TITLE: default and no initialization

[ This tip is based on "C/C++ Users Journal" in the article
  "Initializing and Copying Subobjects" by Dan Saks. -adc]

A class can have data members that are classes or of built
in types (int, float, etc). The initialization of data members
is done in the ctor-initializer, which is in turn composed of
a sequence of mem-initializers.

For example,

class Base
{
public:
   Base () : i(10), f(100.0) {}
//           ^^^^^^^^^^^^^^^     ctor-initializer
//           ^^^^^               mem-initializer
//                  ^^^^^^^^     mem-initializer
private:
   int   i;
   float f;
   A     a;
};

Leaving off the initialization for "a" still results in a
call to A's default constructor. However leaving off the
initialization for "i" or "f" is very different. The
constructor for Base might be one of

   Base () : f(100.0) {} 
   Base () : i(), f(100.0) {} 
 
In the first case, "i" will be unitialized. In the second
case, "i" will be initialized with 0 converted to "i's"
type (in this case int). This used to not be the case.

This also applies to heap allocated objects. For example,

	ip = new int;
	ip = new int ();

The former leaves the integer unitialized, the latter initializes
it to 0.