Re: linking tool to use a framework : obj_send_msg error

[David Chisnall]

On 13 Apr 2009, at 21:06, Thomas Kupper wrote:

> > On the other hand, if there are only three calls to objc_msgSend in  
> > only one file I could maybe just replace these three calls. But the  
> > objc_msg_lookup calls seems to be quite unusal.
> With "quite unsual" I mean how can I pass the va_list since the  
> objc_msg_lookup only takes two arguments.

You are only passing two arguments to objc_msg_forward().  You are  
passing all of the arguments provided to the macro to the function  
returned by objc_msg_forward().  The __VA_ARGS__ macro is not a  
va_list, it is a special C99 preprocessor token which is exapended to  
the arguments passed to the variadic macro.

This call:

objc_msgSend(obj, sel, arg, arg2);

Will, with the macro I gave you, expand to:

objc_msg_lookup(obj, sel)(obj, sel, arg, arg2);

There are some corner cases where this won't work (i.e. if obj or sel  
is an expression, it will be expanded multiple times - ideally you  
need to assign these to a temporary variable first, but for most cases  
the version I gave you should be adequate).

David