Skip to content

Fix documentation example for gcov profiling #72615

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Merged
bors merged 2 commits into from
Jun 8, 2020
Merged

Fix documentation example for gcov profiling #72615

Changes from 1 commit
Commits
Show all changes
2 commits
Select commit Hold shift + click to select a range
2b26b8b
Fix documentation example for gcov profiling
jschwe May 26, 2020
7bf026e
Doc: unstable book - profile.md: improve wording
jschwe Jun 3, 2020
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
7 changes: 6 additions & 1 deletion src/doc/unstable-book/src/compiler-flags/profile.md
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -12,10 +12,15 @@ For example:
```Bash
cargo new testgcov --bin
cd testgcov
export RUSTFLAGS="-Zprofile"
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` apply to everything that cargo builds and runs during a build, including build scripts!
To avoid this, pass a `RUSTC_WRAPPER` program to cargo that only adds the profiling flags to rustc for the specific
crates you want to profile.
Copy link
Contributor

@tmiasko tmiasko Jun 2, 2020

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

When --target flag is passed to cargo, the RUSTFLAGS no longer apply to build scripts and procedural macros. This could be more convenient to use than a wrapper.

Copy link
Contributor Author

@jschwe jschwe Jun 3, 2020

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

Thanks for the feedback. I added a sentence regarding --target and mentioned RUSTC_WRAPPER as an option if one wants more control over which crates get instrumented.