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Date: Tue, 6 Oct 2009 13:35:18 -0700
From: Steve Kargl <sgk@troutmask.apl.washington.edu>
To: "Robert N. M. Watson" <rwatson@freebsd.org>
Message-ID: <20091006203518.GA26478@troutmask.apl.washington.edu>
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	<200910021440.50021.hselasky@freebsd.org>
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Cc: arch@freebsd.org, Chuck Swiger <cswiger@mac.com>,
	Hans Petter Selasky <hselasky@freebsd.org>, freebsd-current@freebsd.org
Subject: Re: [libdispatch-dev] GCD libdispatch w/Blocks support working
	on	Free (f
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On Tue, Oct 06, 2009 at 09:29:50PM +0100, Robert N. M. Watson wrote:
> 
> On 6 Oct 2009, at 19:50, Chuck Swiger wrote:
> 
> >Hi, Hans--
> >
> >On Oct 2, 2009, at 5:40 AM, Hans Petter Selasky wrote:
> >>Can the Apple's "Blocks" C language extension be used when  
> >>programming in the kernel? Or is this a user-space only feature?
> >
> >While the main benefit of blocks is in conjunction with libdispatch  
> >for userland apps, they can be used by themselves, in the kernel or  
> >elsewhere.
> 
> When a block is instantiated (perhaps not the formal terminology), the  
> blocks runtime allocates memory to hold copies of relevant variables  
> from the calling scope. This memory allocation may present an issue in  
> some calling contexts in the kernel -- in particular, it won't be  
> appropriate in contexts were non-sleepable locks are held, interrupt  
> threads, etc. While it should be possible to use the primitive in the  
> kernel, we may want to think carefully about these implications. Also,  
> blocks are currently specific to clang, although with any luck gcc  
> will grow them also.
> 

It is unlikely that gcc will grow support for block any time soon.

http://gcc.gnu.org/ml/gcc/2009-09/msg00272.html

-- 
Steve