# Libfuzzer Integration Reference

## fuzzer_test GN Template

Use `fuzzer_test` to define libfuzzer targets:

```
fuzzer_test("my_fuzzer") {
  ...
}
```

Following arguments are supported:

| Argument | Description |
|----------|-------------|
| sources | **required** list of fuzzer test source files. |
| deps | fuzzer dependencies |
| additional_configs | additional GN configurations to be used for compilation |
| dict | a dictionary file for the fuzzer |
| libfuzzer_options | runtime options file for the fuzzer. See [Fuzzer Runtime Options](Fuzzer-Options) |


## Fuzzer Runtime Options

There are many different runtime options supported by libfuzzer. Options
are passed as command line arguments:

```
./fuzzer [-flag1=val1 [-flag2=val2 ...] ] [dir1 [dir2 ...] ]
```

Most common flags are:

| Flag | Description |
|------|-------------|
| max_len | Maximum length of test input. |
| timeout | Timeout of seconds. Units slower than this value will be reported as bugs. |

A fuller list of options can be found at [Libfuzzer Usage] page and by running
the binary with `-help=1`.

To specify these options for Clusterfuzz, create `<my_fuzzer>.options` file:

```
[libfuzzer]
max_len=500
```

and specify the file in `libfuzzer_options` target attribute.

[Libfuzzer Usage]: http://llvm.org/docs/LibFuzzer.html#usage