NetNews Offline 2/NetNews Offline Volume 2.iso/news/comp/lang/c++-part1/4399

Internet Message Format | 1996-08-06 | 1.8 KB

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From: John Leonard <[e-mail]>
Newsgroups: comp.lang.c++
Subject: aborting a constructor
Date: Mon, 29 Jan 1996 23:50:51 -0500
Organization: 12th of Nov, Inc
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In an earlier post, I asked how you use 'new' and a constructor in order to deal with the
following situation:
     You have a class, let's call it WindowClass, which, when it is instantiated, does the
following:
     1: It opens the file "filename", and gets its size.
     2: It allocates memory to hold "filename".
     3: It loads "filename" into that memory.
     4: It opens a window to display "filename".
     Now let's suppose that after it performs steps 1 thru 3 it cannot open the window, what does it
do? Furthermore, how do you code for this kind of situation in C++ in general? My first thought was
that the constructor should de-allocate all of the resources that it had received so far. Then it
should throw an exception. The question that I had was: what's going to happen to the memory that
was allocated for the object's data members? I nother words: what happens to an object if its
constructor aborts? Is it automatically deleted? I still haven't really gotten to the bottom of that
question but I want to pose a possible solution to this dilemma and see if it works.
     Instead of the course of action described above, let's say that you have the constructor
execute the following statements:

     delete this;
     throw(error);

and you have the destructor of the class de-allocate the objects. I'd like to know if this would
work.
     John