Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!uwm.edu!uakari.primate.wisc.edu!polyslo!ttwang
From: ttwang@polyslo.CalPoly.EDU (Thomas Wang)
Newsgroups: comp.lang.c++
Subject: order which the constructors are called
Message-ID: <1989Oct18.202605.5971@polyslo.CalPoly.EDU>
Date: 18 Oct 89 20:26:05 GMT
Reply-To: ttwang@polyslo.CalPoly.EDU (Thomas Wang)
Distribution: usa
Organization: Cal Poly State University -- San Luis Obispo
Lines: 38

I have a class with a data member that need to be initialized before all
other data members in that class.

As I seem to recall that the order of constructing data members is undefined,
I wonder if it's still the case?

class student
{
public:
  student(); // 'header' need to be initialized before 'the_foo'
  header_student header;
  bar the_bar;
  foo the_foo;
};

student::student() : header(this), the_foo()
{}

I thought of initializing 'header' in the overloaded 'new' operator, but
that will not work either.  In the case of a stack object, the 'new'
operator will not be called.

If there is no official order of calling the constructors, is there any
'defacto' order of calling the constructors?

Intuitively speaking, I think the order of construction should be
'header', 'the_foo', followed by the unmentioned data member 'the_bar'.

In this case, 'header' contains garbage collection information, so it need
to be initialized before the constructors of other data members allocate
any additional storage space.


 -Thomas Wang ("This is a fantastic comedy that Ataru and his wife Lum, an
                invader from space, cause excitement involving their neighbors."
                  - from a badly translated Urusei Yatsura poster)

                                                     ttwang@polyslo.calpoly.edu