cpp-style

name	cpp-style
description	C++ naming, formatting, static analysis, and RTTI rules for LuisaCompute.

Naming

• Classes / structs / enums: CamelCase (MyClass, RenderPipeline)
• Functions & public vars: snake_case (get_value, process_data)
• Private/protected members & functions: _snake_case (_private_var, _internal_helper())
• Constants: kCamelCase or UPPER_SNAKE_CASE for macros
• Template params: CamelCase
• Namespaces: luisa, luisa::compute, vstd, etc. Keep compact.

Syntax Check

Use the project C++ syntax checker:

python scripts/check_cpp_syntax.py <file>.cpp

It runs clangd with the project's compile_commands.json and .clang-tidy. Skip files not in compile_commands.json.

Formatting

Format with the project .clang-format (bundled in this skill; the project root copy is authoritative).

Base: LLVM style. Key overrides:

• Indent: 4 spaces, no tabs. Continuation indent 4. Case labels indented. Preprocessor indent 2.
• Braces: K&R (attach). No break before braces. Indent braces off.
• Line width: unlimited (ColumnLimit: 0).
• Pointers/refs: right-aligned (int *p, int &r).
• Access modifiers: indent offset -4 (flush with class). Empty lines before/after left as-is.
• Short constructs: allow single-line for short blocks, functions, ifs, loops, lambdas, enums, case labels.
• Constructor init: not forced one-per-line; no break before comma.
• Templates / concepts: break declarations only when multiline; indent requires clause.
• Spaces: before =, ctor-initializer :, inheritance :, range-for :. No space after C-style casts, !, template keyword, before braced lists. No space in empty parens or before trailing comments.
• Alignment: after open brackets & operands; don't align consecutive assignments.
• Includes/using: never auto-sort.
• Namespaces: compact single-line when short; no indentation inside (ShortNamespaceLines: 0).
• Strings/comments: break string literals; don't reflow comments.
• Macros: control-flow-like ($if, $elif, $else, $for, $while, $loop, $switch, $case, $default) get space before (. Function-like macros don't. Special lists:
  • ForEachMacros: LUISA_STRUCT, LUISA_BINDING_GROUP, LUISA_BINDING_GROUP_TEMPLATE
  • IfMacros: $if, $elif, $else, $for, $while, $loop, $switch, $case, $default
  • StatementMacros: LUISA_MAP

Static Analysis

Run .clang-tidy (bundled in this skill; the project root copy is authoritative).

All checks disabled (-*), then enabled by category:

• bugprone-*
• cert-*
• cppcoreguidelines-*
• google-* (default-arguments, explicit-constructor, runtime-operator)
• hicpp-*
• misc-*
• modernize-*
• mpi-, openmp-
• performance-*
• portability-*
• readability-*

See the bundled .clang-tidy for the exact check list.

No RTTI

RTTI is disabled for project code. Do not use:

• dynamic_cast — use static_cast when type is known
• typeid
• std::type_info

Prefer virtual dispatch or explicit type tags for type-safe downcasting. Third-party code under src/ext is exempt.

Integer Types

Prefer fixed-width integer types:

• Use: int32_t, uint32_t, int64_t, uint64_t, int16_t, uint16_t, int8_t, uint8_t
• size_t is acceptable for sizes/indices per STL convention.
• Prefer std::byte for raw byte data.
• Avoid unsigned int, long long, unsigned long, short, and char for arithmetic. Some platform/system headers may define aliases such as uint; avoid introducing new uses in project code.

Verification

After editing C++ files:

# Check syntax / tidy diagnostics
python scripts/check_cpp_syntax.py src/foo.cpp

# Check formatting (dry run; replace --dry-run with -i to apply)
clang-format --dry-run --Werror src/foo.cpp

# Run clang-tidy on a specific file
clang-tidy -p build src/foo.cpp

When changing build-affecting files, configure and build a relevant target:

xmake f -m debug -c
xmake build <target>

Resources

• .clang-format — bundled copy of the project formatter config.
• .clang-tidy — bundled copy of the project static-analysis config.
• .clangd — project root configuration for clangd diagnostics (not bundled; see project root).