ci: fuzz smoke step builds for the host triple and fails when the build fails

[avrabe]

I found this while verifying #1078 on main. The ci.yml Fuzz Testing job has never fuzzed anything.

Evidence. Job logs before #1078 (job 114071052937) and after it (114098537961) both show eight could not compile failures, one per target:

error: sanitizer is incompatible with statically linked libc, disable it using `-C target-feature=-crt-static`

After #1078 there is also can't find crate for core, because the pinned nightly has no musl std. Each cargo +nightly fuzz run … || true swallowed the failure, so the job stayed green.

Cause. taiki-e/install-action ships a musl build of cargo-fuzz, and cargo-fuzz defaults --target to the triple it was built for. The scheduled fuzz.yml is unaffected: it runs cargo install cargo-fuzz, which gives a gnu build, and that run fuzzes for real (for example artifact_ids: 11,470,701 runs in 901 s).

Fix (ci.yml only).

• host=$(rustc -vV | sed -n 's/^host: //p'), passed as --target to cargo fuzz build and cargo fuzz run.
• The build is a separate command under set -euo pipefail, so a build failure fails the job. A fuzz run's finding stays non-blocking, as before.
• cargo fuzz list no longer hides its errors.

Checks.

• On macOS, with the pinned nightly and --target aarch64-apple-darwin, every crate compiles. The link fails with ld: initializer pointer has no target, a known macOS SDK linker issue that does not occur on Linux.
• cargo fuzz build|run --target exists in cargo-fuzz.
• The workflow parses and yamllint reports 0 errors.

The job runs only on pushes to main (it is continue-on-error), so the evidence will be the post-merge run's log. I will check it for Fuzzing <target> followed by libFuzzer Done N runs lines.

Also seen, not addressed here. In fuzz.yml, the cli_argv and yaml_footguns jobs failed on the last run. They need a separate look: findings, or setup.

🤖 Generated with Claude Code

https://claude.ai/code/session_015HMQUV3u86jN2hmCtXNTc9

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.

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