Does std::make_shared() use custom allocators?

Question

Consider this code:

#include 
#include 


class SomeClass {
public:
    SomeClass() {
        std::cout << \"SomeClass()\" &l         


        

Answer 1

Yes, this is standard behavior. From the standard (§20.7.2.2.6 shared_ptr creation ):

Effects: Allocates memory suitable for an object of type T and constructs an object in that memory via the placement new expression ::new (pv) T(std::forward(args)...).

This allows make_shared to allocate the storage for both the object and the data structure for the shared pointer itself (the "control block") in a single allocation, for efficiency reasons.

You could use std::allocate_shared if you want to control that storage allocation.