Check is allocation in event queue was success or not, and

report error / assert when allocation fails.

events/EventQueue.cpp

@@ -16,6 +16,7 @@
  */
 #include "events/EventQueue.h"
 #include "events/mbed_events.h"
+#include "platform/mbed_assert.h"
 
 using mbed::Callback;
 
@@ -74,9 +75,9 @@ void EventQueue::background(Callback<void(int)> update)
 void EventQueue::chain(EventQueue *target)
 {
     if (target) {
-        equeue_chain(&_equeue, &target->_equeue);
+        MBED_ASSERT(equeue_chain(&_equeue, &target->_equeue) == 0);
     } else {
-        equeue_chain(&_equeue, 0);
+        MBED_ASSERT(equeue_chain(&_equeue, 0) == 0);
     }
 }
 }

events/equeue/equeue.c

@@ -605,19 +605,23 @@ static void equeue_chain_update(void *p, int ms)
     }
 }
 
-void equeue_chain(equeue_t *q, equeue_t *target)
+int equeue_chain(equeue_t *q, equeue_t *target)
 {
     if (!target) {
         equeue_background(q, 0, 0);
-        return;
+        return 0;
     }
 
     struct equeue_chain_context *c = equeue_alloc(q,
                                                   sizeof(struct equeue_chain_context));
+    if (!c) {
+        return -1;
+    }
 
     c->q = q;
     c->target = target;
     c->id = 0;
 
     equeue_background(q, equeue_chain_update, c);
+    return 0;
 }

events/equeue/equeue.h

@@ -220,7 +220,10 @@ void equeue_background(equeue_t *queue,
 //
 // The equeue_chain function allows multiple equeues to be composed, sharing
 // the context of a dispatch loop while still being managed independently.
-void equeue_chain(equeue_t *queue, equeue_t *target);
+//
+// If the event queue chaining fails, equeue_chain returns a negative,
+// platform-specific error code.
+int equeue_chain(equeue_t *queue, equeue_t *target);
 
 
 #ifdef __cplusplus