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Version: 2.6.0

Migration guide to v2.6.0 from 2.*

Odra v2.6.0 does not introduce any breaking changes in the smart contract code. However, upgrading requires bumping cargo-odra to v0.1.7 in order to keep the build pipeline working with recent Rust toolchains.

Update cargo-odra​

Install the new version:

cargo install cargo-odra --version 0.1.7 --force --locked

Verify the installation:

cargo odra --version

Why the update is required​

cargo-odra runs wasm-opt (from Binaryen) as a post-processing step on every compiled contract. Starting with nightly-2025-02-18 and stable 1.87.0, Rust ships with LLVM 20, which enables the WebAssembly bulk-memory feature by default. This means rustc now emits memory.copy and memory.fill instructions directly, whereas older LLVM versions lowered them to inline loops or libc calls.

The version of wasm-opt bundled with cargo-odra does not accept these instructions unless it is told to both enable the bulk-memory feature and lower the LLVM-style memory intrinsics. As a result, building an Odra contract with a newer toolchain using an older cargo-odra fails during the wasm-opt step.

cargo-odra v0.1.7 detects the toolchain date and, when it is 2025-02-17 or later, automatically passes the following additional flags to wasm-opt:

  • --enable-bulk-memory
  • --llvm-memory-copy-fill-lowering

Older toolchains are unaffected — only --signext-lowering is applied, exactly as before.

Do I need to change anything else?​

No. There are no changes required in your contract code, tests, or Odra.toml. Once cargo-odra is updated, running cargo odra build and cargo odra test will work across both older and newer Rust toolchains without any further action.

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