[rustc.git] / src / doc / unstable-book / src / compiler-flags / profile.md

# `profile`

The tracking issue for this feature is: [#42524](https://github.com/rust-lang/rust/issues/42524).

------------------------

This feature allows the generation of code coverage reports.

Set the `-Zprofile` compiler flag in order to enable gcov profiling.

For example:
```Bash
cargo new testgcov --bin
cd testgcov
export RUSTFLAGS="-Zprofile -Ccodegen-units=1 -Copt-level=0 -Clink-dead-code -Coverflow-checks=off -Zpanic_abort_tests -Cpanic=abort"
export CARGO_INCREMENTAL=0
cargo build
cargo run
```

Once you've built and run your program, files with the `gcno` (after build) and `gcda` (after execution) extensions will be created.
You can parse them with [llvm-cov gcov](https://llvm.org/docs/CommandGuide/llvm-cov.html#llvm-cov-gcov) or [grcov](https://github.com/mozilla/grcov).

Please note that `RUSTFLAGS` by default applies to everything that cargo builds and runs during a build!
When the `--target` flag is explicitly passed to cargo, the `RUSTFLAGS` no longer apply to build scripts and procedural macros.
For more fine-grained control consider passing a `RUSTC_WRAPPER` program to cargo that only adds the profiling flags to
rustc for the specific crates you want to profile.
Commit	Line	Data
041b39d2 XL	1	# `profile`
	2
	3	The tracking issue for this feature is: [#42524](https://github.com/rust-lang/rust/issues/42524).
	4
	5	------------------------
	6
	7	This feature allows the generation of code coverage reports.
	8
	9	Set the `-Zprofile` compiler flag in order to enable gcov profiling.
	10
	11	For example:
	12	```Bash
	13	cargo new testgcov --bin
	14	cd testgcov
f035d41b XL	15	export RUSTFLAGS="-Zprofile -Ccodegen-units=1 -Copt-level=0 -Clink-dead-code -Coverflow-checks=off -Zpanic_abort_tests -Cpanic=abort"
f035d41b XL	16	export CARGO_INCREMENTAL=0
041b39d2 XL	17	cargo build
	18	cargo run
	19	```
	20
	21	Once you've built and run your program, files with the `gcno` (after build) and `gcda` (after execution) extensions will be created.
0bf4aa26	22	You can parse them with [llvm-cov gcov](https://llvm.org/docs/CommandGuide/llvm-cov.html#llvm-cov-gcov) or [grcov](https://github.com/mozilla/grcov).
f035d41b XL	23
f035d41b XL	24	Please note that `RUSTFLAGS` by default applies to everything that cargo builds and runs during a build!
6a06907d XL	25	When the `--target` flag is explicitly passed to cargo, the `RUSTFLAGS` no longer apply to build scripts and procedural macros.
6a06907d XL	26	For more fine-grained control consider passing a `RUSTC_WRAPPER` program to cargo that only adds the profiling flags to
f035d41b	27	rustc for the specific crates you want to profile.