Eu tirei dos livros de Scott Meyers
#if defined(_MSC_VER)
#define ALWAYS_INLINE __forceinline
#elif defined(__GNUC__)
#define ALWAYS_INLINE inline __attribute__((always_inline))
#else
#define ALWAYS_INLINE inline
#endif
/**
* Anonymous class, to be used instead of <code>0</code> or <code>NULL</code>.
* Enables the selection of the correct form when methods are overloaded for
* both pointers & integrals types.
*/
const class
{
public:
#if defined(__GNUC__) && (__GNUC__ == 4) && (__GNUC_MINOR__ == 5) && (__GNUC_PATCHLEVEL < 2)
ALWAYS_INLINE operator void*() const // works around bug #45383
{
return 0;
}
#endif // #if defined(__GNUC__) && (__GNUC__ == 4) && __(__GNUC_MINOR__ == 5) && (__GNUC_PATCHLEVEL < 3)
template<typename T>
ALWAYS_INLINE operator T*() const
{
return 0;
}
template<class C, typename T>
ALWAYS_INLINE operator T C::*() const
{
return 0;
}
private:
void operator &() const; // not implemented on purpose
} nullptr = {}; // the empty brace initializer fills the ISO C++
// (in 8.5 [dcl.ini] paragraph 9) requirements:
//
// If no initializer is specified for an object, and the
// object is of (possibly cv-qualified) non-POD class
// type (or array thereof), the object shall be
// default-initialized; if the object is of
// const-qualified type, the underlying class type shall
// have a user-declared default constructor