diff --git a/lib/system/inboxes.nim b/lib/system/inboxes.nim
index 1f5d56c16..7b522c7ae 100644..100755
--- a/lib/system/inboxes.nim
+++ b/lib/system/inboxes.nim
@@ -7,8 +7,12 @@
 #    distribution, for details about the copyright.

 #

 

-## Message passing for threads. The current implementation is slow and does

-## not work with cyclic data structures. But hey, it's better than nothing.

+## Message passing for threads. **Note**: This is part of the system module.

+## Do not import it directly. To activate thread support you need to compile

+## with the ``--threads:on`` command line switch.

+##

+## **Note:** The current implementation of message passing is slow and does

+## not work with cyclic data structures.

 

 type

   pbytes = ptr array[0.. 0xffff, byte]

@@ -18,6 +22,7 @@ type
     lock: TSysLock

     cond: TSysCond

     elemType: PNimType

+    ready: bool

     region: TMemRegion

   PInbox = ptr TInbox

   TLoadStoreMode = enum mStore, mLoad

@@ -178,9 +183,7 @@ template lockInbox(q: expr, action: stmt) =
   action

   releaseSys(q.lock)

 

-proc send*[TMsg](receiver: var TThread[TMsg], msg: TMsg) =

-  ## sends a message to a thread. `msg` is deeply copied.

-  var q = cast[PInbox](getInBoxMem(receiver))

+template sendImpl(q: expr) =  

   if q.mask == ThreadDeadMask:

     raise newException(EDeadThread, "cannot send message; thread died")

   acquireSys(q.lock)

@@ -192,12 +195,24 @@ proc send*[TMsg](receiver: var TThread[TMsg], msg: TMsg) =
   releaseSys(q.lock)

   SignalSysCond(q.cond)

 

+proc send*[TMsg](receiver: var TThread[TMsg], msg: TMsg) =

+  ## sends a message to a thread. `msg` is deeply copied.

+  var q = cast[PInbox](getInBoxMem(receiver))

+  sendImpl(q)

+

+proc send*[TMsg](receiver: TThreadId[TMsg], msg: TMsg) =

+  ## sends a message to a thread. `msg` is deeply copied.

+  var q = cast[PInbox](getInBoxMem(receiver[]))

+  sendImpl(q)

+

 proc llRecv(res: pointer, typ: PNimType) =

   # to save space, the generic is as small as possible

   var q = cast[PInbox](getInBoxMem())

   acquireSys(q.lock)

+  q.ready = true

   while q.count <= 0:

     WaitSysCond(q.cond, q.lock)

+  q.ready = false

   if typ != q.elemType:

     releaseSys(q.lock)

     raise newException(EInvalidValue, "cannot receive message of wrong type")

@@ -215,4 +230,15 @@ proc peek*(): int =
   lockInbox(q):

     result = q.count

 

+proc peek*[TMsg](t: var TThread[TMsg]): int =

+  ## returns the current number of messages in the inbox of thread `t`.

+  var q = cast[PInbox](getInBoxMem(t))

+  if q.mask != ThreadDeadMask:

+    lockInbox(q):

+      result = q.count

+

+proc ready*[TMsg](t: var TThread[TMsg]): bool =

+  ## returns true iff the thread `t` is waiting on ``recv`` for new messages.

+  var q = cast[PInbox](getInBoxMem(t))

+  result = q.ready