Compiling Wasm with Rust 1.70 leads to unsupported Wasm opcodes

[webmaster128]

When compiling a CosmWasm contract with Rust 1.70 (and above?) to Wasm, instructions are emitted that cause the following error:

Wasm bytecode could not be deserialized. Deserialization error: "Unknown opcode 192"

or

Wasm bytecode could not be deserialized. Deserialization error: "Unknown opcode 194"

This referes to C0-C4 in this overview, i.e. the sign extension of Wasm.

See also use-ink/cargo-contract#1139.

Until this resolved, using Rust 1.69.0 is the recommended way. This is also the version used in the latest rust-optimizer/workspace-optimizer.

[hashedone]

Also, keep an eye on: rust-lang/rust#109807

[aeryz]

We had this issue with the compiler versions 1.70+ but compiling with this command seem to fix it:

RUSTFLAGS='-C target-feature=-sign-ext -C link-arg=-s -C target-cpu=mvp' cargo -Z build-std=std,panic_abort -Z build-std-features=panic_immediate_abort build --release --lib --target wasm32-unknown-unknown

[webmaster128]

I think we just make sure to support the sign extension from 1.3 onwards

[mikedotexe]

Since I rarely do toolchain customization, thought I'd drop a comment on how I'm dealing with this. Perhaps saves someone a couple minutes:

rustup install 1.69.0
rustup default 1.69.0

# Then when things are ironed out, set it back
rustup default stable

[webmaster128]

Can you confirm that 1.69.0 works well? I just realized that the current rust-optimizer is on 1.68.2 and not yet 1.69.0. Is it safe to bump it to 1.69.0?

[mikedotexe]

Is it safe to bump it to 1.69.0?

Yes, I just double-checked on Juno testnet with a simple contract juno1vll4rksrtkemyvqxmff5a2r9s68px4alqud9wafvzm3m0c5ldm2s2ly243 using the 0.13.0 version from here https://hub.docker.com/layers/cosmwasm/rust-optimizer/0.13.0/images/sha256-2658caa839184c90b93e3ef5d5da0ab091f9e773492faa4b41b30f8973c62651?context=explore

Tested by optimizing, storing, instantiating, doing a contract execution and query, and confirming state changed as I expected.

[webmaster128]

Done in #1743. Will be shipped as part of 1.3.