a compiation issue with gcc

Eljay Love-Jensen eljay@adobe.com
Thu May 19 13:12:00 GMT 2005


Hi Damanjit,

I see a few unrelated problems with your code.

1)
#include "iostream.h" is not C++ compliant (it's deprecated at best).  Use #include <iostream>.  Since it wasn't used in your code example, I removed it.

2)
#include "stdio.h" is not C++ compliant (it's deprecated at best).  Use #include <cstdio>.  Since it wasn't used in your code example, I removed it.

3)
With GCC, you should compile C++ code with the g++ front end, not with gcc.

Now on to the meat of the problem.

4)
You appear to be replicating std::auto_ptr, which is part of Standard C++ in the C++ <memory> header.  But maybe you have a simplified example for illustrative purposes, so just consider this an FYI.

5)
You were missing the header for free().  I added #include <cstdlib>.  Instead of using <cstdlib>'s malloc / free for your heap memory management, I strongly recommend using C++ new / delete.  But that may be an aside from your actual problem at hand.

6)
You are passing in a function pointer as a template type parameter.  I vaguely recall there can be issues with function pointers (especially ones that are static-at-the-translation-unit level, or static-at-the-class-level).

As an alternative for you consideration (which will be more digestible / less problematic amongst a variety of C++ compilers at different levels of C++ compliance), you could use a functor object.  Functor objects tend to be a lot more C++ friendly in general, anyway -- but may or may not be suitable for your needs.

That could look something like this:
--------------------------------------
#include <cstdlib> // free

template <class T, class DestroyFunctor>
class B
{
private:
    T a;
};

template <class T>
class A
{
private:
    void operator ()(T Ptr)
    {
        free(Ptr);
    }

public:
    typedef B<T, A<T> > Type;
};

int main()
{
    A<int*> a;
    return 0;
}
--------------------------------------

HTH,
--Eljay



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