when to size_t for representing length instead of int ?

[none <ytrezq@sdf-eu.org>]

Hello,

I wanted to known the rules in coding guidelines concerning the use of 
size_t.
It seems the signed int type is used most of the time for representing 
string sizes, including in some parts written by Linus in /lib.
They’re can buffer overflows attack if ssize_t if larger than 
sizeof(int) (though I agree this isn’t the only way, but at least it´s 
less error prone).

So is it guaranteed for all current and future cpu architectures the 
Linux kernel support that ssize_t will always be equal to sizeof(int) ?

regards,