Lazy instantiation of threadpool shared instance.

Lazy instantiation of thread pool shared instance enable forking linux processes using cpp rest library as long as the thread pool is not used before the fork.

Author: Simon Lepasteur

Release/include/pplx/threadpool.h

@@ -72,14 +72,9 @@ class threadpool
         for (size_t i = 0; i < n; i++)
             add_thread();
     }
-#if defined(__ANDROID__)
+
     static threadpool& shared_instance();
-#else
-    static threadpool& shared_instance()
-    {
-        return s_shared;
-    }
-#endif
+
     ~threadpool()
     {
         m_service.stop();
@@ -105,10 +100,6 @@ class threadpool
 private:
     struct _cancel_thread { };
 
-#if !defined(__ANDROID__)
-    static threadpool s_shared;
-#endif
-
     void add_thread()
     {
         pthread_t t;

Release/src/pplx/threadpool.cpp

@@ -61,7 +61,11 @@ threadpool& threadpool::shared_instance()
 #else
 
 // initialize the static shared threadpool
-threadpool threadpool::s_shared(40);
+threadpool& threadpool::shared_instance()
+{
+    static threadpool s_shared(40);
+    return s_shared;
+}
 
 #endif