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From: dog@cbnewsl.ATT.COM (edward.n.schiebel)
Newsgroups: comp.lang.c++
Subject: Re: order which the constructors are called
Message-ID: <2349@cbnewsl.ATT.COM>
Date: 19 Oct 89 11:46:42 GMT
References: <1989Oct18.202605.5971@polyslo.CalPoly.EDU>
Distribution: usa
Organization: AT&T Bell Laboratories
Lines: 42

From article <1989Oct18.202605.5971@polyslo.CalPoly.EDU>, by ttwang@polyslo.CalPoly.EDU (Thomas Wang):
> 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?

From the 2.0 Reference Manual, Section 12.6.2

"...First the base classes are initialized in declaration order (
independent of the member-initializers), then the members are initialized
in declaration order (independent of the member-initializers), then the 
body of derived::derived() is executed.  The declaration order is used
to ensure that sub-objects and members are destroyed in the reverse order of initalization.

Virtual base classes constitute a special case..."

but let's not get into that :-)

Thus in your example
> 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()
> {}

The order of initialization is header, the_bar, the_foo.  Note this
is fixed, and is no different even if the constructor were written:

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

	Ed Schiebel
	AT&T Bell Laboratories
	dog@vilya.att.com
	201-386-3416