The POSIX C type
is available on Unix-like systems in
Windows Visual Studio
However, ssize_t is POSIX, but not C standard.
It’s possible to define a signed size type “ssize_t” using “ptrdiff_t” for “ssize_t” in
size_t bit width is guaranteed by
standards to have bit width not less than 16.
ptrdiff_t bit width is guaranteed by
standard to have bit width not less than 16, and
standard to have bit width not less than 17.
shows how to use ssize_t across computing platforms.