Add JobCoro destructor completion assert

Make JobCoro non copyable

src/ripple/core/JobCoro.h

@@ -39,6 +39,7 @@ struct JobCoro_create_t { };
 
 } // detail
 
+/** Coroutines must run to completion. */
 class JobCoro : public std::enable_shared_from_this<JobCoro>
 {
 private:
@@ -52,6 +53,9 @@ private:
     std::condition_variable cv_;
     boost::coroutines::asymmetric_coroutine<void>::pull_type coro_;
     boost::coroutines::asymmetric_coroutine<void>::push_type* yield_;
+#ifndef NDEBUG
+    bool finished_ = false;
+#endif
 
 public:
     // Private: Used in the implementation
@@ -59,6 +63,12 @@ public:
     JobCoro(detail::JobCoro_create_t, JobQueue&, JobType,
         std::string const&, F&&);
 
+    // Not copy-constructible or assignable
+    JobCoro(JobCoro const&) = delete;
+    JobCoro& operator= (JobCoro const&) = delete;
+
+    ~JobCoro();
+
     /** Suspend coroutine execution.
         Effects:
           The coroutine's stack is saved.

src/ripple/core/JobCoro.ipp

@@ -36,10 +36,19 @@ JobCoro::JobCoro(detail::JobCoro_create_t, JobQueue& jq, JobType type,
             yield_ = &do_yield;
             yield();
             fn(shared_from_this());
+#ifndef NDEBUG
+            finished_ = true;
+#endif
         }, boost::coroutines::attributes (1024 * 1024))
 {
 }
 
+inline
+JobCoro::~JobCoro()
+{
+    assert(finished_);
+}
+
 inline
 void
 JobCoro::yield() const