Re: Making a smart pointer which works with incomplete types
* Kai-Uwe Bux:
Alf P. Steinbach wrote:
* Juha Nieminen:
Then it occurred to me: Is there any reason this pointer cannot be
static? Like this:
//------------------------------------------------------------------
template<typename Data_t>
class SmartPointer
{
...
static void(*deleterFunc)(Data_t*);
...
public:
SmartPointer(Data_t* d): data(d)
{
deleterFunc = &deleter;
}
...
};
template<typename Data_t>
void(*SmartPointer<Data_t>::deleterFunc)(Data_t*) = 0;
//------------------------------------------------------------------
This way the pointer to the deleter will be stored in the program only
once, and most importantly it will not increment the size of the smart
pointer.
This feels so glaringly obvious to me now that I really wonder why
this wasn't suggested to me to begin with. Is there some error here I'm
missing?
Yeah. Successive smart pointer instantiations can change the common
deleter func pointer.
[snip]
How?
Sorry, I reacted to the static pointer. As I wrote use a template parameter
instead. The only valid reason for having a pointer to that function is to
change the pointer, and that's apparently done in the constructor body, so I
read the constructor argument as pointer to func (didn't really read it, I only
inferred the only thing that could make sense, assuming the code was sensible).
As I wrote, use a template parameter.
The static pointer doesn't make sense, and having a nonsensical thing in there
causes people like me to draw incorrect conclusions about the code (we don't
actually read it, we just look at it, like e.g. someone good at chess might look
at a randomly generated chess position and assume that it's sensible and draw
wrong conclusions).
Cheers,
- Alf
--
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