????????????????????????????????? C ??????????????????????????????

???????????????????????????????????????????????????????????????????????????uid_t ????????? gid_t ??????????????????????????????????????????????????????????????????????????????

???????????????????????????????????????????????????????????????????????????

1 #include <unistd.h>
2 #include <stdlib.h>
3 #include <stdio.h>
4
5 int
6 main(void)
7 {
8 uid_t negone = -1;
9
10 if (getuid() < 0)
11 exit(1);
12
13 (void) setreuid(negone, getuid());
14
15 (void) printf("%ld\n", getuid());
16
17 return (0);
18 }

• Sun ??? Studio 11 ????????????????????????????????????????????????????????????

  "uid.c", line 8: warning: initializer does not fit or is out of range: -1"

• Studio 11 ??? lint ?????????????????????????????????????????????

  ((8) warning: constant truncated by assignment

  (8) warning: initializer will be sign-extended: -1

  (10) warning: suspicious comparison of unsigned with 0: op "<"

  function argument ( number ) type inconsistent with format

• gcc -Wall -Wextra ?????????????????????????????????????????????

  uid.c:10: warning: comparison of unsigned expression < 0 is always false

  uid.c:15: warning: long int format, uid_t arg (arg 2)

?????????????????????????????? C ???????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????