Update Rust tolchains by deuszx · Pull Request #5554 · linera-io/linera-protocol

deuszx · 2026-03-02T09:34:09Z

Motivation

The project has been pinned to Rust 1.86.0 stable / nightly-2025-03-21 for a long time. Bumping to a recent toolchain was blocked by three independent issues:

Applications don't load with Rust 1.87 or later #4742: Rust 1.87+ emits Wasm bulk-memory opcodes (prefix 0xFC) that linera-wasm-instrument (backed by parity-wasm) could not parse, causing applications to fail to load.
Upgrade to Wasmer ~5~ ~6~ 7 #4203: Rust 1.89+ removed __rust_probestack from compiler-builtins, breaking the Wasmer VM build.
Don't enable shared memory by default with Wasm atomics rust-lang/rust#147225: Rust 1.92+ made -Z wasm_c_abi=spec a hard error, and atomics no longer auto-enable shared memory for the web target.

Proposal

Bump stable toolchain to 1.93.1 and nightly to nightly-2026-03-01.

Dependency fixes (git branches, until crates.io releases are available)

linera-wasm-instrument → linera-io/wasm-instrument@bulk-memory-support: enables bulk-memory support in parity-wasm so it can parse opcode 0xFC. Also enable the bulk feature in linera-execution so
the instrumentation pass handles these opcodes. Fixes Applications don't load with Rust 1.87 or later #4742.
linera-wasmer{,-compiler,-compiler-singlepass,-vm} → linera-io/wasmer@fix-rust-probestack: vendors __rust_probestack in linera-wasmer-vm using rustversion to conditionally provide the symbol only
on Rust 1.89+. Addresses the Wasmer portion of Upgrade to Wasmer ~5~ ~6~ 7 #4203.
ruzstd: unpin from =0.8.1 to 0.8 (the build failure on 0.8.2 that motivated the pin is fixed in newer Rust).

Custom `wasm32-mvp` target for testnet_conway compatibility

Rust 1.93/LLVM 18 enables bulk-memory, bulk-memory-opt, and nontrapping-fptoint as default features for wasm32-unknown-unknown. All use the 0xFC opcode prefix, which testnet_conway validators
reject.

The standard -C target-feature=-bulk-memory,... flag is silently ignored by LLVM 18 when these features are part of the target's default feature set. A custom target JSON is the only reliable solution:

linera-service/wasm32-mvp.json: identical to wasm32-unknown-unknown except "features": "-bulk-memory,-bulk-memory-opt,-nontrapping-fptoint".
examples/.cargo/config.toml: configures -Zunstable-options, build-std = ["std", "panic_abort"], and json-target-spec = true so cargo build --target wasm32-mvp works in the examples workspace.
.cargo/config.toml: sets RUST_TARGET_PATH to linera-service so the custom target resolves anywhere in the repo.
CliWrapper::build_application: builds contracts using +nightly-2026-03-01 --target wasm32-mvp.json -Z build-std -Z json-target-spec, then copies output from target/wasm32-mvp/release/ to
target/wasm32-unknown-unknown/release/ so downstream code is unaffected. Also installs the nightly toolchain with rust-src on first run.
examples/rust-toolchain.toml: changed from a symlink to rust-toolchain.toml (stable) to a symlink to toolchains/nightly/rust-toolchain.toml (nightly), since -Z build-std and -Z json-target-spec
require nightly cargo.
Example README files updated to use --target wasm32-mvp in build commands.

Clippy / lint fixes

Various Clippy fixes required by the new toolchain:

Replace format!("{}", x) with format!("{x}") (clippy::uninlined_format_args)
Replace deprecated GenericArray::as_slice() with slice indexing &digest[..] in the llm example (sha3 API change)
Replace .index() with .enumerate() where flagged
Add cargo-machete ignores for half in llm and gen-nft (transitive dependency)
Reformat half workspace dependency for taplo compliance

Web target fix

Remove -Z wasm_c_abi=spec (hard error in Rust 1.92+) and add explicit shared-memory linker flags (-Wl,--shared-memory, -Wl,--max-memory=...) for the web target, since atomics no longer auto-enable shared
memory.

Test Plan

CI

Release Plan

TBD

Links

#5264

reviewer checklist

Bump the stable toolchain from 1.86.0 to 1.93.1 and the nightly toolchain to nightly-2026-02-23. This required three fixes: - Enable bulk memory support in wasm-instrument so parity-wasm can parse opcode 0xFC (bulk memory operations) that Rust 1.87+ emits in wasm output. Fixes #4742. - Vendor __rust_probestack in linera-wasmer-vm for Rust 1.89+ where the symbol is no longer exported from compiler-builtins. Addresses the wasmer build portion of #4203. - Remove -Z wasm_c_abi=spec (hard error in 1.92+) and add explicit shared-memory linker flags for the web target since atomics no longer auto-enable shared memory in Rust 1.92+. Also unpins ruzstd and updates wasm test fixtures and expected fuel counts for the new compiler output. Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

…chete - Replace deprecated `GenericArray::as_slice()` with `as_ref()` in llm service - Reformat half workspace dependency to multi-line (taplo requirement) - Move half to alphabetical position in workspace.dependencies - Add cargo-machete ignore for `half` in llm and gen-nft (transitive dep) Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

…hange Use &digest[..] slice indexing instead of .as_ref() to unambiguously yield &[u8] in assert_eq!, avoiding "type annotations needed" errors when the compiler can't infer the AsRef target type. Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

…ontracts Rust 1.93 enables bulk-memory and nontrapping-fptoint by default for wasm32-unknown-unknown (unlike 1.86), causing compiled contracts to emit opcode 0xFC which testnet_conway validators do not support. Add -C target-feature=-bulk-memory,-nontrapping-fptoint to .cargo/config.toml so all contracts built on this branch are compatible with testnet_conway validators. Re-enable +bulk-memory in web/.cargo/config.toml since the web client requires it for shared-memory threading support.

The RUSTFLAGS env var (e.g. "-D warnings" in CI) takes priority over [target.wasm32-unknown-unknown] rustflags in .cargo/config.toml, so the config-file fix was silently ignored in CI. Explicitly append -C target-feature=-bulk-memory,-nontrapping-fptoint to RUSTFLAGS in build_application so the 0xFC opcode suppression is always effective regardless of the calling environment.

…nway Rust 1.93/LLVM 18 added bulk-memory, bulk-memory-opt, and nontrapping-fptoint as default features for wasm32-unknown-unknown. All use opcode prefix 0xFC, which testnet_conway validators reject as an unknown opcode. The previous approach of -C target-feature=-bulk-memory,-nontrapping-fptoint is silently ignored by LLVM 18 when those features are part of the target's default feature set. A custom target JSON is the only reliable fix. wasm32-mvp.json is identical to wasm32-unknown-unknown except for: "features": "-bulk-memory,-bulk-memory-opt,-nontrapping-fptoint" build_application now builds with this custom target (using -Z build-std to also recompile stdlib from source without the disabled opcodes), then copies the wasm files to the standard wasm32-unknown-unknown/release/ directory so callers are unaffected. Also add a regression test that builds the fungible contract and verifies the output contains no 0xFC instructions (bulk-memory / nontrapping-fptoint) by disassembling with wasm2wat and checking for the instruction names. examples/rust-toolchain.toml is changed from a symlink to a real file specifying nightly, since -Z build-std and -Z json-target-spec require it. Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

And update README.md-s for readability.

Twey · 2026-03-09T14:23:28Z

.cargo/config.toml

 linker = "aarch64-linux-gnu-gcc"

+[env]
+# Makes `--target wasm32-mvp` resolve to linera-service/wasm32-mvp.json


Rather than using wasm32-mvp, let's add two targets that we can distinguish:

wasm32-linera-chain for on-chain applications (contract and service)

wasm32-unknown-js-web for the Web browser (@linera/client)

Then we can throw away the web features that are currently polluting our codebase.

(I'll suggest one target for both contract and service, even though it might be cleaner to separate them, because it eases compilation of applications for the end-user)

Twey · 2026-03-09T14:27:23Z

examples/rust-toolchain.toml

@@ -1 +1 @@
-../rust-toolchain.toml
+../toolchains/nightly/rust-toolchain.toml


I wonder if it's time to migrate wholesale to nightly Rust and forget about stable. Basically all our codepaths now depend on nightly features except for the CLI build, and having just the one Rust version would simplify our build a lot. (We can still forbid #![feature]s in the core codebase.)

Twey · 2026-03-09T14:29:49Z

linera-service/src/cli_wrappers/wallet.rs

+        // Write the custom target spec to a temporary file. The spec disables
+        // bulk-memory, bulk-memory-opt, and nontrapping-fptoint — opcodes that
+        // use the 0xFC prefix and are not supported by testnet_conway validators.
+        // Using a custom target JSON (rather than -C target-feature flags) is
+        // necessary because Rust 1.93/LLVM 18 ignores the flag for these features
+        // when they are part of the target's default feature set.


Can we not just add the target to the application template (linera-service/template)?

Twey · 2026-03-09T14:31:03Z

linera-service/src/cli_wrappers/wallet.rs

+        Command::new("rustup")
+            .args([
+                "toolchain",
+                "install",
+                WASM_NIGHTLY_TOOLCHAIN,
+                "--component",
+                "rust-src",
+            ])
+            .spawn_and_wait_for_stdout()


Please let's not rely on the presence of rustup and mutating the user's home directory! We should specify the relevant features in the toolchain file and if rustup is present it should do the right thing.

Twey · 2026-03-09T14:31:30Z

linera-service/src/cli_wrappers/wallet.rs

        Command::new("cargo")
-            .current_dir(self.path_provider.path())
+            .current_dir(path)
+            .arg(format!("+{WASM_NIGHTLY_TOOLCHAIN}"))


As above, this should also be unnecessary if the toolchain file is set up correctly.

Twey · 2026-03-09T14:34:14Z

This PR is muddied a lot by the warning cleanups. Can we add them to a separate PR? is_multiple_of might require some conditional-compilation finagling (or I guess just that one can stay here — it's small) but the rest I think is backward-compatible.

deuszx · 2026-03-10T11:36:40Z

Being superseeded by #5646 and #5650

deuszx and others added 3 commits March 2, 2026 09:52

Clippy

488b867

Regenerate lock files

c6da5f2

deuszx force-pushed the issue-5264 branch from 0c619b4 to c6da5f2 Compare March 2, 2026 14:40

deuszx and others added 13 commits March 2, 2026 15:49

Merge remote-tracking branch 'origin/testnet_conway' into issue-5264

6b0861a

Fix compilation

b4cd98b

Clippy

c99dda3

Bump nightly toolchain

53cdf1b

Replace index() with enumerate

111348e

Update README files

f56cc81

Add new target to .cargo/config.toml

1870d00

And update README.md-s for readability.

RM test that cna't run in the CI

c4f1921

deuszx force-pushed the issue-5264 branch from 9c51a5e to c4f1921 Compare March 3, 2026 10:18

Install the toolchain in CliWrapper::build_application

607c94b

Twey reviewed Mar 9, 2026

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deuszx closed this Mar 10, 2026

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Update Rust tolchains#5554

Update Rust tolchains#5554
deuszx wants to merge 17 commits intotestnet_conwayfrom
issue-5264

deuszx commented Mar 2, 2026 •

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		@@ -1 +1 @@
		../rust-toolchain.toml No newline at end of file
		../toolchains/nightly/rust-toolchain.toml No newline at end of file

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Motivation

Proposal

Dependency fixes (git branches, until crates.io releases are available)

Custom wasm32-mvp target for testnet_conway compatibility

Clippy / lint fixes

Web target fix

Test Plan

Release Plan

Links

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deuszx commented Mar 2, 2026 •

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Custom `wasm32-mvp` target for testnet_conway compatibility

deuszx commented Mar 10, 2026 •

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