C++ Boost library - passing Shared pointer to a function

Question

Assuming shared pointer can be created as follows

typedef boost::shared_ptr<Employee_t> srdpointer;     
srdpointer ptr((Employee_t*)malloc(sizeof(Employee_t)),std::ptr_fun(free));

I need to pass the shared pointer which will allocate memory Pointed by the ptr. Something like this.

void allocateBlocks(int **ptr, int *cnt)
{
    *ptr = (int*)malloc(sizeof(int) * 10);
    *cnt = 10;
    /*do something*/ 
}

int main()
{
    int *p = NULL;
    int count = 0;
    locateBlocks(&p, &count);

    /*do something*/

    free(p);
}

How can I achieve the similar functionality using shared_ptr as shown in above code.

Are you aware, that `reset()`ing `shared_ptr` instance with new pointer, does not change other `shared_ptr` instances (they will point to the old object)? — Greg, Sep 05 '12 at 17:40

duselbaer · Answer 1 · 2012-09-14T11:11:05.297

-1

Do you mean something like this?

void allocateBlocks( boost::shared_ptr<int>& out, int& count )
{
  out.reset(new int[...]);
  count = 10;
}

PS: I suggest having a look at boost::shared_array<> & friends for just allocating arrays dynamically.

PS: Would an std::vector<> also do?

edited Sep 14 '12 at 11:11

answered Sep 05 '12 at 13:51

duselbaer

935
2
6
10

"may I ask why you are using malloc and not new" - Our application is a mix of C and CPP code. – om sarathe Sep 06 '12 at 03:46
-1 Passing `malloc`-ed memory to a construct that will free it with the `delete` operator. – Paul Manta Sep 14 '12 at 06:25

C++ Boost library - passing Shared pointer to a function

1 Answers1