[tamird]

GNU/Linux builders currently have to edit main.rs to compare glibc with mimalloc on their own workloads. The static musl benchmark leaves that choice open. The earlier public dependency-dense fixture favored mimalloc. Original allocator benchmarks

Make mimalloc an optional Cargo dependency with a default-enabled feature of the same name. Ordinary Cargo and Bazel builds continue to use mimalloc, including the static musl release. Omitting the feature selects Rust’s system allocator on the target platform.

Cargo users can pass --no-default-features --features vendored-protoc to retain the other default feature. The repository’s Bazel binary reads Cargo’s resolved features and accepts --features=-mimalloc to remove just the allocator feature. A consumer with its own rust_binary declaration can omit mimalloc from that target’s crate_features.

The GNU/Linux default binary’s vector growth calls mi_malloc_aligned. The binary built with --features=-mimalloc calls glibc’s malloc and posix_memalign. The static musl default still links mimalloc.

On arm64 macOS, both settings produced identical hash and edge files from the 26,448,878-byte public fixture. The 192 Rust tests, 21 CLI tests and format check passed with each setting. Fixture and reproduction script

Reproduce the GNU/Linux builds

out=$(mktemp -d)
flags=(-c opt --strip=never --@rules_rust//rust/settings:lto=thin
       --platforms=@rules_rs//rs/platforms:x86_64-unknown-linux-gnu)
bazel build "${flags[@]}" //:bazel-diff
cp bazel-bin/src/bazel-diff "$out/default"
bazel build "${flags[@]}" --features=-mimalloc //:bazel-diff
cp bazel-bin/src/bazel-diff "$out/system"

On a GNU/Linux host, run python3 reproduce.py "$out/default" "$out/system" using the published fixture scripts from #577.

Codex for Tamir.