Added some more tests for the thread_pool object.

--HG--
extra : convert_revision : svn%3Afdd8eb12-d10e-0410-9acb-85c331704f74/trunk%402681

dlib/test/thread_pool.cpp

@@ -25,6 +25,16 @@ namespace
         float val;
     };
 
+    struct add_functor
+    {
+        template <typename T, typename U, typename V>
+        void operator()(T a, U b, V& res)
+        {
+            dlib::sleep(20);
+            res = a + b;
+        }
+    };
+
     void gset_struct_to_zero (some_struct& a) { a.val = 0; }
     void gset_to_zero (int& a) { a = 0; }
     void gincrement (int& a) { ++a; }
@@ -44,7 +54,9 @@ namespace
         void perform_test (
         )
         {
-            thread_pool tp(3);
+            for (int num_threads= 0; num_threads < 4; ++num_threads)
+            {
+                thread_pool tp(num_threads);
                 print_spinner();
 
                 future<int> a, b, c, res;
@@ -176,6 +188,16 @@ namespace
                     DLIB_CASSERT(obj.get().val == 8,"");
                     tp.add_task(*this,&thread_pool_tester::set_struct_to_zero, obj);
                     DLIB_CASSERT(obj.get().val == 0,"");
+
+                    a = 1;
+                    b = 2;
+                    res = 0;
+                    add_functor f;
+                    tp.add_task(f, a, b, res);
+                    DLIB_CASSERT(a == 1,"");
+                    DLIB_CASSERT(b == 2,"");
+                    DLIB_CASSERT(res == 3,"");
+                }
             }
         }