OpenSTA/.cursor/rules/cpp-coding-standards.mdc

---
description: C++ coding standards and formatting for OpenSTA
globs: ["**/*.cc", "**/*.hh", "**/*.h"]
alwaysApply: true
---

# C++ Coding Standards

## File-internal helpers (translation-unit local)

- For helpers used only in one `.cc` file, put them in the **same namespace** as the rest of the implementation (e.g. `namespace sta { ... }`).
- Mark them **`static`** at namespace scope so they have internal linkage.
- **Do not** wrap them in an **anonymous namespace** in this project (no `namespace { ... }` file-static helpers). The user preference is `static` inside the real namespace, not a nested anonymous namespace inside `sta` or at file scope before `sta`.

## Line Width

- **Keep lines under 90 characters** to match `.clang-format` (ColumnLimit: 90).
- Only break a line when it would exceed 90 characters. Do not introduce unnecessary line breaks when the expression fits on one line.
- When a break is needed, break at logical points: after commas, before operators. Keep the first argument on the same line as the opening paren (do not break immediately after an opening paren).

## Naming Conventions

- **Classes**: Upper camel case (`ClassName`)
- **Member functions**: Lower camel case (`memberFunction`)
- **Member variables**: Snake case with trailing underscore (`member_variable_`)
- **Functions**: Lower camel case (`functionName`)
- **Variables**: Snake case

## Code Style

- Use `#pragma once` for header guards.
- Return type on the line before the function name; arguments on separate lines when long.
- No braces for single-line if/for; use braces for multi-line bodies.
- Prefer `std::string` over `char*` for string members.
- Prefer pass-by-value and move for sink parameters (parameters that get stored).

## File Extensions

- C++ source: `.cc`
- C++ headers: `.hh`

## Include order

Sort `#include` lines **lexicographically by the path inside** `<>`
or `""` (case-sensitive). Separate **groups** with a single blank line.

### Translation units (`*.cc`)

1. **Primary header(s)** for this file only:
   - `#include "Stem.hh"` where `Stem` matches the basename of the `.cc` file (e.g. `Foo.cc` → `Foo.hh`).
   - If the file uses a paired private header, include `#include "StemPvt.hh"` **immediately after** `Stem.hh` (e.g. `MakeTimingModel.cc` → `MakeTimingModel.hh` then `MakeTimingModelPvt.hh`).
   - Do **not** pull in other headers just because their names share a prefix with `Stem` (e.g. `SearchClass.hh` is not a “primary” include for `Search.cc`; it belongs in the project group below).

2. **System / standard library** headers: `#include <...>` lines, sorted alphabetically.

3. **All other project** headers: `#include "..."` lines, sorted alphabetically (including `search/Crpr.hh`-style paths and includes from `liberty/`, etc.).

If a **comment or special block** intentionally splits the include list (e.g. a third-party note before `#include "cudd.h"`), keep that structure; sort only within each contiguous run of `#include` lines unless merging groups is clearly safe.

### Headers (`*.hh`)

After `#pragma once` (and the file’s license block, if present):

1. **System** `#include <...>` lines, sorted alphabetically.

2. **Project** `#include "..."` lines, sorted alphabetically.