Re: [Boost-bugs] [Boost C++ Libraries] #1418: polymorphic archive performance improvement

Subject: Re: [Boost-bugs] [Boost C++ Libraries] #1418: polymorphic archive performance improvement
From: Boost C++ Libraries (noreply_at_[hidden])
Date: 2014-09-13 23:14:18

#1418: polymorphic archive performance improvement
  Reporter: Kim Barrett <kab@…> | Owner: ramey
      Type: Patches | Status: closed
 Milestone: Boost 1.49.0 | Component: serialization
   Version: Boost Release Branch | Severity: Optimization
Resolution: invalid | Keywords: Saitec Eclipse

Comment (by anonymous):

 Replying to [comment:9 ramey]:
> "and then a static (or dynamic when debugging) down-cast to the
 polymorphic-archive class."
> a static downcast from a virtual base is not permitted. see N3797
 paragraph 5.2.9(2)

 Oops. That does potentially kill off that suggested alternative that
 could be used if there were a common base class. But since there isn't
 such a base class, it's pretty much moot anyway, just meaning there may
 not be a reason to add such a base class in order to support this
 alternative implementation. It could be that adding such a base class and
 using a dynamic cast would be an improvement on the current
 implementation. My recollection of my testing way back then indicated
 that it was cross-casts that were very expensive, and down-casts not so
 bad. But that was only with (now) fairly old versions of gcc; newer
 versions of gcc or other compilers might be significantly different.

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