Calling a method from another method in the same class in C++

What you have should work fine. You can use “this” if you want to:

void A::b() {
  this->a();
  do_stuff;
}

or

void A::b() {
  this->A::a();
  do_stuff;
}

or

void A::b() {
  A::a();
  do_stuff;
}

but what you have should also work:

void A::b() {
  a();
  do_stuff;
}