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82 lines
2.6 KiB
Markdown
82 lines
2.6 KiB
Markdown
# Code coverage
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LLVM provides a set of tools to collect code coverage data and present the data
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in human-consumable forms.
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## Building a suitable binary
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The compiler flag to generate code coverage data has been stabilized since Rust
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1.60.
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An instrumented binary can be built with the following command:
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```shell
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cargo clean && RUSTFLAGS='-C instrument-coverage' cargo build
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```
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Using either `debug` or `release` profile is fine. You will need to adjust
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the path for some commands.
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## Running the binary
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Run the binary as you normally would. When the process exits, you will see
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files with the prefix `profraw`.
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Multiple runs of the same binary will produce multiple `profraw` files.
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The more diverse the runs are, the better. Try to exercise different features
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as much as possible.
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## Combining raw data
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Raw data files can be combined with `llvm-profdata`.
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```shell
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rustup component add llvm-tools-preview
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# Assuming profraw files reside in the current directory and its children directories
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find . -name '*.profraw' -exec llvm-profdata merge -sparse {} -o coverage.profdata \;
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```
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A file named `coverage.profdata` will be generated.
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## Generating HTML files for human consumption
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This can be done either with LLVM or `grcov`.
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Here is an example using grcov.
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```shell
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cargo install grcov
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# Assuming the profdata file is in the top level directory of the Cloud Hypervisor repository
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grcov . --binary-path ./target/x86_64-unknown-linux-gnu/release -s . -t html --branch --ignore-not-existing -o coverage-html-output/
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```
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You can then open the `index.html` file under coverage-html-output to see the
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results.
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## Notes on running the in-tree integration tests and unit tests
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Please set RUSTFLAGS the same way while invoking `dev_cli.sh`. The script will
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pass RUSTFLAGS to the container.
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Since the `profraw` files are generated from within the container, the file
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paths embedded in the data files are going to be different. It is easier to do
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the data processing from within the container if you don't want to fight the
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tool chain.
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```shell
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# Get a shell
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./scripts/dev_cli.sh shell
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# Install llvm-tools-preview for llvm-profdata
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rustup component add llvm-tools-preview
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# Merge data files by using the following command
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find . -name '*.profraw' -exec `rustc --print sysroot`/lib/rustlib/x86_64-unknown-linux-gnu/bin/llvm-profdata merge -sparse {} -o coverage.profdata \;
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# As of writing, the container has Rust 1.67.1. It is too old for grcov.
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rustup install stable
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cargo +stable install grcov
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# Run grcov as usual
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grcov . --binary-path ./target/x86_64-unknown-linux-gnu/release -s . -t html --branch --ignore-not-existing -o coverage-html-output/
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```
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