Syscalls Overview

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Overview

Syscalls are invoked via the SYSCALL opcode followed by a 4-byte identifier. The identifier is the first 4 bytes of SHA256(syscall_name_string). For example, System.Storage.Get has the ID derived from SHA256("System.Storage.Get").

The compiler maps Solidity patterns to the appropriate syscalls during code generation. State variable reads become System.Storage.Get, event emissions become System.Runtime.Notify, and cross-contract calls become System.Contract.Call.

The devpack provides two levels of access:

• Direct wrappers — Syscalls.sol exposes the supported syscall surface as typed Solidity functions.
• Ergonomic libraries — Storage.sol, Runtime.sol, and Neo.sol provide higher-level APIs built on top of the raw syscalls.

import "devpack/contracts/Syscalls.sol";

// Direct syscall access
address caller = Syscalls.getCallingScriptHash();

// Or use the ergonomic wrapper
import "devpack/libraries/Runtime.sol";
bool authorized = Runtime.checkWitness(caller);