0.13.0

• motoko (moc)

  • Added a new primitive cyclesBurn : <system> Nat -> Nat for burning the canister's cycles
    programmatically (#4690).

  • For beta testing: Support enhanced orthogonal persistence, enabled with new moc flag --enhanced-orthogonal-persistence (#4193).

    This implements scalable and efficient orthogonal persistence (stable variables) for Motoko:

    • The Wasm main memory (heap) is retained on upgrade with new program versions directly picking up this state.
    • The Wasm main memory has been extended to 64-bit to scale as large as stable memory in the future.
    • The runtime system checks that data changes of new program versions are compatible with the old state.

    Implications:

    • Upgrades become extremely fast, only depending on the number of types, not on the number of heap objects.
    • Upgrades will no longer hit the IC instruction limit, even for maximum heap usage.
    • The change to 64-bit increases the memory demand on the heap, in worst case by a factor of two.
    • For step-wise release handling, the IC initially only offers a limited capacity of the 64-bit space (e.g. 4GB or 6GB), that will be gradually increased in future to the capacity of stable memory.
    • There is moderate performance regression of around 10% for normal execution due to combined related features (precise tagging, change to incremental GC, and handling of compile-time-known data).
    • The garbage collector is fixed to incremental GC and cannot be chosen.
    • Float.format(#hex prec, x) is no longer supported (expected to be very rarely used in practice).
    • The debug print format of NaN changes (originally nan).

    To activate enhanced orthogonal persistence under dfx, the following command-line argument needs to be specified in dfx.json:

    ...
      "type" : "motoko"
      ...
      "args" : "--enhanced-orthogonal-persistence"
    ...
    

    BREAKING CHANGE (Minor): changes some aspects of Float formatting.

    For more information, see:

    • The Motoko design documentation design/OrthogonalPersistence.md
    • The Motoko user documentation doc/md/canister-maintenance/upgrades.md.

  • Candid decoding: impose an upper limit on the number of values decoded or skipped in a single candid payload,
    as a linear function, max_values, of binary payload size.

      max_values(blob) = (blob.size() * numerator)/denominator + bias
    

    The current default settings are {numerator = 1; denominator = 1; bias = 1024 }, allowing a maximum
    of 1024 values plus one additional value per byte in the payload.

    While hopefully not required, the constant factors can be read/modified using system functions:

    • Prim.setCandidLimits: <system>{numerator : Nat32; denominator : Nat32; bias : Nat32 } -> ()
    • Prim.getCandidLimits: <system>() -> {numerator : Nat32; denominator : Nat32; bias : Nat32 }