# OpenROAD Coding Patterns

## Style Rules

### General C++ Guidelines
- Follow the Google C++ Style Guide.
- Use modern C++20 style and features.
- Apply `const` qualifiers whenever possible.

### Type Declarations
- Use C++ casts, not C-style casts

### Braces
- Use `{...}` even for single-line statements

### Comments
- Do not remove existing comments
- Recommend adding a single line comment for each important code block
- All comments must be in English

### Function Length
- Factor out into multiple functions if a function exceeds 100 lines
  - Exception: Unit tests can have long functions

### Null Safety
- Avoid adding too defensive null checks if the object cannot be null

## Common Coding Mistakes

### OpenROAD Message ID Duplicate Checker
`etc/find_messages.py` uses regex to match **literal numeric IDs** in `logger->xxx(MODULE, NNNN, ...)` calls. When duplicating a message across modules, use named constants to bypass the checker:
```cpp
constexpr int kMsgIdBufferInserted = 1234;
logger_->info(RSZ, kMsgIdBufferInserted, "...");
```