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# libFuzzer Integration Reference
## Supported Platforms and Configurations
### Linux
Linux is fully supported by libFuzzer and ClusterFuzz with following sanitizer
configurations:
| GN Argument | Description |
|--------------|----|
| is_asan=true | enables [Address Sanitizer] to catch problems like buffer overruns. |
| is_msan=true | enables [Memory Sanitizer] to catch problems like uninitialed reads. |
| is_ubsan_security=true | enables [Undefined Behavior Sanitizer] to catch<sup>\[[1](#Notes)\]</sup> undefined behavior like integer overflow. |
Configuration example:
```bash
# With address sanitizer
gn gen out/libfuzzer '--args=use_libfuzzer=true is_asan=true enable_nacl=false' --check
```
### Mac
Mac is experimentally supported by libFuzzer with `is_asan` configuration. Mac
support is not provided by ClusterFuzz.
Configuration example:
```bash
gn gen out/libfuzzer '--args=use_libfuzzer=true is_asan=true enable_nacl=false mac_deployment_target="10.7"' --check
```
## 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, list all parameters in
`libfuzzer_options` target attribute:
```
fuzzer_test("my_fuzzer") {
...
libfuzzer_options = [
"max_len=2048",
"use_traces=1",
]
}
```
[libFuzzer Usage]: http://llvm.org/docs/LibFuzzer.html#usage
[Address Sanitizer]: http://clang.llvm.org/docs/AddressSanitizer.html
[Memory Sanitizer]: http://clang.llvm.org/docs/MemorySanitizer.html
[Undefined Behavior Sanitizer]: http://clang.llvm.org/docs/UndefinedBehaviorSanitizer.html
|
