Validity of int * array = new int [size]();

Question

int * array = new int [size]();

The operator() allow to set all values of array to 0 (all bits to 0). it's called value-initialization.

Since which version of g++ is it valid?

What about other compilers?

Where can I find it in standard?

Answer 1

This is part of the C++ standard; if it was invalid in g++ then g++ was nonconforming. From the C++ standard (ISO/IEC 14882:2003), several sections are relevant:

5.3.4/15 concerning the new expression says:

If the new-initializer is of the form (), the item is value-initialized

8.5/5 concerning initializers says:

To value-initialize an object of type T means:

— if T is a class type (clause 9) with a user-declared constructor (12.1), then the default constructor for T is called (and the initialization is ill-formed if T has no accessible default constructor);

— if T is a non-union class type without a user-declared constructor, then every non-static data member and base-class component of T is value-initialized;

— if T is an array type, then each element is value-initialized;

— otherwise, the object is zero-initialized

So, for an array of ints, which are a scalar type, the third and fourth bullet points apply.