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From: Martin Krischik <martin@krischik.com>
Newsgroups: comp.lang.ada
Subject: Re: how can i allocate an objekt with initialization???
Date: Mon, 06 Dec 2004 14:34:13 +0100
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Date: 2004-12-06T14:34:13+01:00
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Adrien Plisson wrote:

> Ole-Hjalmar Kristensen wrote:
> the corresponding C++ example should have been:
> 
> int main(int argc, char *argv[])
> {
>    a &my_object = b(1);

I have seen this before and I am wondering if it is actualy valid. Because:
where is the result of the b(1) constructor call been stored? a& can only
hold a reference to retun value. Is this not a variation on the classic
mistake.

int&
f ()
  {
  auto int retval = 5;

  // do something

  return retval;
  }

and that would mean that the livetime of the constructor call result is
undefined.

>    my_object.f();
> 
>    return 0;
> }
> 

Martin

PS: The above problem case can actually happen to anyone - when hidden by
implicid type convertion

extern int &f(); -- returns valid reference

unsigend&
g ()
  {
  return f();  -- just delegate.
  }

IBM C++ will convert int& to unsigned& - works fine
MS C++ will convert int& to int to unsigned to unsigned& - :-((

-- 
mailto://krischik@users.sourceforge.net
http://www.ada.krischik.com