Manually incrementing and decrementing a boost::shared_ptr?

Question

Is there a way to manually increment and decrement the count of a shared_ptr in C++?

The problem that I am trying to solve is as follows. I am writing a library in C

Answer 1

Another option would be to just allocate dynamically a copy of the shared_ptr, in order to increment the refcount, and deallocate it in order to decrement it. This guarantees that my shared object will not be destroyed while in use by the C api client.

In the following code snippet, I use increment() and decrement() in order to control a shared_ptr. For the simplicity of this example, I store the initial shared_ptr in a global variable.

#include 
#include 
#include 
#include 
using namespace std;

typedef boost::shared_ptr MySharedPtr;
MySharedPtr ptr = boost::make_shared(123);

void* increment()
{
    // copy constructor called
    return new MySharedPtr(ptr);
}

void decrement( void* x)
{
    boost::scoped_ptr< MySharedPtr > myPtr( reinterpret_cast< MySharedPtr* >(x) );
}

int main()
{
    cout << ptr.use_count() << endl;
    void* x = increment();
    cout << ptr.use_count() << endl;
    decrement(x);
    cout << ptr.use_count() << endl;

    return 0;
}

Output:

1
2
1