CODEWITHSUNDEEP
c++c++11
mazatwork
mazatwork

Reputation: 1305

Standard layout and inheritance

What is the reason that the second class is not standard layout? (Visual Studio C++)

#include <iostream>
#include <type_traits>

struct A
{
    int i;
};

struct B : public A
{
};

std::cout << "is_standard_layout<B> == "
          << std::boolalpha
          << std::is_standard_layout<B>::value // gives false
          << std::endl;

Upvotes: 2

Views: 1428

Answers (1)

spraff
spraff

Reputation: 33425

Accorting to this MSVC supports built-in type traits since version 8 but this seems to say that you need version 11.

Section 9.7 defines a standard-layout class as a class that:

  • has no non-static data members of type non-standard-layout class (or array of such types) or reference,
  • has no virtual functions (10.3) and no virtual base classes (10.1),
  • has the same access control (Clause 11) for all non-static data members,
  • has no non-standard-layout base classes,
  • either has no non-static data members in the most derived class and at most one base class with non-static data members, or has no base classes with non-static data members, and
  • has no base classes of the same type as the first non-static data member.

There's some explanation here.

Upvotes: 2

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