> ## Documentation Index
> Fetch the complete documentation index at: https://differens.ossl.dev/llms.txt
> Use this file to discover all available pages before exploring further.

# C

> Semantic diffing for C

## C extractor

The C extractor maps tree-sitter C CST nodes to canonical concepts. C has no `name` fields in its grammar, so every declaration name is recovered through the declarator chain: `function_definition` → `function_declarator` → identifier.

### Detected concepts

| tree-sitter node type | Canonical concept |
| - | - |
| `function_definition` | Function |
| `declaration` / `init_declarator` | Variable |
| `field_declaration` | Variable |
| `struct_specifier` | Struct |
| `enum_specifier` | Enum |
| `parameter_declaration` | Parameter |
| `preproc_include` | PreprocInclude |
| `return_statement` | Return |
| `if_statement` | IfBlock |
| `number_literal` | number\_literal |

### Example

Renaming a function:

```c theme={null}
// old.c
int total(int a, int b) { return a + b; }
```

```c theme={null}
// new.c
int sum(int a, int b) { return a + b; }
```

Running `differens old.c new.c`:

```
~ renamed function `total` to `sum`
```

### Known limitations

* Preprocessor macros are tokens, not structure: a macro that generates code does not expand before diffing.
* Function prototypes and definitions are matched structurally; a prototype moving between headers reports as a move, not a signature change.