Re: [boost] [pimpl] Mini Review

Subject: Re: [boost] [pimpl] Mini Review
From: Vladimir Batov (vb.mail.247_at_[hidden])
Date: 2011-05-28 18:12:58

> Gottlob Frege <gottlobfrege <at> gmail.com> writes:
> ...
> I have/had a SBO "DeplorablePimpl" template (see Herb Sutter's
> http://www.gotw.ca/gotw/028.htm).  Basically
> 
> class X {
>     DeplorableImpl<42, XImpl> pimpl;
> };
> 
> It takes care of most/all of Sutter's concerns.  For example, it
> checks at compile time (in the cpp file) that sizeof(XImpl) == 42, (or
> <= 42, depending on policies) and forces correct constructors, etc.
> It does mean that X needs a constructor and destructor to be defined
> in the cpp file, not the h file (since the cpp is where XImpl is
> known, not just declared).
> 
> I'm not sure if this could be incorporated as a policy into a general
> Pimpl, or should be kept somewhat separate.  Maybe just same namespace
> or something.

Oh, yes, I remember this one. :-) I think it might came up during original
few-years-old discussion. Back then I remember I was somewhat apprehensive of
this design. Now that I am growing old, cuddly and agreeable I do feel that this
design has its place... and I dare to say if not prominent then at least an
equal place among others. I do not see anything wrong with an optimization if
the project specifics warrant/demand that. Say, OTOH for short-lived classes
with small XImpl that'd be a *considerable* performance boost. If "my dear"
Pimpl survives, I'll be looking into including it as a policy. 

many thanks,
V.