c++ - How should I manage my memory in cpp with calling a C-style interface?

Question

I want to manage pointer with smart pointer in my code, however I must call old C-style interface to get pointer, like that:

void getPointer(T** pT, int* pSize);

Users pass an empty pointer of Pt and return a pointer, I want to manage it with smart pointer in my code like

std::shared_ptr<T> ptr;

How should I write my code? I have been told that use get() method is not a safe idea. Another question is, how should I safely copy memory stored in smart pointer to a raw pointer? (or vice)

question from:https://stackoverflow.com/questions/65842454/how-should-i-manage-my-memory-in-cpp-with-calling-a-c-style-interface

Answer 1

You can construct a std::shared_ptr<T> (or a std::shared_ptr<T[]>) from a T*. If the T(s) weren't allocated with new([]), you will need to provide the correct deallocation to the shared pointer.

Assuming that there is a void returnPointer(T* pT, int size); in that C interface.

struct C_interface_deleter {
    void operator()(T* ptr) { returnPointer(ptr, size); }
    int size;
};

void use_C_interface() {
    T* raw;
    int size;
    getPointer(&raw, &size);
    std::shared_ptr<T> ptr(raw, C_interface_deleter{ size });

    // stuff involving ptr
}