C++ interview questions and answers

If I write a destructor, copy constructor, or copy assignment, I likely need all three.

Resource acquisition is initialization: the constructor takes the resource, the destructor releases it.

Unique_ptr is exclusive ownership, zero overhead, move-only.

To break shared_ptr cycles, like parent-child observers.

A move constructor steals resources from an rvalue so we copy pointers, not buffers.

The compiler generates a function per type I call it with.

Two bases share a grand-base, so a derived object would get two copies of the grand-base.

A per-class table of function pointers for virtual methods.

Realloc or insert can move elements, so old iterators and pointers dangle.

An anonymous function object.

The basic guarantee leaves the program valid

Virtual enables dynamic dispatch so a base pointer can call the derived override.

unique_ptr and shared_ptr manage lifetime automatically so I rarely call delete.

I mark methods and params const when they should not modify state.

Exclusive ownership of a heap object that deletes on destruction.

Atomic refcount updates add overhead and can bounce cache lines.

It casts to an rvalue so move constructors can steal resources.

In templates it preserves value category when passing arguments onward.

map keeps keys ordered and has stable iterators references more often

Reallocation invalidates all iterators and references.