Questions tagged [contract-debugging]

questions for finding and squashing bugs in smart contracts and decentralized development

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find the exact error in solidity transaction programmatically

I know we can detect that the transaction is going to be failed with the "Out of gas" warning beforehand but is it possible to find the exact error before sending it to the blockchain. How can we ...
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1answer
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Getting a, “ReferenceError: artificats is not defined” - Error running a simple “approver” test

(Working from the Lynda Ethereum course) Running the test code below I get the following error: truffle tests Warning: Both truffle-config.js and truffle.js were found. Using truffle-config.js. ...
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1answer
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“TypeError” for a simple program causing failure to compile, “Type address is not implicitly convertible to expected type address payable.”

This is my first contract (working from Lynda course). Even when I use the supplied code I still age this error for the following code with I try to compile: TypeError: Type address is not implicitly ...
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1answer
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Information Regarding LASER and Ethereum

I was reading this article https://diligence.consensys.net/files/D1T2%20-%20Bernhard%20Mueller%20-%20Smashing%20Ethereum%20Smart%20Contracts%20for%20Fun%20and%20ACTUAL%20Profit.pdf and came across ...
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2answers
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Token Sale Smart Contract

I am new to Ethereium Block Chain and have been trying some code written in solidity as follows. pragma solidity ^0.5.0; import "./MyERC20Token.sol"; import "./ERC20Burnable.sol"; contract ...
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1answer
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Testing Smart Contract with multiple clients

After deploying a smart contract on Ropsten Testnet using Truffle framework, we can use truffle tests to do unit testing (create a client to interact with the deployed contract). My question is, how ...
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2answers
67 views

How to diagnose a “Error: Transaction has been reverted by the EVM”?

This the error intercepted from my javascript, using web3.js Error: Transaction has been reverted by the EVM: { "blockHash": "...
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1answer
58 views

Getting an 'invalid opcode' calling a solidty function from test file

im in the process of learning about ethereum and Solidity, and im having a problem calling a payable function from a test file. This is my contract pragma solidity >=0.4.22 <0.6.0; //pragma ...
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3answers
46 views

Revising Smart Contracts [closed]

If I create a Smart Contract that pays users for sharing their data, how can I ever update this smart contract in the case it has an error, or perhaps I wish to change the amount paid for data sharing?...
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1answer
32 views

Cannot transfer ownership of ERC20 contract

My contract source code likes below: contract StandardToken { uint256 totalSupply; ... } contract Ownable { address public owner; function Ownable() public { owner = msg.sender; } ...
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1answer
21 views

Why does declaring returns type bytes memory give a compiler error?

If we have the following code: pragma solidity >= 0.5; contract stringsContract { function takesTwo(string memory str, uint idx) public pure returns (bytes memory) { bytes memory ...
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1answer
41 views

Remix IDE: How to debug a contract having a function with a argument & for Loop

I am trying to debug a contract on Remix IDE: pragma solidity ^0.5.1; contract DebuggerSampleContract{ int counter = 10; function LoopCounter(int _input) public view returns (int) { int ...
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Sample Contracts for Testing Static Analysis Tools

I have to analyse some static Analysis tools against well documented vulnerabilities. My questions are ; Can we use the provided sample contracts (in above link) directly or not ? If not, then where ...
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1answer
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VM error: revert.The called function should be payable if you send value and the value you send should be less than your current balance

There is already a similar question, but it doesn't help me. So I ask this question again and expect something useful information. Two contracts named AccessControl.sol and Judge.sol. I've removed ...
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2answers
298 views

Install Old Solc Compiler Versions

I would like to compile older versions of solc contract source code using a solc compiler on my local machine. Is there a website from which to download old solc compilers? Google revealed a GitHub ...
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Address to create a contract

This query is for informational purposes, with something that has had me in doubt all night. I am trying to send a self-signed transaction for the creation of a contract My Tx transaction to send is ...
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1answer
29 views

Solidity. Find whether a key exists in a mapping. Then get its value

I have a simple mapping: mapping(address => string) professorsExam; How can I check if msg.sender is a key in this mapping, and if it is, get its value? If it isn't I should return something. ...
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15 views

Backward program analysis (like symbolic backward execution) tools for smart contracts

I know there are some backward program analysis tools for traditional softwares, but i wonder if there are already backward symbolic execution tools for smart contracts, or any tool that I can refer ...
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1answer
52 views

Solidity - Creating child contract

Recent code: pragma solidity ^0.5.11; pragma experimental ABIEncoderV2; contract Master { address Pi_C_Owner; address payable public NewAuctionPayable; //Hilfsvariable um ...
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1answer
67 views

Help me Understand the flow of this smart contract

I have 2 smart contract, below is the implementatin of them : 1) import "./MaintainableUpgradeabilityProxy.sol"; function _createProxy(address implementation, address serviceRegistry) internal ...
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1answer
32 views

Adding a payee to a donation contract. Error: Transaction reverted

Disclaimer: I'm a noob when it comes to programming altogether let alone smart contracts. I refactored this code that was written like three years ago so it could work with solidity 0.5.0. I deployed ...
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1answer
25 views

How can I debug a my Solidity smart contract with a GUI?

Is there any way to debug a Solidity smart contract with a GUI, like remix? How can I do it for both testnets and mainnet?
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1answer
20 views

What are the ways to call a smart contract function during development?

What are the ways to call a smart contract function during development using Truffle simulated VM with a GUI interface (like Remix or EtherScan offer)? I know I could use CLI options like Truffle ...
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0answers
14 views

Pulling EVM Bytecode of Contract Address [duplicate]

Is there a way to pull the EVM bytecode of a given contract address? Using Web3 perhaps? I believe using the web3.eth.Contract command may get access to the contract, but I am specifically looking ...
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15 views

Feeding a contract address to echidna

Simple question: Can I use echidna on a contract address? Like in mythril the command I use is myth -v4 analyze -1 -a 0xec410f642db4a2bcc4d7a69bc13b1165ebad3cea. I don't see any supporting ...
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2answers
382 views

How to check Ethereum smart contract info?

I want to know 3 things: Is an address a smart contract? Is this smart contract an ERC20 or ERC721 token? Is the Solidity code public?
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1answer
27 views

How to call a function with params and check them

I want to create a smart contract that users can send a number to and receive an amount of ether. function airdrop(uint val) public payable { require(airdrop == true); if (val == 0x31){ ...
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2answers
79 views

Verifying a Token Contract with Interface

I managed to deploy a token contract with interface on Kovan Testnet. Now I wanted to verify the code. However this is a bigger problem than I thought. The contract got successfully deployed to: ...
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0answers
52 views

Cannot execute contract in non-intaractive scripts

I want to deploy and to execute ERC-20 contract on geth with non-interactive scripts. But, it seems that non-interactive scripts and console shows different results. Enviroment ubuntu 18.04(docker ...
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1answer
37 views

I accidentally sent a token to a token contract. Can I get it back? $MWAT [closed]

community! Instead of transferring my ERC20 token $MWAT (RED PLATFORM) to my wallet, I accidentally sent it to the contract itself https://etherscan.io/tx/...
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2answers
76 views

ParserError: Expected pragma, import directive or contract /interface/library definition

In an attempt to compile my ABI and verify my contract, I am getting the following warning: "ParserError: Expected pragma, import directive or contract /interface/library definition" on the first line ...
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2answers
151 views

Web3 - Access return value of events

I want to get the value that my smart contract returns in javascript. Here is the contract. (version 0.4.25 - web3 version 1.2) pragma solidity ^0.4.25; contract SimpleStorage { uint public ...
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How to debug a mainnet transaction which uses Delegatecall without running a full node?

I need to debug a transaction which was reverted on mainnet. The problem with most Debuggers (including remix), is if there’s a ᴅᴇʟᴇɢᴀᴛᴇᴄᴀʟʟ in that case, they don’t attempt to load the target ...
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1answer
111 views

What is the “pre-commit” scheme to defeat TOD attack?

I am writing to inquire feasible strategies to defeat Transaction Ordering Dependence (TOD) bugs. I learned from the best practice guideline such that we can use a so-called "pre-committed" scheme ...
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1answer
65 views

How to trace the line where a tx failed in truffle tests?

I know about 0x's sol-compiler and sol-trace. I used them before and they do exactly what I'm looking for, but these modules bring significant overhead when used with truffle. Check out this file to ...
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2answers
41 views

what is the transferfrom event signature?

I am currently writing a code that list all types of transactions in a given contract . my plan is to just check for all logs whether the topics[0] == an event signature of a function. and now i am ...
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1answer
127 views

Sending value to a solidity contract method from web3 results in `Invalid Tuple Value` error

I'm sending values to a solidity 0.5.1 method using web3 and keep getting an invalid Tuple value error. Here's the relevant contract code: struct mystruct { bytes32 id; string str; } ...
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1answer
56 views

Token migration and IDEX smart contract problem

During a recent token migration from token A to token B, a large number of token A were held by a number of people in an IDEX address (where it was ready to trade). The IDEX address is part of a smart ...
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2answers
22 views

Mappings can not be assigned to error

I am trying to create a dividend function for my token. This is in the first part of the contract for my coin: mapping (address => uint256) private _SavedDividend; Here is the constructor code: ...
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1answer
38 views

The constructor should be payable if you send value. The transaction has been reverted to the initial state

I'm following a LinkedIn course on Solidity and creating a simple contract. Code below: I'm new to solidity so I'm not sure exactly where I'm going wrong but I get the following error: Transact to ...
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1answer
94 views

No matching declaration found after argument-dependent lookup in remix IDE

I'm getting this error in remix: "TypeError: No matching declaration found after argument-dependent lookup. require(_spender.call.value(msg.value)(_data)); ^-----^ " function approveAndCall(...
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0answers
46 views

web3j - getter for array of addresses

I have a contract which has a field registry which is an array of addresses, Also have a getter for this field: function getRegistry() view public returns (address[] memory){ return ...
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1answer
33 views

Using contract to create Child contracts (web3j Java wrapper)

I have a simple Parent contract that creates child contracts and stores their address. contract Parent { address[] public registry; function createChild () public { address newChild =...
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1answer
107 views

Contract function call error “TypeError: Cannot read property 'isMinter' of undefined” using Truffle tool

I deployed a ERC20Mintable token in truffle env(the .sol file is ERC20Mintable.sol). 2_mintable.js ============= Deploying 'ERC20Mintable' ------------------------- > transaction hash: ...
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1answer
20 views

Syntax Error & how pay( ) would execute without explicitly calling pay( )?

I am getting a syntax error in the following code: pragma solidity ^0.5.1; contract C { function pay(uint n, address payable d)public { d.send(n); } } contract D1 { uint ...
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1answer
136 views

How to test the fuctionality of a Bittrex-related smart contract?

I've got my hands on a smart contract related to the Bittrex exchange. I would like to deploy this smart contract to test the functionality but I don't know how to call the functions properly. My ...
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1answer
53 views

truffle won't run tests while initializing a global contract instance

I am testing my smart contract in truffle. I need to declare some global variables hence I did so outside 'it'. I also tried declaring a global contract instance that I can use in all test cases. ...
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0answers
31 views

how much structure variable does solidity support? [duplicate]

Error: "UnimplementedFeatureError: Variable inaccessible, too deep inside stack" code: contract create{ struct s{ string s1; string s2; string s3; string s4; ...
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4answers
326 views

Handling decimals in somewhat complex math

I'm a bit lost on what to do with the following calculation. The problem is that decimals are being round up/down, which obviously doesn't give me the result I desire. int totalValue = 275000; int ...
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1answer
226 views

Is it normal to have Invalid opcode in a contract?

I was debugging my smart contract, while I did not encounter an invalid opcode error, I saw a lot of invalid opcodes in my deployed contract. Screenshot is from remix debugger. Is it normal to have ...

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