Allocating class member with std::shared_ptr

Question

Is my assumption, that in following example, memory referenced by b will be deallocated once instance of A goes out of scope at end of func(), correct?

class A{
public:
   A() {
        b = std::shared_ptr<char>(new char[100] { 0 } );
   }
   char* b;
}

void func {
   A a;
}

Answer 1

No, not correct. b is of type char * and you assign to it a shared_ptr<char>. You should get a compilation error.

Furthermore, the constructor is private, another compilation error.

And how do you access b in func()? It is private in A.

Obviously your exercise is incomplete... so I just go from what you provided.

Also I suggest to use unique_ptr in case you can say it is a unique ownership (which it appears to be in my opinion).

This compiles:

#include <memory>
#include <iostream>

class A {
public:

    A() {
        std::cout << "A created with unique pointer" << std::endl;
        b = std::unique_ptr<char>(new char[100] {
            0
        });
    }

    ~A() {
        std::cout << "A destroyed" << std::endl;
    }

private:
    std::unique_ptr<char> b;
};

void func() {
    A a;
}

int main() {
    std::cout << "Call func()" << std::endl;
    func();
    std::cout << "func() called" << std::endl;
    return 0;
}

And at the end of func() A is destroyed and with it the unique_ptr.

However, ask yourself if you really need to use pointer? In your case an automatic variable should be just fine; it does the same (i.e. being destroyed when func() exits.