Blockchain Quiz

Unbounded loops that depend on storage or user-controlled arrays can exhaust gas and render functions uncallable. Attackers can intentionally cause denial-of-service through loop amplification. Good design avoids external iteration

String comparison requires hashing or byte-by-byte checks, both of which are expensive in the EVM model. It also introduces risk when mixed with packed encodings. Developers instead rely on enums or hashed IDs.

Memory follows a quadratic cost function, meaning costs rise rapidly as the memory footprint grows. Careless array allocations can suddenly inflate execution cost. This is a frequent root cause of gas blowups in audits.

PUSH0 provides a zero literal without consuming calldata or memory. This reduces bytecode size and simplifies stack management. It's extremely helpful in tight loops and assembly-heavy contracts.

State shadowing happens when a derived contract redeclares a state variable with the same name as a parent. This creates storage misalignment and unexpected slot overwrites. Auditors treat this as a major upgradeability and correctness risk.

Calldata avoids copying user inputs into memory, significantly reducing gas usage for large payloads. Router contracts receive untrusted inputs, so avoiding memory expansion is both cheaper and safer. This is why AMMs and DEX routers heavily rely on calldata

Silent reverts hide failure reasons, making debugging and validation difficult. They also open the door for inconsistent execution paths

REVERT allows returning structured revert data back to the caller, which improves debugging and interface guarantees. INVALID terminates execution with no return payload. This distinction is crucial for protocols relying on bubble-up error messaging.

EXTCODESIZE checks if the target has code deployed. It helps detect contracts vs EOAs in validation logic

Multi-step operations can leave the contract in a partially updated state if execution halts. Attackers exploit these interim states to bypass checks.

If the implementation contract is self-destructed, proxies break permanently or redirect unexpectedly. This creates bricked contracts and undefined behavior

RETURNDATASIZE ensures the caller knows exactly how many bytes were returned. It prevents incorrect assumptions and truncation bugs during low-level calls.

Storage is the most expensive resource in the EVM. Large arrays result in high operational cost and poor long-term scalability.

Miners can adjust timestamps within a reasonable range, enabling subtle manipulation. This can affect auctions, lotteries, and reward systems

delegatecall executes callee code in the caller’s storage context, leading to storage collisions and privilege escalation. This is a key attack vector in proxy contracts.

MSTORE triggers memory expansion when writing to higher memory slots. Memory grows quadratically, so developers must understand how loops and large arrays impact gas.

If the constructor reverts, the entire deployment fails and no contract is created. This prevents partially-initialized smart contracts from being pushed on-chain

EXTCODEHASH returns the hash of a contract’s deployed bytecode, allowing detection of code changes or empty accounts. Auditors use it to verify contract identity and defend against unexpected contract replacement patterns

immutable variables are stored directly in bytecode, not in storage, reducing runtime gas and preventing accidental overwrites. It is a common optimization technique in gas-efficient contract design.

When users mint again after the first drop, it shows they see long-term value in the project. Repeat minting is a strong signal of community trust.