Using malloc instead of new, and calling the copy constructor when the object is created

Question

I wanted to try out TBB\'s scalable_allocator, but was confused when I had to replace some of my code. This is how allocation is done with the allocator:

Som         


        

Answer 1

You'll need to use placement new after getting the raw memory from malloc.

void* mem = malloc(sizeof(S));
S* s = new (mem) S(); //this is the so called "placement new"

When you're done with the object you have to make sure to explicitly call its destructor.

s->~S();
free(mem);