Le 18 juil. 2012 à 08:28, Rick Mann <rm...@latencyzero.com> a écrit :
> > On Jul 9, 2012, at 16:00 , John McCall wrote: > >>>>> From: Rick Mann <rm...@latencyzero.com> >>>>> Subject: ARC and reinterpret_cast? >>>>> Date: July 7, 2012 9:13:29 PM PDT >>>>> To: Cocoa-Dev List <cocoa-dev@lists.apple.com> >>>>> >>>>> Hi. I'd like to write code like this: >>>>> >>>>> MyObject* foo = reinterpret_cast<__bridge MyObject*> (someVoidPointer); >>>>> >>>>> But the compiler doesn't like it. It's perfectly happy with: >>>>> >>>>> MyObject* foo = (__bridge MyObject) someVoidPointer; >>>>> >>>>> this is in a .mm file. >>>>> >>>>> The error is: >>>>> >>>>> error: type name requires a specifier or qualifier >>>>> MyObject* me = reinterpret_cast<__bridge MyObject*> (inRefCon); >>>>> ^ >>>>> error: expected '>' >>>>> MyObject* me = reinterpret_cast<__bridge MyObject*> (inRefCon); >>>>> ^ >>>>>> >>>>> note: to match this '<' >>>>> MyObject* me = reinterpret_cast<__bridge MyObject*> (inRefCon); >>>>> ^ >>>>> Is it a bug in the compiler, or am I doing something wrong? >> >> Well, it's definitely an ugly error message; that's worth a bug. >> >> The answer is that reinterpret_cast is redundant with __bridge. Bridging >> casts are essentially a different kind of named cast: they document intent >> more precisely than the general cast syntax, and they impose their own >> well-formedness rules about the operand and result type. So you're not >> getting any extra safety here. >> >> This is documented in the ARC specification: >> http://clang.llvm.org/docs/AutomaticReferenceCounting.html#objects.operands.casts >> 3.2.4. Bridged casts >> A bridged cast is a C-style cast annotated with . . . >> >> In theory there's nothing preventing us from allowing these keywords on >> named casts (although it would only be appropriate on reinterpret_cast), >> but our sense is that doing so would only confuse the issue more by >> suggesting subtle differences when none apply. > > Well, more than anything, I wanted to keep consistent casting in my C++ code. > While (__bridge Foo*) might be well-specified, it doesn't look it from the > syntax. Maybe add bridge_cast<Foo*>()? > > Thanks for the clarification, in any case. > Just a though, but isn't it possible to define yourself a template function to do that ? something like template<class C> static inline C bridge_cast(void *ptr) { return (__bridge C)ptr; } -- Jean-Daniel _______________________________________________ Cocoa-dev mailing list (Cocoa-dev@lists.apple.com) Please do not post admin requests or moderator comments to the list. Contact the moderators at cocoa-dev-admins(at)lists.apple.com Help/Unsubscribe/Update your Subscription: https://lists.apple.com/mailman/options/cocoa-dev/archive%40mail-archive.com This email sent to arch...@mail-archive.com
