Filecoin actors

This repo is the specification of the Filecoin builtin actors, in the form of executable code.

This is a companion to the rest of the Filecoin Specification, but also directly usable by Go implementations of Filecoin.

Versioning

Releases of this repo follow semantic versioning rules, with consideration of distributed state machines.

The major version will remain 0 or 1 for the forseeable future. We do not bump the major version every time there's a backwards-incompatible change in state machine evaluation, or actor interfaces, because this interacts very poorly with Go's module resolution, requiring a change of all import paths. After 1.0 we may consider using the major version number to version the Runtime interface, which is the link between the actors and the system in which they are embedded.
A minor version change indicates a backwards-incompatible change in the state machine evaluation, including actor exported methods or constant values, while retaining compatibility of the Runtime interface. This means that the same sequence of messages might produce different states at two different versions. In a blockchain, this would usually require a coordinated network upgrade or "hard fork". After 1.0, a minor version change may alter behaviour but not exported code or actor interfaces.
A patch version change may alter state evaluation (but not exported code or actor interfaces). After 1.0, a patch version change indicates a backward compatible fix or improvement that doesn't change state evaluation semantics or exported interfaces.

This repository is dual-licensed under Apache 2.0 and MIT terms.