Mixing C++ and C

I have an existing ANSI C library which makes extensive use of structs.
I use these structs in my C++ code, but would like to benefit from C++
features such as ctors/dtors etc. I have modified the C header, as shown
below, with inline functions, so that I can benefit from C++ features,
whilst keeping the rest of the C library intact.

One thing I had to be particularly careful of is the fact that in a lot
of the C API functions, struct assignments were made (i.e. shallow
copies). I have therefore implemented the (overloaded) assignment
operator to create 'shallow' copy by default (so this is consistent with
the C API so that a pointer to the struct could be passed to a C API
function with no adverse effect). The facility still exists for an
(explicit) deepcopy. This is is what I have come up with so far. The CPP
snippet at the end of the post shows how I intend to use it.

//Header File

#ifdef __cplusplus
extern "C"
{
#endif

struct MyStruct
{
public:
    MyStruct(const size_t size)
    :m_shallow_copied(false)
    {
        if (!fooAlloc(this, size))
            throw new std::bad_alloc ;
    }

    MyStruct(const MyStruct& ms)
    :m_shallow_copied(false)
    {
        //deep copy because only C++ API calls this ctor
        copy(ms, true);
    }

    MyStruct& operator= (const MyStruct& rhs)
    {
        //Default shallow copy on assignments
        if (this != &rhs)
            copy(rhs);
        return *this ;
    }

    //explicit deepcopy
    void deepcopy(const struct MyStruct* rhs)
    {
        copy(rhs,true);
    }

    ~MyStruct::MyStruct
    {
        if (!m_shallow_copied && m_ptr)
            fooFree(this);
    }

    //Needs to be public - for C API (too many funcs to all be friends)
    void * m_ptr ;
    size_t m_size ;

private:
    void copy(const MyStruct& rhs, const bool deepcopy=false)
    {
        if (deepcopy)
        {
            //do we own ptr? (if so, free first)
            if (m_ptr && !m_shallow_copied)
                fooFree(this);

            if (fooAlloc(this, rhs.size ))
                throw new std::bad_alloc ;

            fooCopy(this, &rhs) ;
            m_shallow_copied = false ;
        }
        else
        {
            //default
            m_ptr = rhs.m_ptr ;
            m_size = rhs.m_size ;
            m_shallow_copied = true ;
        }
    }

    bool m_shallow_copied ;
};

/* Pure C API */
long fooAlloc(struct MyStruct* ms, const unsigned int size);
void fooFree(struct MyStruct* ms);
void fooCopy(struct MyStruct* dest, const struct MyStruct* src);
long fooJustDoIt(const struct MyStruct* ms);

#ifdef __cplusplus
};
#endif

//Sample cpp file using MyStruct (should probably use auto_ptr instead
of raw pointers ...)

#include "MyStruct.h"

class MyClass
{
public:
     MyClass(const size_t s)
     { ms = new MyStruct(s); }

     MyClass(const MyClass&);

     ~MyClass()
     {delete ms ;}

     long DoSomething() const
     {
    //pass ptr to MyStruct to C function
         return fooJustDoIt(ms);
     }

private:
    MyStruct * ms ;
};

I would appreciate some feedback as to whether there are any subtle (or
not so subtle) caveats/gotchas I must be aware of with this approach ...