nse/client: Only call 'send-start!' after 'mq' has been defined.

This addresses a theoretical race condition.

* gnu/gnunet/nse/client.scm
  (connect)[mq-defined]: New variable.
  (connect)[error-handler]: Wait on new variable.
  (connect)[mq]: Signal new condition after 'mq' is defined.

1 files changed, 8 insertions, 0 deletions

diff --git a/gnu/gnunet/nse/client.scm b/gnu/gnunet/nse/client.scm
index 194eaac..4420d23 100644
--- a/gnu/gnunet/nse/client.scm
+++ b/gnu/gnunet/nse/client.scm
@@ -44,6 +44,8 @@
                 make-atomic-box atomic-box-ref atomic-box-set!)
           (only (fibers)
                 spawn-fiber)
+          (only (fibers conditions)
+                make-condition wait signal-condition!)
           (only (gnu extractor enum)
                 symbol-value value->index)
           (only (guile)
@@ -152,10 +154,15 @@ The procedures @var{updated}, @var{connected} and @var{disconnected} are optiona
         (set%! /:message-header '(type) s
                (value->index (symbol-value message-type msg:nse:start)))
         (send-message! mq s))
+      (define mq-defined (make-condition))
       (define (error-handler error)
         (case error
           ;; TODO report input errors?
           ((connection:connected)
+           ;; Make sure the message queue is actually bound to the variable
+           ;; @var{mq} before calling @code{send-start!}, as @code{send-start!}
+           ;; uses @var{mq}.
+           (wait mq-defined)
            (send-start!)
            (when connected (connected)))
           ;; TODO this means the server has closed the connection ...
@@ -165,4 +172,5 @@ The procedures @var{updated}, @var{connected} and @var{disconnected} are optiona
            (values))))
       (define mq (connect/fibers config "nse" handlers error-handler
                                  #:spawn spawn))
+      (signal-condition! mq-defined)
       (%make-server estimate/box))))