The user_from_{uid,gid} routines would return garbage if the

uid/gid in question was in the cache, but did not exist
in the password file.  This causes the -nouser and -nogroup
options to find(1) to only print the first file owned by
an unknown user/group in some cases.

lib/libc/gen/pwcache.c

@@ -79,7 +79,7 @@ user_from_uid(uid, nouser)
 				return (NULL);
 		}
 	}
-	return (cp->name);
+	return (cp->found ? cp->name : NULL);
 }
 
 char *
@@ -115,5 +115,5 @@ group_from_gid(gid, nogroup)
 				return (NULL);
 		}
 	}
-	return (cp->name);
+	return (cp->found ? cp->name : NULL);
 }