Unfamiliar notation in manpage mmap(2): void addr[.length]

Question

What does the notation void addr[.length] in mmap(2) mean? I could interpret void *addr or size_t length, but what is the semantics of this "mixed" notation?

Answer 1

Google solved this for me after all: void addr[.length] is a common reference to alternative ways for passing an array:

int foo(void *addr);
int foo(void addr[]);
int foo(void addr[10]);