On Feb 3, 2011, at 9:38 PM, Greg Parker wrote: > On Feb 3, 2011, at 6:18 PM, Jeff Kelley wrote: >> I’m trying to use objc_msgSend_stret to call -bounds on a UIScreen. I have >> the following code: >> >>> SEL bounds = NSSelectorFromString(@"bounds"); >>> CGRect screenBounds; >>> objc_msgSend_stret((void *)&screenBounds, screen, bounds); >> >> The declaration of objc_msgSend_stret in the Xcode code sense pop-up is as >> follows: >> >>> void objc_msgSend_stret(void * stretAddr, id self, SEL op, ...); >> >> But that’s not what message.h would leave me to believe (with some unrelated >> lines removed): >> >>> #if defined(__OBJC2__) >>> OBJC_EXPORT void objc_msgSend_stret(id self, SEL op, ...); >>> #else >>> /* For compatibility with old objc-runtime.h header */ >>> OBJC_EXPORT void objc_msgSend_stret(void * stretAddr, id self, SEL op, ...); >>> #endif >> >> So, if the declaration is actually the first (I’m compiling for iOS 4.2, so >> I’m pretty sure __OBJC2__ is defined), how do you use it and get the return >> value of the function? > > Both declarations are wrong: you cannot and must not call them directly. The > declaration of objc_msgSend_stret() cannot be expressed in C. > > The correct way to call objc_msgSend_stret() or any other objc_msgSend() > variant is to cast it to an appropriate function pointer type. Like this: > > CGRect (*msgSendFn)(id self, SEL _cmd); > msgSendFn = (CGRect(*)(id, SEL))objc_msgSend_stret; > CGRect screenBounds = msgSendFn(screen, @selector(bounds)); > > If the method had parameters, you would need to add them to the declaration > of the function pointer variable. > > > -- > Greg Parker gpar...@apple.com Runtime Wrangler
That worked like a charm. Thanks, and don’t worry—this isn’t going in shipping code. :) Jeff Kelley slauncha...@gmail.com _______________________________________________ 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: http://lists.apple.com/mailman/options/cocoa-dev/archive%40mail-archive.com This email sent to arch...@mail-archive.com
