Re: [boost] intrusive_ptr and overloading not working under VC++ 8

10 Dec 2005

      Stefan Popov wrote:
...
I ran onto a problem when using intrusive_ptr, overloading and MS
visual studio 8
All my classes derive a reference counted class RefCnt. For example:
class GLTexture : public RefCnt {...};
class GLRenderBuffer : public RefCnt {...};
I define smart pointers using the intrusive_ptr class:
typedef boost::intrusive_ptr<GLTexture> GLTexturePtr;
typedef boost::intrusive_ptr<GLRenderBuffer> GLRenderBufferPtr;
Than I define a function accepting both GLTexturePtr and
GLRenderBufferPtr :
void attachTarget(GLTexturePtr aTexture);
void attachTarget(GLRenderBufferPtr aBuffer);
invoking <code>attach(new GLTexture)</code> leads to an error:
ambiguous function call.
The reason is in the contructor of intrusive_ptr:
   template<class U> intrusive_ptr(intrusive_ptr<U> const & rhs) ...
which allows an invocation with an unrelated pointer.
This program:

#include <boost/intrusive_ptr.hpp>

class RefCnt
{
};

void intrusive_ptr_add_ref( RefCnt * );
void intrusive_ptr_release( RefCnt * );

class GLTexture: public RefCnt
{
};

class GLRenderBuffer: public RefCnt
{
};

typedef boost::intrusive_ptr<GLTexture> GLTexturePtr;
typedef boost::intrusive_ptr<GLRenderBuffer> GLRenderBufferPtr;

void attachTarget(GLTexturePtr aTexture);
void attachTarget(GLRenderBufferPtr aBuffer);

int main()
{
    attachTarget( new GLTexture );
}

compiles for me under MSVC 8.

Re: [boost] intrusive_ptr and overloading not working under VC++ 8

Peter Dimov