Re: classes with pointer data members.

From:

mpho <tjabane@gmail.com>

Newsgroups:

comp.lang.c++.moderated

Date:

Fri, 28 Mar 2008 11:13:01 CST

Message-ID:

<dac54df9-e07c-40df-81c5-8abab5904662@x41g2000hsb.googlegroups.com>

On Mar 17, 4:49 pm, Seungbeom Kim <musip...@bawi.org> wrote:

Ulrich Eckhardt wrote:

I guess you mean something different. When a class contains a handle to a
resource (e.g. a pointer, but also filedescriptor) the compiler-generated
assignment operator will simply copy the handle. This can be okay, but
usually isn't, because it makes the ownership of the resource unclear.

There are several ways out:
1. copy the resource
2. make the class noncopyable
3. share the resource

4. take over the ownership of the resource (as in std::auto_ptr)

Just to make the list more complete.. =)

{ edits quoted signature & clc++m banner removed please don't quote extraneous
material -mod }

Dear all,

To my earlier question in this thread, a (simpler :-) solution that
worked without throwing all sorts of exceptions is:

T& T::operator=(const T& other){

    if (this == &other) return *this;
    else {
          type *p = new type[s] //s -> size of array pointed to by
'pointer'
          std::copy(other.pointer, other.pointer + other.s, p);
          s = other.s;
          delete [] pointer;
          pointer = p;
          //similarly for any other pointers.
    }
    return *this;
}

See "Programming with Exceptions" by Bjarne Stroustrup.
Thanks.

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