How to stop heap memory allocation for class in case of make_shared

Question

Hi

Refer code below:
https://code.sololearn.com/cUe01sBygcuy

Observed that I have overloaded operator new inside class and upon code execution, I am getting custom allocation cout statement once only for raw pointer, that is clsTest* p

I dont get custom allocation for make_shared i.e. for sp1.

I wanted to make this overloaded new operator private so that we can stop memory allocation on heap for class. but doing so, I am able to allocate memory on heap using make_shared as it is not calling class overloaded new operator.

Is there a way to do so?

P.S. : If i have class without any operator overloading of new and with new operator overloaded at global level, make_shared and raw pointer both allocates memory from global operator overloaded.

Answer 1

To stop heap memory allocation for class in case of make_shared, you can use the std::allocate_shared function instead of std::make_shared. The std::allocate_shared function takes an allocator as its first argument, and the allocator will be used to allocate the memory for the object. This means that you can use a custom allocator to allocate the memory on the stack instead of the heap.

For example, the following code shows how to use std::allocate_shared to allocate a clsTest object on the stack:

#include <iostream>
#include <memory>

using namespace std;

class clsTest
{
public:
clsTest() { cout << "Constructor\n"; }
~clsTest() { cout << "Destructor\n"; }
};

int main()
{
{
// Allocate a `clsTest` object on the stack.
shared_ptr<clsTest> sp1 = allocate_shared<clsTest>();
}

return 0;
}

Note that the std::allocate_shared function is not part of the C++ standard library. It is part of the C++11 TR (Technical Report), which is a draft of the C++11 standard. However, most compilers support the std::allocate_shared function.