Date: Sat, 14 Feb 2015 21:15:08 +0300 From: Gleb Smirnoff <glebius@FreeBSD.org> To: Bruce Evans <brde@optusnet.com.au> Cc: svn-src-head@freebsd.org, svn-src-all@freebsd.org, src-committers@freebsd.org Subject: Re: svn commit: r278737 - head/usr.sbin/flowctl Message-ID: <20150214181508.GL15484@FreeBSD.org> In-Reply-To: <20150214193210.N945@besplex.bde.org> References: <201502132357.t1DNvKda075915@svn.freebsd.org> <20150214193210.N945@besplex.bde.org>
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Bruce,
On Sat, Feb 14, 2015 at 08:46:58PM +1100, Bruce Evans wrote:
B> Using VLAs and also the C99 feature of declarations anwhere, and extensions
B> like __aligned(), we can almost implement a full alloca() using the fixed
B> version of this change:
B>
B> /*
B> * XXX need extended statement-expression so that __buf doesn't go out
B> * of scope after the right brace.
B> */
B> #define my_alloca(n) __extension__ ({
B> /* XXX need unique name. */ \
B> char __buf[__roundup2((n), MUMBLE)] __aligned(MUMBLE); \
B> \
B> (void *)__buf; \
B> })
I like this idea. But would this exact code work? The life of
__buf is limited by the code block, and we exit the block
immediately. Wouldn't the allocation be overwritten if we
enter any function or block later?
--
Totus tuus, Glebius.
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