diff options
| -rw-r--r-- | compiler/rustc_codegen_llvm/src/back/write.rs | 2 | ||||
| -rw-r--r-- | src/doc/rustc/src/instrument-coverage.md | 40 |
2 files changed, 25 insertions, 17 deletions
diff --git a/compiler/rustc_codegen_llvm/src/back/write.rs b/compiler/rustc_codegen_llvm/src/back/write.rs index 879baaa8556..0913715b3c0 100644 --- a/compiler/rustc_codegen_llvm/src/back/write.rs +++ b/compiler/rustc_codegen_llvm/src/back/write.rs @@ -425,7 +425,7 @@ fn get_pgo_sample_use_path(config: &ModuleConfig) -> Option<CString> { fn get_instr_profile_output_path(config: &ModuleConfig) -> Option<CString> { if config.instrument_coverage { - Some(CString::new(format!("{}", PathBuf::from("default_%m_%p.profraw").display())).unwrap()) + Some(CString::new("default_%m_%p.profraw").unwrap()) } else { None } diff --git a/src/doc/rustc/src/instrument-coverage.md b/src/doc/rustc/src/instrument-coverage.md index 0ae9e53af3c..e1340c893f9 100644 --- a/src/doc/rustc/src/instrument-coverage.md +++ b/src/doc/rustc/src/instrument-coverage.md @@ -97,7 +97,24 @@ $ echo "{some: 'thing'}" | target/debug/examples/formatjson5 - } ``` -After running this program, a new file, `default.profraw`, should be in the current working directory. It's often preferable to set a specific file name or path. You can change the output file using the environment variable `LLVM_PROFILE_FILE`: +After running this program, a new file, `default_%m_%p.profraw`, should be in the current working directory. This file takes advantage ofLLVM's support for rewriting special pattern strings to ensure `.profraw` files generated are unique. The following special pattern strings are rewritten as: + +- `%p` - The process ID. +- `%h` - The hostname of the machine running the program. +- `%t` - The value of the TMPDIR environment variable. +- `%Nm` - the instrumented binary’s signature: The runtime creates a pool of N raw profiles, used for on-line profile merging. The runtime takes care of selecting a raw profile from the pool, locking it, and updating it before the program exits. `N` must be between `1` and `9`, and defaults to `1` if omitted (with simply `%m`). +- `%c` - Does not add anything to the filename, but enables a mode (on some platforms, including Darwin) in which profile counter updates are continuously synced to a file. This means that if the instrumented program crashes, or is killed by a signal, perfect coverage information can still be recovered. + +```shell +$ echo "{some: 'thing'}" | target/debug/examples/formatjson5 - +... +$ ls default_11699812450447639123_0_20944.profraw +default_11699812450447639123_0_20944.profraw +``` + +In the example above, the value `11699812450447639123_0` in the generated filename is the instrumented binary's signature, which replaced the `%m` pattern and the value `20944` is the process ID of the binary being executed. + +You can also set a specific file name or path for the generated `.profraw` files by using the environment variable `LLVM_PROFILE_FILE`: ```shell $ echo "{some: 'thing'}" \ @@ -107,14 +124,6 @@ $ ls formatjson5.profraw formatjson5.profraw ``` -If `LLVM_PROFILE_FILE` contains a path to a non-existent directory, the missing directory structure will be created. Additionally, the following special pattern strings are rewritten: - -- `%p` - The process ID. -- `%h` - The hostname of the machine running the program. -- `%t` - The value of the TMPDIR environment variable. -- `%Nm` - the instrumented binary’s signature: The runtime creates a pool of N raw profiles, used for on-line profile merging. The runtime takes care of selecting a raw profile from the pool, locking it, and updating it before the program exits. `N` must be between `1` and `9`, and defaults to `1` if omitted (with simply `%m`). -- `%c` - Does not add anything to the filename, but enables a mode (on some platforms, including Darwin) in which profile counter updates are continuously synced to a file. This means that if the instrumented program crashes, or is killed by a signal, perfect coverage information can still be recovered. - ## Installing LLVM coverage tools LLVM's supplies two tools—`llvm-profdata` and `llvm-cov`—that process coverage data and generate reports. There are several ways to find and/or install these tools, but note that the coverage mapping data generated by the Rust compiler requires LLVM version 12 or higher, and processing the *raw* data may require exactly the LLVM version used by the compiler. (`llvm-cov --version` typically shows the tool's LLVM version number, and `rustc --verbose --version` shows the version of LLVM used by the Rust compiler.) @@ -181,11 +190,12 @@ A typical use case for coverage analysis is test coverage. Rust's source-based c The following example (using the [`json5format`] crate, for demonstration purposes) show how to generate and analyze coverage results for all tests in a crate. -Since `cargo test` both builds and runs the tests, we set both the additional `RUSTFLAGS`, to add the `-C instrument-coverage` flag, and `LLVM_PROFILE_FILE`, to set a custom filename for the raw profiling data generated during the test runs. Since there may be more than one test binary, apply `%m` in the filename pattern. This generates unique names for each test binary. (Otherwise, each executed test binary would overwrite the coverage results from the previous binary.) +Since `cargo test` both builds and runs the tests, we set the additional `RUSTFLAGS`, to add the `-C instrument-coverage` flag. If setting `LLVM_PROFILE_FILE` to specify a custom filename for the raw profiling data generated during the test runs, +apply `%m` in the filename pattern since there may be more than one test binary. This generates unique names for each test binary which is not done by default when setting the `LLVM_PROFILE_FILE` environment variable. +(Otherwise, each executed test binary would overwrite the coverage results from the previous binary.) If not setting `LLVM_PROFILE_FILE`, the `%m` and `%p` filename patterns are added by default. ```shell $ RUSTFLAGS="-C instrument-coverage" \ - LLVM_PROFILE_FILE="json5format-%m.profraw" \ cargo test --tests ``` @@ -210,7 +220,7 @@ test result: ok. 31 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out You should have one or more `.profraw` files now, one for each test binary. Run the `profdata` tool to merge them: ```shell -$ llvm-profdata merge -sparse json5format-*.profraw -o json5format.profdata +$ llvm-profdata merge -sparse default_*.profraw -o json5format.profdata ``` Then run the `cov` tool, with the `profdata` file and all test binaries: @@ -271,9 +281,8 @@ To include doc tests in the coverage results, drop the `--tests` flag, and apply ```bash $ RUSTFLAGS="-C instrument-coverage" \ RUSTDOCFLAGS="-C instrument-coverage -Z unstable-options --persist-doctests target/debug/doctestbins" \ - LLVM_PROFILE_FILE="json5format-%m.profraw" \ cargo test -$ llvm-profdata merge -sparse json5format-*.profraw -o json5format.profdata +$ llvm-profdata merge -sparse default_*.profraw -o json5format.profdata ``` The `-Z unstable-options --persist-doctests` flag is required, to save the test binaries @@ -302,8 +311,7 @@ $ llvm-cov report \ > version without doc tests, include: - The `cargo test ... --no-run` command is updated with the same environment variables - and flags used to _build_ the tests, _including_ the doc tests. (`LLVM_PROFILE_FILE` - is only used when _running_ the tests.) + and flags used to _build_ the tests, _including_ the doc tests. - The file glob pattern `target/debug/doctestbins/*/rust_out` adds the `rust_out` binaries generated for doc tests (note, however, that some `rust_out` files may not be executable binaries). |