glibc + uid ?

[V13]

Mporei na moy eksigisei kapoios an ayto einai sfalma ths glibc h kapoioy 
alloy?

Sto /usr/include/bits/types.h exei:

typedef __u_int __uid_t;                /* Type of user identifications.  */
typedef __u_int __gid_t;                /* Type of group identifications.  */

Eno sto man ths chown(2) leei kathara:

int chown(const char *path, uid_t owner, gid_t group);

       If  the owner or group is specified as -1, then that ID is
       not changed.

To opoio kai doylevei alla me tin katallili xorodia:

hell:/tmp$ cat a.cc 
#include "sys/types.h"
#include "unistd.h"

int main()
{
        chown ("/dev/null",-1,-1);
}

hell:/tmp$ g++ a.cc     
a.cc: In function `int main()':
a.cc:6: warning: passing negative value `-1' for argument passing 2 of `int 
   chown(const char*, unsigned int, unsigned int)'
a.cc:6: warning: argument of negative value `-1' to `unsigned int'
a.cc:6: warning: passing negative value `-1' for argument passing 3 of `int 
   chown(const char*, unsigned int, unsigned int)'
a.cc:6: warning: argument of negative value `-1' to `unsigned int'

sto opoio tygxanei na exei apolyto dikio o compiler...

ase poy les:

uid_t	u;
u=-1;
if (u<0) { exit(0); }

kai den doylevei, eno tha perimenes oti symfvna me to man ths chown(2) kati 
tetoio einai dynato.. kai edo soy petaei:

a.cc:9: warning: assignment of negative value `-1' to `uid_t'

WTF?

<<V13>>

p.s. kai to zori tis ypotheseis einai oti den mporeis na apalageis apo ayta ta 
warnings, ektos kai an katafygeis se alximies me signed kai unsigned.