Stack overflow on heap allocation

Question

What exactly is going on here?

#include <boost/array.hpp>
#include <boost/assign/list_of.hpp>

struct Toy {
    int m_data[100000];
};

struct Box {
    Box()
        : m_toys(  boost::assign::list_of( Toy() )( Toy() )( Toy() )  )
    {}

    boost::array<Toy,3>   m_toys;
};

void main()
{
    Box* box = new Box; // This causes stack overflow
}

Answer 1

The problem is that the objects Toy()are being passed in boost::assign::list_of(). These are temporary objects that are created on the stack before being copied to the object Box(which will be on the heap)

to avoid creating them on the stack, you can do this:

Box() : m_toys()
{
   Toy* t = new Toy;
   for (int i = 0; i < 3; ++i)
       m_toys.push_back(*t);
   delete t;
}

Answer 2

Value

boost::assign::list_of( Toy() )( Toy() )( Toy() )

generates a (huge) temporary stack (woo!), which is passed to the constructor for toys.

Answer 3

Box(). , boost:: , , , , Toy. , , .