c - Type 'ssize_t' could not be resolved eclipse cdt -

I'm learning to write a simple driver for Linux (I have installed LibTu). But I have a problem my IDE Eclipse CDT can not see some kind of. the type 'ssize_t' can not be resolved but I am involved in it and add the path to the project, and I have enabled the index why eclipse sees some kind of cdT cantonment language?

clear-> project-> build- then build the main reason why eclipse focuses on me keeps.