[libdispatch-dev] GCD libdispatch w/Blocks support working on Free (f

Roman Divacky rdivacky at freebsd.org
Tue Oct 6 20:42:09 UTC 2009

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.

apple-gcc can do blocks iirc not that it matters for us. judging from the
discussion on gcc ML they dont like this feature (they prefer C++0x lambdas
and the thing from the new C standard iirc)

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