I'm having some trouble with using shared_ptr, auto_ptr and
enable_shared_from_this with my inheritance layout. The following is
how my inheritance is laid out.
// Inheritance Layout
//
// boost::enable_shared_from_this<T>
// ^
// |
// Base --------> IBase
// ^
// |
// Derived -----> IDerived
In my test code (that I've included with this email) the following two
ways to instantiate a shared pointer is equivalent.
boost::shared_ptr<IDerived> r (new Derived());
std::auto_ptr<IDerived> k (new Derived);
boost::shared_ptr<IDerived> l (k.release());
When creating the shared_ptr, both declaration take me to line 185 of
shared_ptr.hpp. Instantiating the shared_ptr directly then takes me to
line 105 of shared_ptr.hpp. Though when instantiating by releasing the
auto_ptr into the shared_ptr I'm taken to line 129. It seems to me that
I should be going to the same line of code. This wouldn't be such a
problem except when trying to call shared_from_this() an exception is
thrown if my shared_ptr was created from an auto_ptr. Is this behavior
correct?
Ryan
#include <iostream>
#include <memory>
#include
#include
// Inheritance Layout
//
// boost::enable_shared_from_this<T>
// ^
// |
// Base --------> IBase
// ^
// |
// Derived -----> IDerived
class IBase
{
public:
virtual void hello(void) = 0;
};
class Base : public IBase, public boost::enable_shared_from_this<Base>
{
public:
Base(void){}
~Base(void){}
void hello(void)
{
std::cout << "Hello" << std::endl;
}
};
class IDerived
{
public:
virtual void world(void) = 0;
static std::auto_ptr<IDerived> createAuto(void);
static boost::shared_ptr<IDerived> createShared(void);
virtual boost::shared_ptr<Base> root(void) = 0;
virtual boost::shared_ptr<IBase> root2(void) = 0;
};
class Derived : public IDerived, public Base
{
public:
Derived(void){}
~Derived(void){}
void world(void)
{
std::cout << "World" << std::endl;
}
virtual boost::shared_ptr<Base> root(void)
{
return shared_from_this();
}
virtual boost::shared_ptr<IBase> root2(void)
{
return shared_from_this();
}
};
std::auto_ptr<IDerived> IDerived::createAuto(void)
{
return std::auto_ptr<IDerived>(new Derived());
}
boost::shared_ptr<IDerived> IDerived::createShared(void)
{
return boost::shared_ptr<IDerived>(new Derived());
}
int main(int argc, char* argv[])
{
boost::shared_ptr<IDerived> c = IDerived::createShared();
boost::shared_ptr<IBase> d = c->root2();
std::cout << c.use_count() << std::endl;
boost::shared_ptr<IDerived> r (new Derived());
std::auto_ptr<IDerived> k (new Derived);
boost::shared_ptr<IDerived> l (k.release());
boost::shared_ptr<IBase> m = l->root2();
std::cout << m.use_count() << std::endl;
return 0;
}
