Solidity Solidity Gas Optimization 3

Question 1

What is the gas benefit of using `unchecked` arithmetic blocks in Solidity 0.8+?

Accepted Answer

It skips the automatic overflow/underflow checks, saving ~20 gas per operation

Answer

Wrapping arithmetic in `unchecked {}` disables the compiler-inserted overflow checks, saving gas when you have already proven the values cannot overflow.

Question 2

Why is it more gas-efficient to revert early in a function rather than at the end?

Accepted Answer

Reverting early returns unused gas to the caller before expensive operations execute

Answer

Gas is consumed as each opcode executes; reverting before expensive storage reads/writes returns the remaining gas unspent.

Question 3

What is 'gas griefing' in the context of forwarding gas with `call` in Solidity?

Accepted Answer

A malicious callee can consume all forwarded gas, causing the caller to run out and revert

Answer

When a contract forwards all available gas to an external call, a malicious recipient can burn it all, forcing the calling contract to revert due to out-of-gas.

Question 4

What is the gas cost difference between deploying a contract and calling a function on an existing contract?

Accepted Answer

Deployment costs at least 32,000 base gas plus code storage; function calls cost 21,000 base plus execution

Answer

Contract creation has a base cost of 32,000 gas plus 200 gas per byte of bytecode stored, making deployment significantly more expensive than function calls.

Question 5

How do Solidity custom errors (introduced in 0.8.4) save gas compared to `require` with string messages?

Accepted Answer

Custom errors encode only a 4-byte selector in revert data, while string messages store and return the full string

Answer

Custom errors revert with just a 4-byte function selector (plus encoded parameters), whereas string error messages cost gas to encode, store, and return.

Solidity Practice Test

Solidity Practice Test

Solidity Solidity Gas Optimization 3