Re: Why is nullptr unsafe?

Hi,

I implemented the nullptr workaround found here in Section 1.1.
http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2007/n2431.pdf

However, I get some nasty behavior when initializing static variables.
Here is the code.

// From N2431, Section 1.1.
const
class
{
public:
   template<class T>
   operator T*() const { return 0; }

   template<class C, class T>
   operator T C::*() const { return 0; }

private:
   void operator&() const;

} nullptr = {};

// My test (in the same file).

#include <iostream>
#include <assert.h>

template<typename T>
class StaticInit
{
public:
   static T& value()
   {
      std::cerr << "value() - "
         << "Initialied: " << initialized_
         << " Pointer: " << pointer_ << std::endl;

      if( initialized_ == false )
      {
         pointer_ = new T;
         initialized_ = true;
      }
      assert( pointer_ );
      return *pointer_;
   }

private:
   static T* pointer_;
   static bool initialized_;
};

template<typename T>
T* StaticInit<T>::pointer_ = nullptr;

template<typename T>
bool StaticInit<T>::initialized_ = false;

typedef StaticInit<int> SIInt;

struct SomeClass
{
   SomeClass() { SIInt::value() = 47; }

} someClass; // NOTE! Static variable calling SIInit.

struct SomeClass2
{
   SomeClass2() { SIInt::value() = 11; }

} someClass2; // NOTE! Static variable calling SIInit.

int main()
{
   std::cerr << SIInt::value() << std::endl;
}

When I run this program I get two initializations of pointer_. First I
get the mandatory zero-initialization [?3.6.2/2]. Then I get pointer_
initialized when SIInt::value() is called from SomeClass. After that I
get pointer_ initialized again with nullptr!