Re: Pimpl using auto_ptr

From:
"Alf P. Steinbach" <alfps@start.no>
Newsgroups:
comp.lang.c++
Date:
Thu, 08 Nov 2007 21:35:51 +0100
Message-ID:
<13j6slhjk95ie7a@corp.supernews.com>
* Barry:

Alf P. Steinbach wrote:

Forgot to mention: for that workaround the public class also needs
non-inline constructor, so that the std::auto_ptr is constructed by
the code in the implementation file.


This is not necessary


It is.

struct X;
X* px = 0; // if this is not illformed -- condition1


This is OK.

<code>
#include <memory>

struct Wrapper {
   Wrapper() : sp_(/*0*/) {}
   ~Wrapper();
private:
   struct Impl;
   std::auto_ptr<Impl> sp_;
};

struct Wrapper::Impl {};

Wrapper::~Wrapper() {}

int main()
{
    Wrapper w;
}
</code>


This is not PIMPL. The point of PIMPL is to have the definition of
Wrapper::Impl in a separately compiled file.

if condition1 is true, then the code above is well-formed


See earlier postings for the relevant paragraphs of the standard. The
code above seems to be OK (although it's tricky, and I might be wrong
about that OK). But it's not PIMPL.

Cheers,

- Alf

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