Re: Header cleanliness [was: removing the 'make install'-->'makeall'dependency]

[Markus Hitter]

Am Montag, 23.12.02 um 02:25 Uhr schrieb Nicola Pero:

> > > If we get precompiled headers on GNU, that might become the preferred
> > > solution even to cut down compilation time, because usually you will  
> > > have
> > > a precompiled version of Foundation/Foundation.h and of  
> > > AppKit/AppKit.h,
> > > while you will not have precompiled versions of the specific  
> > > Foundation/*,
> > > AppKit/* headers if you include them separately.
> >
> > Why not?
>
> Good point :-)
>
> I don't know enough about precompiled headers to really answer - but I
> heard it's that way on Apple.  Maybe they were too lazy to precompile  
> all
> headers.

From what I've listened in the Apple lists, it seems there is quite  
some dependancy checking to be done when a precompiled header is read  
in. Check for predefined definitions, for file modification dates, for  
equal named files in different places, ...

If you load more than one or two header files, you quickly might waste  
more time with these checks than you save by the precompilation.

Then, it doesn't hurt to load more than you need as long as it goes  
quickly.

At last, the precompiled headers aren't that small. Usually several  
Megs in size.


If somebody wants to try, go to OS X and play with the "fixprecomps"  
script. Currently it makes a precomp for each of the frequent used  
Frameworks/Libraries: AppKit.p, ApplicationServices.p, Carbon.p,  
Cocoa.p, CoreServices.p, Foundation.p, libc.p, mach.p and unistd.p (OK,  
the last two might be an exception).



Cheers,
Markus


P.S.: I've checked some sizes too. Note the differences between the  
three where Cocoa.h includes both, AppKit.h and Foundation.h:
-rw-r--r--  1 root  wheel  3002704 Sep 30 22:09  
/System/Library/Frameworks/Cocoa.framework/Versions/A/Headers/Cocoa- 
gcc3.p
-rw-r--r--  1 root  wheel  2413380 Sep 30 22:08  
/System/Library/Frameworks/Foundation.framework/Versions/C/Headers/ 
Foundation-gcc3.p
-rw-r--r--  1 root  wheel  3002556 Sep 30 22:08  
/System/Library/Frameworks/AppKit.framework/Versions/C/Headers/AppKit- 
gcc3.p

- - - - - - - - - - - - - - - - - - -
Dipl. Ing. Markus Hitter
http://www.jump-ing.de/