[Bug c/127127] Provide built-in macro __SSIZE_TYPE__ for ssize_t

[rguenth at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=127127

--- Comment #1 from Richard Biener <rguenth at gcc dot gnu.org> ---
I think

typedef signed __SIZE_TYPE__ ssize_t;

works?