Nim-1.6 fixes (#239)

chronos/asyncloop.nim

@@ -323,7 +323,7 @@ when defined(windows) or defined(nimdoc):
     AsyncFD* = distinct int
 
   proc hash(x: AsyncFD): Hash {.borrow.}
-  proc `==`*(x: AsyncFD, y: AsyncFD): bool {.borrow.}
+  proc `==`*(x: AsyncFD, y: AsyncFD): bool {.borrow, gcsafe.}
 
   proc getFunc(s: SocketHandle, fun: var pointer, guid: var GUID): bool =
     var bytesRet: DWORD
@@ -516,7 +516,7 @@ elif unixPlatform:
       selector: Selector[SelectorData]
       keys: seq[ReadyKey]
 
-  proc `==`*(x, y: AsyncFD): bool {.borrow.}
+  proc `==`*(x, y: AsyncFD): bool {.borrow, gcsafe.}
 
   proc globalInit() =
     # We are ignoring SIGPIPE signal, because we are working with EPIPE.

chronos/asyncsync.nim

@@ -571,8 +571,10 @@ proc emit[T](bus: AsyncEventBus, event: string, data: T, loc: ptr SrcLoc) =
 
     # Schedule subscriber's callbacks, which are subscribed to the event.
     for subscriber in item.subscribers:
+      # Nim-1.6 says: "'subscriber' is of type <lent EventBusKey> which cannot be captured as it would violate memory safety"
+      let subscriber_copy = subscriber
       callSoon(proc(udata: pointer) =
-        subscriber.cb(bus, event, subscriber, payload)
+        subscriber_copy.cb(bus, event, subscriber_copy, payload)
       )
 
   # Schedule waiters which are waiting all events
@@ -583,8 +585,10 @@ proc emit[T](bus: AsyncEventBus, event: string, data: T, loc: ptr SrcLoc) =
 
   # Schedule subscriber's callbacks which are subscribed to all events.
   for subscriber in bus.subscribers:
+    # Nim-1.6 says: "'subscriber' is of type <lent EventBusKey> which cannot be captured as it would violate memory safety"
+    let subscriber_copy = subscriber
     callSoon(proc(udata: pointer) =
-      subscriber.cb(bus, event, subscriber, payload)
+      subscriber_copy.cb(bus, event, subscriber_copy, payload)
     )
 
 template emit*[T](bus: AsyncEventBus, event: string, data: T) =

chronos/transports/stream.nim

@@ -1642,7 +1642,7 @@ else:
           break
     return retFuture
 
-  proc acceptLoop(udata: pointer) =
+  proc acceptLoop(udata: pointer) {.gcsafe.} =
     var
       saddr: Sockaddr_storage
       slen: SockLen