sizeof class with int , function, virtual function in C++?

Question

This is an online C++ test question, which has been done.

#include
using namespace std; 
class A
{

};
class B
{
int i; 
}; 

class C
{
void         


        

Answer 1

why not try printing out the layout? From system V abi

• dsize(O): the data size of an object, which is the size of O without tail padding.
• nvsize(O): the non-virtual size of an object, which is the size of O without virtual bases.
• nvalign(O): the non-virtual alignment of an object, which is the alignment of O without virtual bases.

for example (put your code and remember to apply sizeof to the type you want to check)

struct Base1 {
  virtual int method_base_11() {
    return 11;
  }
  virtual ~Base1() = default;
};

struct Base2 {
  virtual int method_base_21() {
    return 22;
  }
  virtual ~Base2() = default;
};

struct Foo: public Base1, public Base2 {
  int a;
};

int main() {
  Foo foo;
  foo.method_base_21();
  return sizeof(Foo);
}

output,

$ clang -cc1 -std=c++11 -fdump-record-layouts foo.cc

*** Dumping AST Record Layout
         0 | struct Base1
         0 |   (Base1 vtable pointer)
           | [sizeof=8, dsize=8, align=8,
           |  nvsize=8, nvalign=8]

*** Dumping AST Record Layout
         0 | struct Base2
         0 |   (Base2 vtable pointer)
           | [sizeof=8, dsize=8, align=8,
           |  nvsize=8, nvalign=8]

*** Dumping AST Record Layout
         0 | struct Foo
         0 |   struct Base1 (primary base)
         0 |     (Base1 vtable pointer)
         8 |   struct Base2 (base)
         8 |     (Base2 vtable pointer)
        16 |   int a
           | [sizeof=24, dsize=20, align=8,
           |  nvsize=20, nvalign=8]