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Subject: [boost] Review Request: impl_ptr (pimpl)
From: Vladimir Batov (Vladimir.Batov_at_[hidden])
Date: 2017-08-15 00:51:15

After much procrastination I would like to request a formal review for
the pimpl library... once and for all :-) (given it's been through a few
almost-reviews and discussions)... to get some kind of a resolution one
way or the other. :-)

On one hand it is embarrassingly simple and no match to a string of late
TMP submissions. On the other hand it seems quite handy for ordinary s/w
folk (like me) as it formalizes, streamlines and noticeably simplifies
(IMO) pimpl-based deployments and makes code-review process quite simple
and straightforward. Its benefits are more visible for pimpls with
exclusive-ownership proxy-implementation relationships (value-semantics
pimpls) as it uses internally an incomplete-type management smart
pointer instead of std:unique_ptr.

Given that it is policy-based I am hoping others might get interested
writing additional policies within that framework such as COW or

The major oddity/peculiarity (that caused a stir before and Gavin
mentioned about a year ago) is that the main class -- impl_ptr -- is
declared in the global namespace. That might happen to be a deal breaker
but that's the best I could come up with to get it to work. If anyone
has a better working solution, I am all ears.

That "oddity" is an "implementation detail" and does not affect the user
-- from the user side it appears inside boost. Like boost::impl_ptr...
Internally to address that we might think of striking a compromise. For
ex., instead of the traditional

namespace boost { template<> class impl_ptr }


template<> class _boost_impl_ptr_

Again, that is an implementation nit, wrinkle, niggle (IMO anyway). From
the outside it all looks kosher -- boost::impl_ptr<...> and such.

The code and the docs are at

Due to personal circumstances Glen -- Pimpl's original manager -- had to
bail out. So, if anyone kindly steps forward to manage the review,
that'd be immensely appreciated.

​Thank you,

P.S. Ron, I am only CCing you so that you'd put it to the schedule... Tnx.

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