Re: an error from the expression: CLS_ISCLASS((Class)receiver) File: sendmsg.c Line 321

[David Chisnall]

On 13 Feb 2009, at 08:30, Truls Becken wrote:

> The other point I'd like to make is that importing <AppKit/AppKit.h>
> in AppController.h would simplify things a bit. I guess it's debatable
> whether this is better than declaring/importing only what is strictly
> needed in the header and then import AppKit in the implementation
> file, like you do now, but generally I think it's simpler to just
> import AppKit in the controller header and be done with it. This would
> replace the 5 classes you currently declare/import - a list which
> would surely grow as you develop you application.

The rationale for not #importing AppKit.h is that it is huge.  The  
preprocessed header is over 700KB (just under 36,000 lines), which  
means that the compiler has to build a parse tree that is likely to be  
several MBs before it even gets to your program.

This is worked around on OS X by using prefix headers.  These are  
preprocessed and pre-parsed headers that are used automatically in  
place of Cocoa.h (which, with GCC, has around a 30MB parse tree).   
This is one of the main reasons why OS X programs use Cocoa.h rather  
than AppKit.h and Foundation.h - you are only allowed one precompiled  
header per program.

I don't know if GNUstep make has support for precompiling Cocoa.h.  If  
not, it might be worth adding, since  it can reduce the memory usage  
and processing time of a big build.

David