Can you use the sizeof one member when declaring another member?

Question

Is this legal C++?

struct foo
{
  int a[100];
  int b[sizeof(a) / sizeof(a[0])];
};

GCC 4.6 accepts it, but MSVC 2012 doesn\'t. It seems li

Answer 1

This was illegal in C++03 because these members are nonstatic datamembers.

Starting from C++11 this is legal since in an unevaluated operand you can use nonstatic datamembers without having a corresponding object.

Answer 2

Try this: This is a workaround for MSVC 2010 and MSVC 2012

struct Aoo
{
    typedef int ArrayType;
    ArrayType a[100];
};

struct foo : public Aoo
{   
    enum {bSize = sizeof(Aoo) / sizeof(Aoo::ArrayType)};
    int b[bSize];
};