Re: Quick question on returning references to local variables

From:

Ulrich Eckhardt <eckhardt@satorlaser.com>

Newsgroups:

comp.lang.c++.moderated

Date:

Wed, 22 Jul 2009 12:05:22 CST

Message-ID:

<chrij6-rln.ln1@satorlaser.homedns.org>

ankur wrote:

My question is , in the code below , how is it that the last ob1.show
() displays 15 50, even though the temp object in overloaded operator
function has been destroyed as illustrated by the destructor call.

The code you posted invokes undefined behaviour, so anything is possible,
including "correct" behaviour.

What probably happens is that the memory remained the same, so just looking
at the memory where there once was an object looks like the object. Clobber
the memory in the destructor and you will see that the object was
destroyed.

loc& operator+(loc op2);

Hint: implement operator+ as a free function:

  loc
  operator+(loc const& l1, loc const& l2)
  {
    loc res = l1;
    res += l2;
    return res;
  }

Then, implement operator+= as a memberfunction.

Uli

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