Solidity to Syscall Mapping

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Automatic Lowering

The compiler automatically translates standard Solidity constructs to the corresponding NeoVM syscalls. No manual syscall invocation is needed for these patterns.

For a shorter reader guide that separates runtime calls from devpack usage, see Syscalls and Devpack.

Mapping Table

Solidity Construct	Syscall / Neo Call	Notes
msg.sender	System.Runtime.GetCallingScriptHash	Returns caller's script hash (UInt160)
address(this)	System.Runtime.GetExecutingScriptHash	Returns current contract's script hash
block.timestamp	System.Runtime.GetTime	Milliseconds, normalized to seconds
block.number	Ledger.currentIndex (native call)	Not a syscall — uses System.Contract.Call
gasleft()	System.Runtime.GasLeft	Remaining GAS in current invocation
State variable read	System.Storage.Get	Key derived from variable name via SHA256
State variable write	System.Storage.Put	Key derived from variable name via SHA256
mapping[key] read	System.Storage.Get	Key = SHA256(serialize(key) || slot)
mapping[key] write	System.Storage.Put	Same derived key
emit Event(...)	System.Runtime.Notify	Event name + args as notification
require(Runtime.checkWitness(addr))	System.Runtime.CheckWitness	Witness verification (200 GAS)
address(target).call(...)	System.Contract.Call	Cross-contract invocation (10 GAS)
address(target).staticcall(...)	System.Contract.Call (read-only flags)	Read-only cross-contract call
keccak256(...)	CryptoLib.keccak256 (native call)	Via System.Contract.Call, not a syscall
sha256(...)	CryptoLib.sha256 (native call)	Via System.Contract.Call, not a syscall

Example Lowering

// What you write:
contract Example {
    mapping(address => uint256) public balances;
    event Transfer(address indexed from, address indexed to, uint256 amount);

    function transfer(address to, uint256 amount) external {
        require(Runtime.checkWitness(msg.sender), "unauthorized");
        balances[msg.sender] -= amount;
        balances[to] += amount;
        emit Transfer(msg.sender, to, amount);
    }
}

// What the compiler emits (pseudocode):
// 1. System.Runtime.CheckWitness(callingScriptHash)  — 200 GAS
// 2. System.Storage.GetContext()                      — 1 GAS
// 3. System.Storage.Get(ctx, derived_key_sender)      — 100 GAS
// 4. System.Storage.Put(ctx, derived_key_sender, new) — 1,000 GAS
// 5. System.Storage.Get(ctx, derived_key_to)          — 100 GAS
// 6. System.Storage.Put(ctx, derived_key_to, new)     — 1,000 GAS
// 7. System.Runtime.Notify("Transfer", [from, to, amount]) — 1 GAS
// Total: ~2,402 GAS units (syscalls only, excludes opcode costs)