[Qt-interest] Const correctness with QSharedPointer

[Thiago Macieira]

Em Terça-feira 08 Dezembro 2009, às 19:11:08, Hostile Fork escreveu:
> > On Mon, Dec 7, 2009 at 4:31 PM, Stephen Jackson <spjackson42 at gmail.com>
> > wrote:
> >
> > I'm going to hijack my own thread here, since I have another question
> > about QSharedPointers.  Is there a way to maintain polymorphism when
> > using QSharedPointers?
> 
> Not too long ago I did a survey of smart pointer variants with respect to
>  this issue (for std::auto_ptr, std::unique_ptr, boost::unique_ptr, and
>  std::tr1::shared_ptr) and you might find it useful:
> 
> 	http://hostilefork.com/2009/07/10/smart-pointer-casting-study/
> 
> I didn't include QSharedPointer because I did not know about it at that
>  time (someone linked me to it after the post).
> 
> But I saw in Thiago's followup that it worked for him.  So I'm not going to
>  try it just now until there's resolution on which compiler + Qt version
>  doesn't do it.  But if that is resolved I'm happy to add a  QSharedPointer
>  example to the article with whatever caveats are appropriate.

The testcase entered our testing system 15 minutes ago (the previous build 
took 15 hours and 22 minutes to finish). We'll know if any of the following 
platforms experience any problems in 12 hours:

- vs2003
- vs2005
- vs2008
- mingw 4.4
- macx cocoa64
- macx cocoa32
- macx carbon
- linux-g++
- qws/linux-g++-x86
- wincewm60 vs2008
- solaris-cc-64
- solaris-g++-64
- symbian 3.2 arm
- symbian 3.2 winscw

The remaining supported platforms will have to wait a little longer (aix-xlc, 
hpuxi-acc, qws-arm, qws-mips, mingw 3.4 and the other Symbian versions).

However, since there are a number of other down-cast tests, I doubt that this 
will be an issue anywhere.

The only issue I currently know of with QSharedPointer is a miscompilation 
with vs2003 in a very particular case. See the QEXPECT_FAIL in 
tst_qsharedpointer.cpp in the Qt sources to see what it is.

-- 
Thiago Macieira - thiago (AT) macieira.info - thiago (AT) kde.org
  Senior Product Manager - Nokia, Qt Development Frameworks
      PGP/GPG: 0x6EF45358; fingerprint:
      E067 918B B660 DBD1 105C  966C 33F5 F005 6EF4 5358
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