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

It allows arithmetic to use fewer storage slots

Answer

It converts all math to bitwise operations automatically

Answer

It disables the ABI encoder for numeric types

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

Late reverts cost a fixed 21,000 gas penalty

Answer

Early reverts bypass the ABI decoder

Answer

The EVM charges double gas for late reverts

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

The caller steals gas from the callee by setting a low gas limit

Answer

Gas griefing is a compiler bug affecting loops

Answer

It occurs when two contracts mutually call each other

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

Deployment and calls both cost exactly 21,000 gas base

Answer

Function calls on existing contracts are always free

Answer

Deployment costs are measured in ETH, not gas

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 skip the revert opcode entirely

Answer

Custom errors are stored in a separate cheaper memory area

Answer

String messages are charged at 20,000 gas per character

Question 6

What gas optimization does 'lazy initialization' or 'default value avoidance' provide in Solidity?

Accepted Answer

Avoiding writing 0 to storage saves 20,000 gas because SSTORE to a non-zero slot costs less than creating a new slot

Answer

Zero values are stored in calldata instead of storage

Answer

Default values are inlined by the optimizer as constants

Answer

Variables initialized to zero skip the constructor