Layout of Call Data

In Ethereum Solidity, calldata is a special, non-modifiable, non-persistent data location where function arguments are stored. Reading from calldata is significantly cheaper than loading those arguments into memory. EVM uses the CALLDATALOAD opcode to slice data from this contiguous byte array.

Calldata on NeoVM

💡 NeoVM Difference

NeoVM does not have a separate calldata region. All method arguments are simply pushed onto the execution stack by the Neo node prior to the contract's execution.

When the neo-devpack-solidity compiler encounters the calldata keyword in a Solidity contract, it treats the location identically to memory.

function process(bytes calldata inputData) external {
    // EVM: Accesses a specialized read-only execution region
    // NeoVM: The inputData is a standard ByteArray stack item loaded as a local variable
}

This means:

1. Source Compatibility: Existing Ethereum contracts that optimize for calldata will compile perfectly on Neo DevPack for Solidity.
2. Runtime Execution: At runtime, the data is just a standard stack item. There is no gas difference between memory and calldata on NeoVM.
3. Modifiability: While NeoVM stack items are technically mutable, the compiler still enforces Solidity's static analysis rules, preventing you from modifying a variable explicitly marked as calldata.