Fix cargo bench.

Benchmarking is only supported by Rust nightly and therefore before this commit it was disabled by default and hidden behind `bench` feature. OTOH, declaring such feature in `Cargo.toml` would have broken `cargo +stable test --all-features`. Therefore the commit switches from using a `bench` *feature* to using a `bench` config. This commit also makes `use std:convert::TryInto` conditional via `#[cfg(debug_assertions)]`. This avoids the following build error: ``` $ RUSTFLAGS="--cfg=bench" cargo +nightly bench --all-features ... error: unused import: `std::convert::TryInto` --> src/cast.rs:1:5 | 1 | use std::convert::TryInto; | ^^^^^^^^^^^^^^^^^^^^^ ``` Additionally, this commit also opts into the `test` feature (only if the "bench" configurtaion is requested, because benchmarking is only available in the nightly version of the compiler) and declares the `extern crate test` dependency on the compiler-provided `test` crate. This avoids the following build errors: ``` $ RUSTFLAGS="--cfg=bench" cargo +nightly bench --all-features ... error[E0433]: failed to resolve: use of undeclared crate or module `test` --> src/optimize.rs:710:33 | 710 | fn bench_optimize(bencher: &mut test::Bencher) { | ^^^^ use of undeclared crate or module `test` ``` ``` $ RUSTFLAGS="--cfg=bench" cargo +nightly bench --all-features ... error[E0658]: use of unstable library feature "test" --> src/optimize.rs:710:33 | 710 | fn bench_optimize(bencher: &mut test::Bencher) { | ^^^^^^^^^^^^^ | = note: see issue #50297 <rust-lang/rust#50297> for more information = help: add `#![feature(test)]` to the crate attributes to enable ``` After these changes the following command line succeeds: ``` $ RUSTFLAGS="--cfg=bench" cargo +nightly bench --all-features ... test bits::bench_find_min_version ... bench: 1 ns/iter (+/- 0) test bits::bench_push_splitted_bytes ... bench: 3,862 ns/iter (+/- 58) test optimize::bench_optimize ... bench: 19 ns/iter (+/- 0) ```
anforowicz · Apr 28, 2023 · c037ab9 · c037ab9
1 parent 3bb1dd7
commit c037ab9
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Showing 4 changed files with 13 additions and 3 deletions.
diff --git a/src/bits.rs b/src/bits.rs
@@ -153,7 +153,7 @@ fn test_push_number() {
     );
 }
 
-#[cfg(feature = "bench")]
+#[cfg(bench)]
 #[bench]
 fn bench_push_splitted_bytes(bencher: &mut test::Bencher) {
     bencher.iter(|| {
@@ -1084,7 +1084,7 @@ mod encode_auto_tests {
     }
 }
 
-#[cfg(feature = "bench")]
+#[cfg(bench)]
 #[bench]
 fn bench_find_min_version(bencher: &mut test::Bencher) {
     use test::black_box;

diff --git a/src/cast.rs b/src/cast.rs
@@ -1,3 +1,4 @@
+#[cfg(debug_assertions)]
 use std::convert::TryInto;
 
 // TODO remove this, use try_into wher as_* is used

diff --git a/src/lib.rs b/src/lib.rs
@@ -14,10 +14,19 @@
 )]
 #![cfg_attr(feature = "bench", doc(include = "../README.md"))]
 // ^ make sure we can test our README.md.
+// TODO: Avoid using `feature = "bench"` above.
 #![cfg_attr(docsrs, feature(doc_cfg))]
 // No `unsafe` please.  If `unsafe` is really needed, then please
 // consider encapsulating it in a separate crates.io crate.
 #![forbid(unsafe_code)]
+// Using `#[bench]`, `test::Bencher`, and `cargo bench` requires opting into the unstable `test`
+// feature.  See https://github.com/rust-lang/rust/issues/50297 for more details.  Benchmarks
+// features are only available in the nightly versions of the Rust compiler - to keep stable
+// builds working we only enable benching behind the "bench" config.  To run the benchmarks
+// use: `RUSTFLAGS='--cfg=bench' cargo +nightly bench --all-features`
+#![cfg_attr(bench, feature(test))]
+#[cfg(bench)]
+extern crate test;
 
 // Re-exported dependencies.
 #[cfg(feature = "bmp")]

diff --git a/src/optimize.rs b/src/optimize.rs
@@ -705,7 +705,7 @@ mod optimize_tests {
     }
 }
 
-#[cfg(feature = "bench")]
+#[cfg(bench)]
 #[bench]
 fn bench_optimize(bencher: &mut test::Bencher) {
     use crate::types::Version;