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Axter
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 Posted: Tue Apr 18, 2006 8:06 pm Post subject: tr1::shared_ptr and boost::shared_ptr |
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What was the justification for the tr1 shared_ptr not to allow a custom
deleter like the boost::shared_ptr?
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Alf P. Steinbach
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| Posted: Tue Apr 18, 2006 9:06 pm Post subject: Re: tr1::shared_ptr and boost::shared_ptr |
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* Pete Becker:
| Quote: | Axter wrote:
What was the justification for the tr1 shared_ptr not to allow a custom
deleter like the boost::shared_ptr?
There is none. It's part of the TR1 spec.
|
Oops, I didn't notice that.
Is there any hope of having a custom delete function added, as with
boost::shared_ptr?
For example, boost::shared_ptr can be used with a class with protected
or private destructor, without being a friend of that class, by passing
it a deallocation function that does have access to the destructor.
For new code it's presumably no big deal to add friendship for a
standard smart-pointer, but code that relies on the above technique with
boost::smart_ptr won't work by simply replacing with std::shared_ptr
(assuming that's what the TR1 shared_ptr will end up as).
In short, it will require workarounds for all code that now uses
boost::shared_ptr and relies on the custom deleter, when such code is to
be changed to use the standard shared_ptr. And if the class in question
can't be changed (adding friendship), then std::shared_ptr can't be
used. I think it would reflect badly on the standard library if one had
to use boost::shared_ptr /in addition/ to std::shared_ptr.
--
A: Because it messes up the order in which people normally read text.
Q: Why is it such a bad thing?
A: Top-posting.
Q: What is the most annoying thing on usenet and in e-mail?
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Pete Becker
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| Posted: Tue Apr 18, 2006 9:06 pm Post subject: Re: tr1::shared_ptr and boost::shared_ptr |
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Axter wrote:
| Quote: | What was the justification for the tr1 shared_ptr not to allow a custom
deleter like the boost::shared_ptr?
|
There is none. It's part of the TR1 spec.
--
Pete Becker
Roundhouse Consulting, Ltd.
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Alberto Ganesh Barbati
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| Posted: Wed Apr 19, 2006 12:06 am Post subject: Re: tr1::shared_ptr and boost::shared_ptr |
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Pete Becker ha scritto:
| Quote: | Axter wrote:
What was the justification for the tr1 shared_ptr not to allow a custom
deleter like the boost::shared_ptr?
There is none. It's part of the TR1 spec.
|
Uhm? In the latest publicly available draft of TR1 (dated 2005-06-24
http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2005/n1836.pdf)
tr1::shared_ptr definitely *has* support for custom deleters. In
particular, see clause 2.2.3.2. Are you saying that this feature has
been removed in a subsequent (non-publicly available) draft?
Ganesh
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Pete Becker
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| Posted: Wed Apr 19, 2006 4:06 am Post subject: Re: tr1::shared_ptr and boost::shared_ptr |
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Alf P. Steinbach wrote:
| Quote: | * Pete Becker:
Axter wrote:
What was the justification for the tr1 shared_ptr not to allow a custom
deleter like the boost::shared_ptr?
There is none. It's part of the TR1 spec.
Oops, I didn't notice that.
Is there any hope of having a custom delete function added, as with
boost::shared_ptr?
|
Sorry, the earlier "It's part of the TR1 spec" referred to custom
deleters. They're in there.
--
Pete Becker
Roundhouse Consulting, Ltd.
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Howard Hinnant
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| Posted: Wed Apr 19, 2006 4:06 am Post subject: Re: tr1::shared_ptr and boost::shared_ptr |
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In article <4al25bFtp3o9U1 (AT) individual (DOT) net>,
"Alf P. Steinbach" <alfps (AT) start (DOT) no> wrote:
| Quote: | * Pete Becker:
Axter wrote:
What was the justification for the tr1 shared_ptr not to allow a custom
deleter like the boost::shared_ptr?
There is none. It's part of the TR1 spec.
Oops, I didn't notice that.
Is there any hope of having a custom delete function added, as with
boost::shared_ptr?
|
I'm staring at TR1 right now. It says:
template<class T> class shared_ptr {
public:
...
template<class Y, class D> shared_ptr(Y* p, D d);
...
};
Is this not custom deleter support?
Or are we mistakenly talking about custom allocators?
-Howard
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Vaclav Haisman
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| Posted: Wed Apr 19, 2006 4:06 am Post subject: Re: tr1::shared_ptr and boost::shared_ptr |
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Axter wrote:
| Quote: | What was the justification for the tr1 shared_ptr not to allow a custom
deleter like the boost::shared_ptr?
Huh, without custom deleter it would be so much less useful. I find it |
useful for wrapping simple C stuff like FILE* and gdImage* with fclose()
resp. gdImageDestroy() as custom deleter.
--
VH
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Tom Widmer
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| Posted: Wed Apr 19, 2006 3:06 pm Post subject: Re: tr1::shared_ptr and boost::shared_ptr |
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Alberto Ganesh Barbati wrote:
| Quote: | Pete Becker ha scritto:
Axter wrote:
What was the justification for the tr1 shared_ptr not to allow a custom
deleter like the boost::shared_ptr?
There is none. It's part of the TR1 spec.
Uhm? In the latest publicly available draft of TR1 (dated 2005-06-24
http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2005/n1836.pdf)
tr1::shared_ptr definitely *has* support for custom deleters. In
particular, see clause 2.2.3.2. Are you saying that this feature has
been removed in a subsequent (non-publicly available) draft?
|
There seems to be a misunderstanding. As a native english speaker, I
took Pete's comment to meant that:
1. There is no justification for the tr1 shared_ptr not to allow a
custom deleter like the boost::shared_ptr.
2. The custom deleter is part of the tr1::shared_ptr spec.
In other words, the OP asked an invalid question.
Tom
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Pete Becker
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| Posted: Wed Apr 19, 2006 5:06 pm Post subject: Re: tr1::shared_ptr and boost::shared_ptr |
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Alberto Ganesh Barbati wrote:
| Quote: | Pete Becker ha scritto:
Axter wrote:
What was the justification for the tr1 shared_ptr not to allow a custom
deleter like the boost::shared_ptr?
There is none. It's part of the TR1 spec.
Uhm? In the latest publicly available draft of TR1 (dated 2005-06-24
http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2005/n1836.pdf)
tr1::shared_ptr definitely *has* support for custom deleters. In
particular, see clause 2.2.3.2. Are you saying that this feature has
been removed in a subsequent (non-publicly available) draft?
|
No, there's no justification for not allowing it because it is allowed.
--
Pete Becker
Roundhouse Consulting, Ltd.
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Axter
Guest
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| Posted: Thu Apr 20, 2006 4:06 pm Post subject: Re: tr1::shared_ptr and boost::shared_ptr |
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Howard Hinnant wrote:
| Quote: | In article <4al25bFtp3o9U1 (AT) individual (DOT) net>,
"Alf P. Steinbach" <alfps (AT) start (DOT) no> wrote:
* Pete Becker:
Axter wrote:
What was the justification for the tr1 shared_ptr not to allow a custom
deleter like the boost::shared_ptr?
There is none. It's part of the TR1 spec.
Oops, I didn't notice that.
Is there any hope of having a custom delete function added, as with
boost::shared_ptr?
I'm staring at TR1 right now. It says:
template<class T> class shared_ptr {
public:
..
template<class Y, class D> shared_ptr(Y* p, D d);
..
};
Is this not custom deleter support?
Or are we mistakenly talking about custom allocators?
|
I remember previously reading a comparison between TR1::shared_ptr and
boost::shared_ptr, and reading something about tr1::shared_ptr not
having custom deleter.
I just did a google search for the link, but I can't find it now.
Maybe I misread it.
Thanks for the link and correction.
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