Re: Kidnapping std::move

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From	"Bo Persson" <bop@gmb.dk>
Subject	Re: Kidnapping std::move
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Rani Sharoni wrote:
> On Jun 30, 7:31 pm, Rani Sharoni <ranisharon...@gmail.com> wrote:
>> I recently encountered an interesting issue in which
>> func(std::move(x)) will actually =93move=94 x even when =91func=92
>> doesn=92=
>
> Sorry for the bad text. This is probably related to pasting from my
> text editor.
> I will try to give a better version of my concern.
>
> Consider the following code:
> struct B {};
> struct D : B {};
>
> set<unique_ptr<B>, ...> aSet;
>
> unique_ptr<B> spB = new D;
> auto res1 = aSet.insert(move(spB));
> assert(res1.second ^ !spB); // take ownership on successful insert
>
> unique_ptr<D> spD = new D;
> auto res2 = aSet.insert(move(spD));
> assert(res2.second ^ !spD); // BUGBUG - spD is always null
> </code>
>

I don't think this is any worse than that the language lets you divide
by zero or index an array out of range.

By using std::move(spD) you say "take it, I don't care about it
anymore". Then on the next line you DO care!


Isn't it a rare condition to try to insert into a set, but still
wanting to keep the duplicate? Why not use a multiset in that case?



Bo Persson



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Kidnapping std::move Rani Sharoni <ranisharoni75@gmail.com> - 2011-06-30 10:31 -0600
  Re: Kidnapping std::move Rani Sharoni <ranisharoni75@gmail.com> - 2011-07-02 01:17 -0600
    Re: Kidnapping std::move Daniel Krügler <daniel.kruegler@googlemail.com> - 2011-07-03 01:39 -0600
      Re: Kidnapping std::move Rani Sharoni <ranisharoni75@gmail.com> - 2011-07-04 09:14 -0600
        Re: Kidnapping std::move Daniel Krügler <daniel.kruegler@googlemail.com> - 2011-07-06 01:16 -0600
    Re: Kidnapping std::move "Bo Persson" <bop@gmb.dk> - 2011-07-04 09:14 -0600
      Re: Kidnapping std::move Rani Sharoni <ranisharoni75@gmail.com> - 2011-07-06 01:15 -0600
    Re: Kidnapping std::move SG <s.gesemann@gmail.com> - 2011-08-18 07:52 -0600

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