How to avoid successive deallocations/allocations in C++?

Question

Consider the following code:

class A
{
    B* b; // an A object owns a B object

    A() : b(NULL) { } // we don\'t know what b will be when constructing A

             


        

Answer 1

Are you sure that memory allocation is the bottleneck you think it is? Is B's constructor trivially fast?

If memory allocation is the real problem, then placement new or some of the other solutions here might well help.

If the types and ranges of the param[1..4] are reasonable, and the B constructor "heavy", you might also consider using a cached set of B. This presumes you are actually allowed to have more than one at a time, that it does not front a resource for example.