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Solidity News Wednesday, July 11

Securify: Security Scanner for Ethereum Smart Contract

  • A contract is exposed to gas-dependent reentrancy if: (1) the amount of transferred ether depends on state that gets updated only after the transfer is made and (2) the amount of gas handed to the caller depends on amount of available gas.
  • The call instruction for ether transfer grants control over the transaction execution to the ether receiver while handing all available gas, and this allows the receiver to call the contract again (before its state is updated) to receive the same amount of ether again.
  • An attacker can repeat this process until the contract’s balance is drained.
  • The balance of the wallet is set to zero out only after it is transfered to the transaction sender.
  • This contract is vulnerable to a gas-dependent reentrancy because it uses the call.value() statement, which transfers all available gas to msg.sender and also it updates the state of the contract (setting the balance to zero) after the call statement is executed.

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Securify: Security Scanner for Ethereum Smart Contract

1st Solidity Gas Golfing Contest

  • The Solidity Gas Golfing Contest is a competition for Solidity coders to produce the most gas-efficient code they can for a series of straightforward challenges.
  • Anyone can enter by providing a valid Solidity contract to the submission form; the SGGC server will then compile and run your contract, and if it passes all the tests, will add it to the leaderboard.
  • For templates and documentation for each of the challenges, and test vectors to check your code against, download this truffle project or this embark project.
  • Note that the test vectors used by the SGGC server are different from those provided – so make sure your code runs as efficiently as possible on all inputs!
  • Source code for each challenge is kept on the server, and will be made available at the end of the contest.

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1st Solidity Gas Golfing Contest

Do modifiers work in interfaces

  • No, maybe with abstract contracts you can achieve something similar – – First of all to create an interface the keyword should be used (I used version 0.4.24 of solidity and the solidity documentation.
  • I played a little bit with your code and when you try to create a function in an interface with a modifier, like this: – – Therefore, apparently, you cannot enforce a modifier in an interface.
  • Maybe you can try with an abstract contract and the template method pattern: – – So when you create a concrete subcontract can specify the function: – – Obviously with abstract classes you can also avoid the function getOwner in this way: – – and so you can instantiate a…

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Do modifiers work in interfaces

Deploying dapp on ETH & ETC problem

  • I thought it would be cool to have my ETH dapp also on ETC blockchain.
  • It runs on ETH blockchain with no problem so I took a bytecode a let it deploy on ETC through mycrypto.com.
  • Are there any differences between how smart contracts work on ETC and ETH blockchain?

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Deploying dapp on ETH & ETC problem

Incorrect values being passed

  • I am trying to copy stored values using the following internal value.
  • However, the log does not return the correct values.
  • Instead, it returns the following: – – Why are the values incorrect?

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Incorrect values being passed

Check out my CryptoZombie Gareth!

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Check out my CryptoZombie Gareth!

Can a contract emit another contract’s event?

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Can a contract emit another contract’s event?

solidity – Get the public address & key associated with one of the Ganache accounts using Web3.js? – Ethereum Stack Exchange

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solidity – Get the public address & key associated with one of the Ganache accounts using Web3.js? – Ethereum Stack Exchange

solidity – ERC 721 rental contract – Ethereum Stack Exchange

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solidity – ERC 721 rental contract – Ethereum Stack Exchange

Discord – Free voice and text chat for gamers

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Discord – Free voice and text chat for gamers

Top Solidity Courses

Getting Started with Ethereum Solidity Development (6,530 students enrolled)

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Ethereum Blockchain Developer: Build Projects Using Solidity (10,937 students enrolled)

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Ethereum : Decentralized Application Design & Development (9,794 students enrolled)

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The Complete Ethereum Course: Get .001 Ether In Your Wallet (4,273 students enrolled)

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Compile Your First Ethereum Smart Contract With Solidity (245 students enrolled)

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  • Compile a basic smart contract
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Learn Solidity: Programming Language for Smart Contracts (3,153 students enrolled)

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  • Develop Ethereum Smart Contracts using Solidity
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