct Question in my smart contract. After generating the java wrapper class of my smart contract using web3j, Inside the wrapper class Question is not recognized, looks like web3j is not ...
- 61
5
votes
1
answer
126
views
Metadata not showing on opensea
I have a problem with a simple nft program i did in order to learn more about ERC721.
this is the code:
// SPDX-License-Identifier: MIT
pragma solidity ^0.8.0;
import "@openzeppelin/contracts/...
- 51
5
votes
2
answers
424
views
How would an nft marketplace structure their smart contracts to pay out "creator shares"?
This may be a noob question, but does any know how a market like Nifty or any similar nft marketplace actually implement paying a "creator share" or royalty back to the original creator ...
5
votes
0
answers
966
views
bitwise multiplication to reduce gas cost
This is the multiplication method from the SafeMath library.
/**
* @dev Returns the multiplication of two unsigned integers, reverting on
* overflow.
*
* Counterpart to Solidity's `*` operator.
*
* ...
- 921
5
votes
0
answers
960
views
How to mimic abi.encodeWithSignature in web3?
I have the following function that I would like to test.
function createPlanet(bytes memory _data) public returns (address) {
emit ProxyCreated(planetImplementation);
emit ...
- 85
5
votes
0
answers
217
views
How can i do 2^0.3 (exponent below 1) using integers?
simple problem, but i can't seem to wrap my head around it in solidity.
how can i do 2^0.3 (exponent smaller then 1) in solidity using integers.
thanks in advance
K.
5
votes
1
answer
686
views
Truffle test fails to call the base function, wants the override
I have an extended ERC20 contract with ERC827 functions, which are overrides of ERC20 with an extra callback parameter.
I have these two pairs of base/override functions:
Base:
function ...
- 1,117
5
votes
1
answer
352
views
Interfaces and gas savings
Does it save gas to link to the bytecode of an interface? I tested this is solidity remix and using the interface to link bytecode instead of the full contract, didn't seem to reduce any gas costs for ...
- 579
4
votes
0
answers
78
views
Hardhat and foundry, contract bytecode different
I'm developing a contract in hardhat project. But now I want to write test by foundry. My problem is I'm using create2, but when running contract by hardhat and foundry they gave different addresses. ...
- 163
4
votes
0
answers
138
views
Why does Ownable.sol from OpenZeppelin rely so much on the use of functions?
I wondered why OpenZeppelin relies so much on the use of functions when, at first glance, they seem unnecessary for such elementary operations. For example, take the Ownable.sol contract. Why isn't ...
- 51
4
votes
0
answers
415
views
Block scoping in Solidity to avoid "Stack too deep error"
I have a quite big function with 16+ local variables which produces the infamous Stack too deep error. To handle this bad boy I have searched for the possible solutions and ended up using scopes.
...
- 304
4
votes
0
answers
402
views
Decode parameters on contract creation or constructor parameters
I want to decode parameters passed to contract constructor. Even if i used the ABI of the contract, it doesn't seem to resolve the parameters used.
Here is the transaction trace out put
https://gist....
4
votes
1
answer
422
views
which wallet supports access list(eip-2930)
I am trying to use Access List feature - Link here
I am using also ethers.js..
It seems like that ethers.js supports passing access list, but Metamask doesn't yet support this feature.
do you know any ...
- 1,135
4
votes
2
answers
271
views
How do I initialize an array of Structs
I would like to initialize an array of structs:
struct person {
string firstName;
string lastName;
}
person[3] family = [
person("Will", "Smith"),
person("Jada", &...
- 171
4
votes
0
answers
107
views
Ensuring the atomicity of multiple transactions
I am new to solidity and have been creating single (both basic and complex) transactions. However, I have a question which I couldn't come up with a solution.
How can I create 2 (or more) transactions ...
- 41
4
votes
3
answers
1k
views
Uniswap Router deployment error: "UniswapV2Router02" -- Cannot create instance of UniswapV2Router02; no code at address 0xxxxxxxxx
I am trying to fork Uniswap and deploy on Ropsten testnet for educational and testing purposes. From what I gathered, it seems that we need to first deploy the UniswapV2Factory contract, followed by ...
- 41
4
votes
0
answers
219
views
how to calculate the message part for pedersen hash in solidity
I am trying to implement pedersen hash using solidity. Is it possible to implement and how to split the message according to the conditions of pedersen hash.
- 41
4
votes
5
answers
12k
views
How do I inject Web3 into Remix IDE?
when going on to the remix IDE, i get the error
No injected Web3 provider found. Make sure your provider (e.g. MetaMask) is active and running (when recently activated you may have to reload the page)....
- 71
4
votes
2
answers
12k
views
can't verify contract on etherscan (But we were unable to locate a matching bytecode (err_code_2))
so i'm trying to verify a contract on rinkeby and ropsten...
getting the same error of
"Compiler debug log:
Error! Unable to generate Contract ByteCode and ABI
Found the following ContractName(s) ...
- 146
4
votes
0
answers
431
views
Solidity Contract and Library difference
I am learning to program Solidity and just playing around with it in remix.
I am creating compiling the following code in Solidity:
pragma solidity >=0.4.22 <0.6.0;
contract Ballot {
...
- 51
4
votes
0
answers
164
views
VM revert on Scalar Multiplication in pre-compiled contracts
I tried to build a wrapper around the precompiled contracts as follows:
https://gist.github.com/AlexXiong97/9c24bbd4541323a61fa63100860a5f89
If you paste it into Remix and deploy it, inputting any (...
- 181
4
votes
1
answer
474
views
Order of evaluation: an example
In the Solidity documentation is stated that:
The evaluation order of expressions is not specified (more formally, the order in which the children of one node in the expression tree are evaluated ...
- 1,874
4
votes
1
answer
268
views
Estimated gas is always low
web3.eth.estimateGas is always calculating low gas for the transaction. Here is a reference to a trasaction in ropsten.
https://ropsten.etherscan.io/tx/...
4
votes
0
answers
3k
views
Getting Json file from remix
I have been deploying contracts on rinkeby but we are almost done to go to mainnet.
I have been comparing deployments with truffle and remix and there is a huge difference in gas uses, so I would ...
- 153
4
votes
2
answers
2k
views
Declaring a memory array of storage pointers in Solidity
I would like to declare a variable as a memory array of pointers to storage arrays of uint256.
For example:
pragma solidity ^0.4.24;
contract A
{
uint256[] public array0;
uint256[] public ...
- 10.2k
4
votes
1
answer
743
views
Does delegatecall pass up the events?
I want to use delegatecall in one function to populate an event from the contract I'm calling. Here's a minimal example:
contract Caller {
address public callee;
function Caller(address ...
- 350
4
votes
2
answers
674
views
Smart Contract firing send ether transaction that's not in the contract
I need some help with my smart contract, here's the smart contract code
pragma solidity ^0.4.18;
contract UserToken {
mapping (bytes32 => uint8) public tokenBalance;
bytes32[] public ...
- 41
4
votes
0
answers
818
views
Truffle migrate Error Invalid number of arguments to Solidity function
Truffle 4.0.1
I've got a contract declared "is Pausable" (OpenZeppelin framework) and I want to pause it as part of the deployment logic.
I'm getting an error, however, when invoking pause()
Error: ...
- 241
4
votes
0
answers
127
views
Autorefill isn't working on Improved Coin code
I've been trying to write a token contract with the autorefill function, but perhaps the code for the token example on the ethereum website is somewhat outdated, because it isn't working.
Did anybody ...
- 41
4
votes
3
answers
3k
views
Correctly deploying contracts with web3 1.0 and testrpc (invalid opcode error)
I followed the following tutorial:
https://medium.com/@mvmurthy/full-stack-hello-world-voting-ethereum-dapp-tutorial-part-1-40d2d0d807c2
Now this tutorial is not using the recent version of web3 but ...
- 41
4
votes
1
answer
2k
views
Truffle Bytecode Different from Etherscan Bytecode
I am having difficulty verifying my contract code on Etherscan using the code generated by Truffle.
Using Etherscan VerifyContract V1: https://rinkeby.etherscan.io/verifyContract
Truffle produced ...
- 1,167