`st_size` is [defined](http://pubs.opengroup.org/onlinepubs/9699919799/basedefs/sys_stat.h.html) as being an `off_t`.

`off_t` is [defined](http://pubs.opengroup.org/onlinepubs/9699919799/basedefs/sys_types.h.html) as being a **signed integer type**.

Why is `st_size` defined as a signed type? Can it be negative? What does it mean if it is negative?