Where is ssize_t defined in linux?

Question

OS: Debian 9 (Linux 4.9)

Compiler: GCC 8.2

Currently I am including (where size_t is defined) and

Answer 1

ssize_t is defined in sys/types.h.

Per the POSIX documentation:

NAME

sys/types.h - data types

SYNOPSIS

#include 

DESCRIPTION

The header shall define at least the following types:

...

ssize_t

    Used for a count of bytes or an error indication.