Re: curiosity singleton pattern?

 James Kanze <>
Thu, 02 Aug 2007 07:11:28 -0000
On Aug 1, 11:06 am, Chris Forone <> wrote:

cant understand the following:

Scene* Scene::sole(0); // in Scene.cpp

class Scene // singleton in Scene.h
     static Scene* Get()
       //return sole ? sole : new (std::nothrow) Scene;
       return sole; // for testing purposes only

     int Print(void) // normaly only with valid objects?!
       return reinterpret_cast<unsigned int>(sole);
       // other values also possible (return 10;)


     static Scene* sole;

int main(void)
   std::cout << Scene::Get() << std::endl;
   std::cout << Scene::Get()->Print() << std::endl;



non static func Print is called by nullpointer?! have gcc 4.1
and linux os.

It's undefined behavior. Anything might happen. In practice,
on a modern general purpose machine, you will either get the
above results, or some sort of runtime error. Possibly
depending on the options you've passed to the compiler.

James Kanze (GABI Software)
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