Question

I want to share some objects between multiple programs using shared memory.

I’ve found example at this site. It doesn’t have any allocation of object, just direct addressing, but i want to create struct or class in shared memory.

Answer 1

Because the memory is already allocated you want to use placement new:

void * ptr = shmat(shmid, 0, 0);
// Handle errors
MyClass * x = new (ptr) MyClass;

Then, the new instance of MyClass will be constructed in memory pointed by ptr.

When the object is not needed, you have to manually call the destructor (without freeing the memory).

ptr->MyClass::~MyClass();