Overview

In Qubic, smart contracts are implemented in a restricted variant of C++ and compiled into the Qubic Core executable.

To isolate contracts, access to other contracts and Core internals is only allowed via the QPI (Qubic Programming Interface), the sole external dependency permitted. Using libraries is forbidden. Contracts also cannot use insecure C++ features like pointers, low-level arrays (no bounds checking), or preprocessor directives. All memory is zero-initialized, so contracts never access uninitialized memory.

A contract has a state struct, containing all its data as member variables. The memory available to the contract is allocated statically, but extending the state will be possible between epochs through special EXPAND events.

Contract developers should note that some parts of the Qubic protocol are not yet implemented.

• Contract execution will eventually incur fees, paid from a fee reserve funded by QUs burned during the IPO and through ongoing burns. A contract must continue burning QUs to stay active—once the reserve is empty, it stops executing.

• In the future, managing contracts will also need to pay for ledger entries, so collecting fees during asset issuance is recommended.