The tracking issue for this feature is: #42524.

This feature allows the generation of code coverage reports.

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

For example:

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"
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 or 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.