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Date: Mon, 31 Jan 2005 08:30:08 +0100
From: Stepan Kasal <kasal@ucw.cz>
To: autoconf-patches@gnu.org
Cc: cygwin@cygwin.com
Subject: Re: _AS_DETECT_BETTER_SHELL speedup
Message-ID: <20050131073008.GD10602@matsrv.math.cas.cz>
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References: <87k6pydbfw.fsf@penguin.cs.ucla.edu> <20050127174957.GC12120@iam.uni-bonn.de> <87mzuu14oy.fsf@penguin.cs.ucla.edu> <20050128091600.GD13052@matsrv.math.cas.cz> <20050128111251.GA29166@iam.uni-bonn.de> <87sm4lp7pf.fsf@penguin.cs.ucla.edu> <2005-01-29-14-07-53+17789+adl@gnu.org> <20050129134318.GC29209@orchestra.cs.caltech.edu> <2005-01-29-15-03-54+19292+adl@gnu.org> <20050129143419.GB27511@orchestra.cs.caltech.edu>
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Hello,

On Sat, Jan 29, 2005 at 06:34:19AM -0800, Noah Misch wrote:
> On Sat, Jan 29, 2005 at 03:03:53PM +0100, Alexandre Duret-Lutz wrote:
> > $ strace bash -c '{ foo; } 2>/dev/null' 2>&1 | grep clone
> > clone(child_stack=0, flags=CLONE_CHILD_CLEARTID|CLONE_CHILD_SETTID|SIGCHLD, child_tidptr=0xb7f93bc8) = 19138
...
> It indeed turns out that `bash' and the V7 Bourne shell fork in all three cases,
> `ash' and `pdksh' fork only in the first two, and `zsh' forks for none.

I had to use
	$ strace bash -c '{ foo; } 2>/dev/null' 2>&1 | grep fork
with my Linux 2.4.x kernel.

But yes, this proves that "{ ...; }" has no advantage over "(exec ...)".

This also means that we don't need any benchmark from the Cygwin people.
(I apologize to cygwin subscribers.)

Thank you, Alexandr,
	Stepan Kasal

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