Syscalls and Devpack
The compiler emits Neo syscalls and native contract calls for common Solidity constructs. The devpack exposes the same runtime surface for explicit contracts.
Solidity to Neo Runtime Calls
| Solidity Construct | Neo Runtime Call | Notes |
|---|---|---|
msg.sender | System.Runtime.GetCallingScriptHash | Immediate caller script hash or transaction signer; some internal/self-offset runtime paths inject a direct-caller override. |
address(this) | System.Runtime.GetExecutingScriptHash | Current contract script hash. |
block.timestamp | System.Runtime.GetTime | Neo milliseconds normalized to seconds. |
block.number | Ledger.currentIndex | Native contract call through System.Contract.Call. |
gasleft() | System.Runtime.GasLeft | Remaining invocation GAS. |
| State variable read | System.Storage.Get | Key derived from state variable name. |
| State variable write | System.Storage.Put | Key derived from state variable name. |
mapping[key] read/write | System.Storage.Get / System.Storage.Put | Key derived by iterative SHA256 hashing. |
emit Event(...) | System.Runtime.Notify | Event name plus serialized arguments. |
Runtime.checkWitness(addr) | System.Runtime.CheckWitness | Account witness verification. |
address(target).call(...) | System.Contract.Call | Cross-contract invocation. |
keccak256(...) | CryptoLib.keccak256 | Native contract call. |
sha256(...) | CryptoLib.sha256 | Native contract call. |
Devpack Layers
| Layer | Import | Use |
|---|---|---|
| Low-level syscalls | devpack/contracts/Syscalls.sol | Typed wrappers for direct Neo N3 syscall access. |
| Runtime helpers | devpack/libraries/Runtime.sol | Witness checks, time, logging, notifications, and execution context. |
| Storage helpers | devpack/libraries/Storage.sol | Typed storage accessors, iterator helpers, mapping and array keys. |
| Native contract helpers | devpack/libraries/Neo.sol and related wrappers | GAS, NEO, Ledger, Policy, Oracle, CryptoLib, and ContractManagement calls. |
| Standards | devpack/standards/*.sol | NEP token and lifecycle standard implementations. |
When to Use Devpack Calls
Use normal Solidity syntax for common constructs such as state variables, events, and typed contract calls. Use devpack wrappers when your contract needs Neo-specific functionality, direct native contract access, or explicit witness and storage utilities.