clang-tidy-check

## What I do Run clang-tidy static analysis on newly added or modified C++ files in the BE and Cloud modules, using the project's `.clang-tidy` configuration. The script parses `git diff` to identify changed line ranges and filters clang-tidy output to diagnostics on those lines where possible, reducing noise from pre-existing code. Diagnostics from included headers that were not part of the diff are filtered out, though some edge cases may still appear. ## When to use me - After building BE, before committing C++ code changes - When CI reports clang-tidy warnings on your PR - When you want to proactively check new code for common bugs and style issues ## Prerequisites 1. **The relevant module must be built first** — clang-tidy needs `compile_commands.json` generated during the CMake build. For BE files, build BE; for Cloud files, build Cloud. 2. **clang-tidy must be installed** — the project uses clang-tidy from the LDB toolchain. ## Procedure ### Step 1: Build the relevant module (if not already done) For **BE** files: ```bash ./build.sh --be -j${DORIS_PARALLELISM} ``` This generates `compile_commands.json` in `be/build_Release/` or `be/build_ASAN/`. For **Cloud** files: ```bash ./build.sh --cloud -j${DORIS_PARALLELISM} ``` This generates `compile_commands.json` in `cloud/build_Release/` or `cloud/build_ASAN/`. **Note**: A single compilation database typically covers only one module (BE or Cloud). If your changes span both modules, you may need to run clang-tidy twice with different `--build-dir` values. ### Step 2: Run clang-tidy on changed files ```bash build-support/run-clang-tidy.sh ``` By default, this script: - Detects changed C++ files via `git diff` (uncommitted changes + staged changes) - Automatically finds `compile_commands.json` from the latest BE build - Runs clang-tidy using the `.clang-tidy` config - Skips files in excluded directories (third-party, generated code) - Reports warnings grouped by file **Options:** ```bash # Compare against a specific branch (e.g., for PR review) build-support/run-clang-tidy.sh --base origin/master # Check specific files (all lines, no line-level filtering) build-support/run-clang-tidy.sh --files be/src/vec/functions/my_new_func.cpp # Report ALL warnings in changed files (no line filtering) build-support/run-clang-tidy.sh --full # Specify build directory explicitly (required for Cloud if BE build dir was auto-detected) build-support/run-clang-tidy.sh --build-dir be/build_ASAN # Check Cloud files with Cloud compilation database build-support/run-clang-tidy.sh --build-dir cloud/build_ASAN # Apply auto-fixes where possible (note: fixes may apply beyond changed lines) build-support/run-clang-tidy.sh --fix ``` **Important**: By default, only warnings on changed lines are reported (diagnostics from headers not in the diff are filtered out). This prevents the agent from "fixing" unrelated pre-existing warnings in large files. Use `--full` to see all warnings if needed. ### Step 3: Interpret and fix warnings clang-tidy output looks like: ``` be/src/vec/functions/foo.cpp:42:5: warning: use auto when initializing with a cast [modernize-use-auto] be/src/vec/functions/foo.cpp:55:1: warning: function 'process' exceeds recommended size [readability-function-size] ``` **Fix approach:** 1. Fix all warnings that represent real issues (bugs, performance, readability) 2. For false positives or intentional patterns, add `// NOLINT(check-name)` with a brief justification 3. Report any warnings you cannot reasonably fix ### Step 4: Verify Re-run the script to confirm all warnings are resolved: ```bash build-support/run-clang-tidy.sh ``` ## Enabled Checks (from `.clang-tidy`) | Category | Examples | |----------|----------| | `clang-diagnostic-*` | Compiler diagnostics | | `clang-analyzer-*` | Static analysis (null deref, use-after-free, etc.) | | `bugprone-*` | Use-after-move, redundant branch condition, unused RAII | | `modernize-*` | Auto, range-for, nullptr (excludes trailing return, nodiscard) | | `readability-*` | Function size (≤80 lines), cognitive complexity (≤50) | | `performance-*` | String find, inefficient algorithm, move-const-arg | | `misc-redundant-expression` | Redundant expressions | ## Excluded Directories Files in these paths are automatically skipped: - `be/src/apache-orc/`, `be/src/clucene/`, `be/src/gutil/` - `be/src/glibc-compatibility/` - `contrib/` (all third-party code) - Generated code directories ## NOLINT Usage When a clang-tidy warning cannot be fixed, suppress it with a comment: ```cpp // Good: specific check name + reason int x = (int)y; // NOLINT(modernize-use-auto): explicit cast for clarity // Bad: blanket suppression without reason int x = (int)y; // NOLINT ``` ## Troubleshooting | Problem | Solution | |---------|----------| | `compile_commands.json not found` | Build BE first: `./build.sh --be -j${DORIS_PARALLELISM}` | | `clang-tidy not found` | Install via LDB toolchain or `apt install clang-tidy-16` | | Too many warnings on old code | Use `--base` to diff against a branch, ensuring only your changes are checked | | Warning in header included by your file | Only fix if the header is also in your changeset; otherwise note it in your report |