port to GNU hosts, where getuid and friends can fail

* src/groups.c (main):
* src/install.c (need_copy):
* src/su.c (log_su):
* src/test.c (unary_operator):
* src/whoami.c (main):
Don't assume that getuid and friends always succeed.
This fixes the same problem that we recently fixed with 'id'.

1 files changed, 12 insertions, 4 deletions

diff --git a/src/test.c b/src/test.c
index 362df65d8..1b06ca86e 100644
--- a/src/test.c
+++ b/src/test.c
@@ -414,13 +414,21 @@ unary_operator (void)
 
     case 'O':			/* File is owned by you? */
       unary_advance ();
-      return (stat (argv[pos - 1], &stat_buf) == 0
-              && (geteuid () == stat_buf.st_uid));
+      if (stat (argv[pos - 1], &stat_buf) != 0)
+        return false;
+      errno = 0;
+      uid_t euid = geteuid ();
+      uid_t NO_UID = -1;
+      return ! (euid == NO_UID && errno) && euid == stat_buf.st_uid;
 
     case 'G':			/* File is owned by your group? */
       unary_advance ();
-      return (stat (argv[pos - 1], &stat_buf) == 0
-              && (getegid () == stat_buf.st_gid));
+      if (stat (argv[pos - 1], &stat_buf) != 0)
+        return false;
+      errno = 0;
+      gid_t egid = getegid ();
+      gid_t NO_GID = -1;
+      return ! (egid == NO_GID && errno) && egid == stat_buf.st_gid;
 
     case 'f':			/* File is a file? */
       unary_advance ();