c++ - Initializing a member array in constructor initializer

Question

class C 
{
public:
 C() : arr({1,2,3}) //doesn't compile
{}
    /*
    C() : arr{1,2,3} //doesn't compile either
{}
    */
private:
 int arr[3];
};

I believe the reason is that arrays can be initialized only with = syntax, that is:

int arr[3] = {1,3,4};

Questions

1. How can I do what I want to do (that is, initialize an array in a constructor (not assigning elements in the body)). Is it even possible?
2. Does the C++03 standard say anything special about initializing aggregates (including arrays) in ctor initializers? Or the invalidness of the above code is a corollary of some other rules?
3. Do C++0x initializer lists solve the problem?

P.S. Please do not mention vectors, boost::arrays, and their superiority to arrays, which I am well aware of.

Answer 1

1. How can I do what I want to do (that is, initialize an array in a constructor (not assigning elements in the body)). Is it even possible?

Yes. It's using a struct that contains an array. You say you already know about that, but then I don't understand the question. That way, you do initialize an array in the constructor, without assignments in the body. This is what boost::array does.

Does the C++03 standard say anything special about initializing aggregates (including arrays) in ctor initializers? Or the invalidness of the above code is a corollary of some other rules?

A mem-initializer uses direct initialization. And the rules of clause 8 forbid this kind of thing. I'm not exactly sure about the following case, but some compilers do allow it.

struct A {
  char foo[6];
  A():foo("hello") { } /* valid? */
};

See this GCC PR for further details.

Do C++0x initializer lists solve the problem?

Yes, they do. However your syntax is invalid, I think. You have to use braces directly to fire off list initialization

struct A {
  int foo[3];
  A():foo{1, 2, 3} { }
  A():foo({1, 2, 3}) { } /* invalid */
};