在C++中,几个级别的基类会减慢类/结构吗?

how this works

Herb Sutter

(static_cast<Base*>( this) == this)

http://www.cs.ucsb.edu/~urs/oocsb/papers/oopsla96.pdf

http://keycorner.org/pub/text/doc/kde-slow.txt

http://www.codesourcery.com/public/cxx-abi/cxx-vtable-ex.html

// F is-a E,
// E is-a D and so on

A* aObject = new F(); 
aObject->CallAVirtual();

Corey Ross

dynamic_cast

sturct A { int i; };
struct B { int j; };

struct C : public A, public B { int k ; };

// Let's assume that the layout of C is:  { [ int i ] [ int j ] [int k ] }

void foo (C * c) {
  A * a = c;                // Probably has zero cost
  B * b = c;                // Compiler needed to add sizeof(A) to 'c'
  c = static_cast<B*> (b);  // Compiler needed to take sizeof(A)' from 'b'
}