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, 4 insertions, 1 deletions

diff --git a/src/su.c b/src/su.c
index 081ecb2eb..b1ba2a7b7 100644
--- a/src/su.c
+++ b/src/su.c
@@ -173,7 +173,10 @@ log_su (struct passwd const *pw, bool successful)
     {
       /* getlogin can fail -- usually due to lack of utmp entry.
          Resort to getpwuid.  */
-      struct passwd *pwd = getpwuid (getuid ());
+      errno = 0;
+      uid_t ruid = getuid ();
+      uid_t NO_UID = -1;
+      struct passwd *pwd = (ruid == NO_UID && errno ? NULL : getpwuid (ruid));
       old_user = (pwd ? pwd->pw_name : "");
     }
   tty = ttyname (STDERR_FILENO);