Runtime Syscalls

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Runtime API

Runtime syscalls provide access to execution context, authorization, notifications, and platform metadata.

Syscall Name	Gas Cost	Description	Devpack Wrapper
System.Runtime.GetTrigger	1	Get execution trigger type	Syscalls.getTrigger()
System.Runtime.Platform	1	Get platform string ("NEO")	Syscalls.getPlatform()
System.Runtime.GetNetwork	1	Get network magic number	Syscalls.getNetwork()
System.Runtime.GetAddressVersion	1	Get address version byte	Syscalls.getAddressVersion()
System.Runtime.GetTime	1	Get current block timestamp (ms)	Syscalls.getTime()
System.Runtime.GetScriptContainer	1	Get transaction container	Syscalls.getScriptContainer()
System.Runtime.GetExecutingScriptHash	1	Get current contract hash	Syscalls.getExecutingScriptHash()
System.Runtime.GetCallingScriptHash	1	Get caller contract hash	Syscalls.getCallingScriptHash()
System.Runtime.GetEntryScriptHash	1	Get entry point hash	Syscalls.getEntryScriptHash()
System.Runtime.LoadScript	1	Registered but intentionally unsupported in the embedded runtime; use System.Contract.Call	Syscalls.loadScript(script, flags, args)
System.Runtime.CheckWitness	200	Verify witness authorization	Syscalls.checkWitness(hash)
System.Runtime.GetInvocationCounter	1	Get call count for current contract	Syscalls.getInvocationCounter()
System.Runtime.GetRandom	50	Get deterministic random number	Syscalls.getCurrentRandom()
System.Runtime.Log	1	Emit log message	Syscalls.log(message)
System.Runtime.Notify	1	Emit notification (event)	Syscalls.notify(data)
System.Runtime.GetNotifications	1	Embedded runtime returns []; notification lookup state is not exposed	Syscalls.getNotifications()
System.Runtime.GasLeft	1	Get remaining GAS	Syscalls.gasLeft()
System.Runtime.BurnGas	1	Burn specified GAS amount	Syscalls.burnGas(amount)
System.Runtime.CurrentSigners	1	Embedded runtime returns []; transaction signers are not modeled	Syscalls.getCurrentSigners()
System.Runtime.GetMsgValue	1	Get host-injected Solidity msg.value	Compiler runtime intrinsic

Example Usage

import "devpack/contracts/Syscalls.sol";

contract Guarded {
    address public owner;

    modifier onlyOwner() {
        // CheckWitness verifies the transaction includes a valid
        // signature for the given address (200 GAS units)
        require(Syscalls.checkWitness(owner), "unauthorized");
        _;
    }

    function sensitiveAction() external onlyOwner {
        // Only executes if the transaction signer controls `owner`
        Syscalls.log("sensitiveAction executed");
    }

    function getExecutionInfo() external view returns (
        address executing,
        address caller,
        uint256 timestamp,
        uint256 remainingGas
    ) {
        executing = Syscalls.getExecutingScriptHash();  // address(this)
        caller = Syscalls.getCallingScriptHash();        // msg.sender
        timestamp = Syscalls.getTime();                  // block.timestamp
        remainingGas = Syscalls.gasLeft();               // gasleft()
    }
}

Gas Cost Guidance

CheckWitness Gas Cost

System.Runtime.CheckWitness costs 200 GAS units — the most expensive runtime syscall. It performs cryptographic signature verification against the transaction's witness list. Avoid calling it in tight loops. Cache the result in a local variable when you need to check the same witness multiple times within a single execution.