Do not try to lock "/dev/null" mailboxes. These are used in several

programs (namely, comsat, imap4d, pop3d).

@@ -98,14 +98,16 @@ locker_create (locker_t *plocker, const char *filename, int flags)
 
   if(!l->dotlock)
     {
-    free(l->file);
-    free(l);
+      free (l->file);
+      free (l);
       return ENOMEM;
     }
 
   sprintf(l->dotlock, "%s.lock", l->file);
 
-  if (flags)
+  if (strcmp (filename, "/dev/null") == 0)
+    l->flags = MU_LOCKER_NULL;
+  else if (flags)
     l->flags = flags;
   else
     l->flags = MU_LOCKER_DEFAULT;
@@ -344,8 +346,10 @@ locker_lock (locker_t lock)
   if (lock == NULL)
     return EINVAL;
 
-  INVARIANT (lock);
+  if (lock->flags == MU_LOCKER_NULL)
+    return 0;
   
+  INVARIANT (lock)
     /* Is the lock already applied? */
   if (lock->refcnt > 0)
     {
@@ -511,6 +515,9 @@ locker_touchlock (locker_t lock)
   if (!lock)
     return MU_ERR_LOCKER_NULL;
 
+  if (lock->flags == MU_LOCKER_NULL)
+    return 0;
+  
   assert(lock->dotlock);
 
   INVARIANT(lock);
@@ -524,6 +531,12 @@ locker_touchlock (locker_t lock)
 int
 locker_unlock (locker_t lock)
 {
+  if (!lock)
+    return MU_ERR_LOCKER_NULL;
+
+  if (lock->flags == MU_LOCKER_NULL)
+    return 0;
+  
   assert(lock->refcnt >= 0);
 
   if (!lock)
@@ -549,6 +562,7 @@ locker_unlock (locker_t lock)
 
   return 0;
 }
+
 int
 locker_remove_lock (locker_t lock)
 {
@@ -557,6 +571,9 @@ locker_remove_lock (locker_t lock)
   if (!lock)
     return MU_ERR_LOCKER_NULL;
 
+  if (lock->flags == MU_LOCKER_NULL)
+    return 0;
+  
   INVARIANT(lock);
 
   /* If we hold the lock, do an unlock... */