Re: [Boost-users] Library Interface Design

From: Jeff Flinn (TriumphSprint2000_at_[hidden])
Date: 2006-09-14 22:14:21

"Scott Meyers" <usenet_at_[hidden]> wrote in message 
news:eeakjb$ho0$1_at_sea.gmane.org...

> I'll note that C++ itself allows "uninitialized" objects with
> constructors to be created all the time:
>
>   std::ofstream ofs;

It's funny how this example is the one always chosen by the proponents of 2 
phase construction. Search the newsgroups and you'll find this constructor 
is the root of many problems encountered by users of streams attempting to 
operate on an insufficiently intialized stream object.

>   std::vector<int>::iterator i;

I know, I hate this one too. ;)

>   std::string s;

This is a properly initialized empty string, analogous to an empty vector.

> In each case, there are a few operations that can legitimately be
> performed on such objects, but many operations lead to UB.  Is this
> fundamentally different from the EventLog example?  For example, replace
> EventLog in my example with ofstream, and you have
>
>   std::ofstream ofs;
>   ofs << "Hello World";

What better argument could there be against 2 phase construction?

Jeff Flinn