Clang: the thought behind Apple's insistence upon Xcode

François Chaplais francois.chaplais at mines-paristech.fr
Thu Apr 15 17:14:07 EDT 2010


Le 15 avr. 2010 à 21:49, Jerry Daniels a écrit :

> Check this one out:
> 
>     http://www.brockerhoff.net/bb/viewtopic.php?p=2796#2796
> 
> I found this to be a nice meta view of Xcode future and why Apple is drawing the line now. Esoterica is in the post's links. I don't really think this is so much about clipping Adobe's wings, but that is certainly a side effect. 
> 
> Those prone to seeing disaster for revMobile should be of good cheer. There are a couple of foolproof ways to deliver rev coded iPhone and iPad apps that avoid that line that Apple is drawing.
> 
> The webkit may be our savior. One company has already gotten the ok for apps that are made by serving up screens inside a Xcode built client app. The screens are created with JavaScript, HTML5 and CSS. They, of course use the iPhone OS APIs in all their glory. These are much more like app screens than web pages. 
> 
> Best,
> 
> Jerry Daniels
> 

I had noticed the LLVM-Clang thing some time ago. If I understand well, Clang compilers can compile code almost down to machine language-except that it just stops before that. The final step after that is managed elsewhere. The interesting thing thing is that Clang compilers are able to really fine tune your code even though you do not know the processor at this stage.

This is a move by Apple towards independence from chip designers. For instance, I do not know how the G4 iPad chip was designed, but having an "almost" compiler that works independently of the chip must help Apple manage OS X on the iPhone, iPad and Mac.

This may seem like kremlinology, but I think the transition by Apple from PowerPC to x86 was made easier by the fact that OpenStep was designed to be platform (whatever that means) independent. Clearly, SJ likes independence.

Furthermore, it seems that this also related to programming on multicore chips.


There are entries on Clang and LLVM in the english version of wikipedia.

I first heard of this at the Ars Technica review of snow leopard:
http://arstechnica.com/apple/reviews/2009/08/mac-os-x-10-6.ars/9
and later pages
Very nice review, IMHO.

Grand Central Dispatch is also related to Clang and LLVM.
http://arstechnica.com/open-source/news/2009/09/apple-opens-gcd-challenges-impede-adoption-on-linux.ars


Cheers,
	François






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