From: David B. Held (dheld_at_[hidden])
Date: 2002-09-05 13:59:41
"Anthony Williams" <anthwil_at_[hidden]> wrote in message
news:15733.50724.159000.285126_at_gargle.gargle.HOWL...
> [...]
> I can see the point, but this is undefined behaviour --- you are returning
> a reference to a temporary, which as gone out of scope.
Good point. So we can just drop in a default singleton, which saves
us a construction anyway, and make the behaviour defined. ;)
// Requirements:
// Ptr must define element_type
// Ptr must provide an implicit conversion to bool
// Ptr::element_type must be default-constructible
template <class Ptr>
typename Ptr::element_type const& safe_dereference(Ptr p)
{
typedef typename Ptr::element_type element_type;
static element_type default_element;
return p ? *p : default_element;
}
// Requirements:
// T must be default-constructible
template <typename T>
T const& safe_dereference(T* p)
{
static T default_T;
return p ? *p : default_T;
}
Dave