Our current documentation style is to put the failure/example sections under their own header, like:

```
# Failure

...

# Example

...
```

Additionally, can you inline the failure modes from `getcwd` to here? Invoking the libc function is mostly just an implementation detail of this function, and we should try to document these functions as much as possible where they are.

Finally, you may want to make sure that this patch runs past `make check`, because the example here doesn't look like it's going to pass the tests. You also may want to consider adding more code to the example because just calling the function isn't very descriptive of how the function works or what you can do with the return value.