Date: Tue, 6 Oct 2009 22:41:52 +0200 From: Roman Divacky <rdivacky@freebsd.org> To: "Robert N. M. Watson" <rwatson@freebsd.org> 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 Message-ID: <20091006204152.GA37998@freebsd.org> In-Reply-To: <AEEBEAA3-6218-432D-9716-56B0CB84F9E9@freebsd.org> References: <alpine.BSF.2.00.0909271126590.70406@fledge.watson.org> <200910021440.50021.hselasky@freebsd.org> <2097B9F8-B96F-4A37-B1D1-D094D65211F4@mac.com> <AEEBEAA3-6218-432D-9716-56B0CB84F9E9@freebsd.org>
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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. 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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