From: Jani Nikula <jani@nikula.org>
To: Austin Clements <amdragon@MIT.EDU>,
	Vladimir Marek <Vladimir.Marek@Oracle.COM>,
	Notmuch Mail <notmuch@notmuchmail.org>
Subject: Re: [PATCH 4/4] Explicitly type void* pointers
In-Reply-To: <87vcl6nfda.fsf@awakening.csail.mit.edu>
References: <1333966665-10469-1-git-send-email-Vladimir.Marek@oracle.com>
	<1333966665-10469-5-git-send-email-Vladimir.Marek@oracle.com>
	<CAB+hUn_QyMAfC1-Dr23T63ObX=cwuBOzcyCi=61w0MtGRMyt2w@mail.gmail.com>
	<20120409181543.GC10554@pub.czech.sun.com>
	<87mx6ka8y1.fsf@nikula.org>
	<87vcl6nfda.fsf@awakening.csail.mit.edu>
User-Agent: Notmuch/0.11.1+222~ga47a98c (http://notmuchmail.org) Emacs/23.1.1
	(i686-pc-linux-gnu)
Date: Thu, 12 Apr 2012 08:02:12 +0000
Message-ID: <87aa2hxtrv.fsf@nikula.org>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Precedence: list

On Wed, 11 Apr 2012 17:11:13 -0400, Austin Clements <amdragon@MIT.EDU> wrote:
> On Mon, 09 Apr 2012, Jani Nikula <jani@nikula.org> wrote:
> > Vladimir Marek <Vladimir.Marek@Oracle.COM> writes:
> > I'm throwing in a third alternative below. Does it work for you? I think
> > it's both prettier and uglier than the above at the same time! ;)
> >
> > A middle ground would be to change the callers to use
> > "notmuch_talloc_steal", and just #define notmuch_talloc_steal
> > talloc_steal if __GNUC__ >= 3.
> >
> > One could argue upstream talloc should have this, but OTOH it's a C
> > library.
> >
> > BR,
> > Jani.
> >
> >
> > diff --git a/lib/notmuch-private.h b/lib/notmuch-private.h
> > index ea836f7..83b46e8 100644
> > --- a/lib/notmuch-private.h
> > +++ b/lib/notmuch-private.h
> > @@ -499,4 +499,22 @@ _notmuch_filenames_create (const void *ctx,
> >  
> >  NOTMUCH_END_DECLS
> >  
> > +#ifdef __cplusplus
> > +/* Implicit typecast from 'void *' to 'T *' is okay in C, but not in
> > + * C++. In talloc_steal, an explicit cast is provided for type safety
> > + * in some GCC versions. Otherwise, a cast is required. Provide a
> > + * template function for this to maintain type safety, and redefine
> > + * talloc_steal to use it.
> > + */
> > +#if !(__GNUC__ >= 3)
> > +template <class T>
> > +T *notmuch_talloc_steal(const void *new_ctx, const T *ptr)
> > +{
> > +    return static_cast<T*>(talloc_steal(new_ctx, ptr));
> > +}
> > +#undef talloc_steal
> > +#define talloc_steal notmuch_talloc_steal
> > +#endif
> > +#endif
> > +
> >  #endif
> 
> This looks good to me.  I was originally concerned that this depended on
> talloc_steal being a macro, but I realized that's not actually the case.
> Care to roll a real patch?

Sure.

One question: the template must be outside NOTMUCH_{BEGIN,END}_DECLS
(which are just macros for extern "C" block) but should it be within the
#pragma GCC visibility push(hidden) and pop directives? I'm not familiar
with that.

Thanks for the review.


BR,
Jani.