# Be Code Style

> Fix BE (C++) code formatting issues using clang-format

- Skill: `apache/be-code-style` (Agent Skill)
- Install (CLI): `npx skillmds@latest add apache/be-code-style`
- Raw SKILL.md: https://api.skillmd.com/api/skills/apache/be-code-style/raw
- Safety review: pending
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: Coding & Dev Tools
- Author: apache (https://skillmd.com/u/apache)
- Updated: 2026-09-17
- Page: https://skillmd.com/skills/apache/be-code-style

---


## What I do

Fix C++ code formatting issues in the BE and Cloud modules using the project's clang-format configuration (v16).

## When to use me

- Before committing BE/Cloud C++ code changes
- When CI reports clang-format failures
- When you need to check or fix C++ code style

## Prerequisites

You need to confirm that the major version of the called clang-format is 16. If the current environment's default does not meet this requirement, try the following:

1. If `.vscode/settings.json` exists, use the clang-format.executable item in it.
2. If it is a worktree directory, use the `.vscode/settings.json` from the main directory.
3. Check the path to the compiler toolchain by trying to find it from the `PATH` environment variable, the current directory, and the main directory's `custom_env.sh`. Look for a clang-format with the major version number 16 in that path and its parent directory.

## Procedure

### Step 1: Auto-fix formatting

Run the project's formatting script, which enforces clang-format v16:

```bash
build-support/clang-format.sh
```

This formats all C++ files under `be/src`, `be/test`, `cloud/src`, `cloud/test` in-place, respecting `.clang-format` and `.clang-format-ignore`.

**Important**: Always use this script instead of invoking `clang-format` directly. The script checks that clang-format version 16 is installed and exits with an error if the wrong version is found. Using a different version will produce inconsistent formatting.

### Step 2: Check-only (no modification)

To verify formatting without modifying files:

```bash
build-support/check-format.sh
```

This outputs a diff of any formatting violations and exits non-zero if there are any.

### Step 3: Review and commit

After running `clang-format.sh`, review the changes with `git diff` to verify only formatting was changed, then stage and commit.

## Key Configuration

| File | Purpose |
|------|---------|
| `.clang-format` | Main formatting rules (Google-based, 100 col, 4-space indent) |
| `.clang-format-ignore` | Files excluded from formatting (third-party, generated) |
| `build-support/run_clang_format.py` | Python wrapper for parallel execution |

## Excluded Directories

The following are excluded from formatting (see `.clang-format-ignore`):

- `be/src/apache-orc/*`, `be/src/clucene/*`, `be/src/gutil/*`
- `be/src/glibc-compatibility/*`
- Specific third-party vendored files (mustache, sse2neon, utf8_check)
- `cloud/src/common/defer.h`

## Troubleshooting

| Problem | Solution |
|---------|----------|
| `clang-format not found` | Install clang-format v16 or set `CLANG_FORMAT_BINARY` env var |
| `version is not 16` | Install clang-format v16; on macOS: `brew install llvm@16` |
| Files not being formatted | Check `.clang-format-ignore` for exclusions |