meta: add clang-format

.clang-format

@@ -0,0 +1,33 @@
+---
+BasedOnStyle: LLVM
+Language: Cpp
+
+ColumnLimit: 100
+IndentWidth: 4
+TabWidth: 4
+UseTab: Always
+
+ContinuationIndentWidth: 4
+ConstructorInitializerIndentWidth: 4
+
+AlignAfterOpenBracket: BlockIndent
+
+# Put function names + args on their own lines
+AlwaysBreakAfterReturnType: All
+
+# Put all initializers onto their own lines.
+PackConstructorInitializers: CurrentLine
+
+# Put all function arguments on their own lines.
+BinPackArguments: false
+BinPackParameters: false
+
+# If control statements are wrapped to multiple lines, we want the { to be on the next line
+# to improve readability. Otherwise, it can happen that the line containing the { gets the same
+# indentation level as the control statement's body.
+BreakBeforeBraces: Custom
+BraceWrapping:
+    AfterControlStatement: MultiLine
+
+# Format braces as {1, 2, 3}, not as { 1, 2, 3 }.
+Cpp11BracedListStyle: true

.github/workflows/pre-commit.yml

@@ -0,0 +1,11 @@
+name: pre-commit
+
+on: [merge_group, pull_request]
+
+jobs:
+  pre-commit:
+    runs-on: ubuntu-latest
+    steps:
+    - uses: actions/checkout@v4
+    - uses: actions/setup-python@v3
+    - uses: pre-commit/[email protected]

.pre-commit-config.yaml

@@ -0,0 +1,14 @@
+fail_fast: false
+repos:
+  - repo: https://github.com/pocc/pre-commit-hooks
+    rev: 336fdd7c3cab698ead0b1c95157b9e74d3906b62
+    hooks:
+      - id: clang-format
+        additional_dependencies: [clang-format==19.1.3]
+        args: ["-i"]
+        exclude: >
+          (?x)^(
+            options/ansi/musl-generic-math/.*|
+            options/ansi/generic/complex/.*|
+            options/posix/musl-generic-regex/.*
+          )

README.md

@@ -49,6 +49,10 @@ The type of library to be built (static, shared, or both) is controlled by meson
 
 We also support building with `-Db_sanitize=undefined` to use UBSan inside mlibc. Note that this does not enable UBSan for external applications which link against `libc.so`, but it can be useful during development to detect internal bugs (e.g when adding new sysdeps).
 
+## Running pre-commit hooks
+
+To format your code before submitting a PR, you should install [`pre-commit`](https://pre-commit.com/). Then do `pre-commit install` to install the git hook which runs each time you commit. Alternatively, you can do `pre-commit run -a` to manually format all files.
+
 ## Running Tests
 
 The `mlibc` test suite can be run under a Linux host. To do this, first install a set of kernel headers (as described [here](https://docs.kernel.org/kbuild/headers_install.html)), then run from the project root: