Date: Mon, 23 May 2005 20:50:40 -0600 From: Scott Long <scottl@samsco.org> To: Harti Brandt <harti@freebsd.org> Cc: arch@freebsd.org Subject: Re: Handling of shell builtins in make(1) Message-ID: <42929680.3000309@samsco.org> In-Reply-To: <20050523153118.C28521@beagle.kn.op.dlr.de> References: <20050523153118.C28521@beagle.kn.op.dlr.de>
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Harti Brandt wrote:
>
> Hi all,
>
> I think I found a problem in the shell code in make(1), but I'm not sure
> whether to fix it or not and how. The problem is as follows: in compat
> mode (this is the default mode when make(1) is not called with -j) the
> command lines of a target are executed by one shell per line (this is
> also how Posix wants it). To reduce the number of shells make does an
> optimisation: when the command line does not contain one of a
> pre-defined set of meta characters and does not start with one of a
> predefined set of shell builtins, make directly exec's the command
> instead of using an intermediate shell. The problem is that the current
> list of builtins is limited to:
>
> alias cd eval exec exit read set ulimit unalias umask unset wait
>
> Obviously this is not the full set of shell builtins and does also not
> contain the shell reserved words.
>
> The result of this is that for one and the same command you can get
> different behaviour whether you execute it via make(1) or via sh -c '...'.
> As an example take echo(1). When called via the sh -c you get the builtin
> echo which supports the -e option, when executed by make(1) you get
> /bin/echo which doesn't. If you suddenly include a shell meta character
> in the command line:
>
> foo:
> echo "MAKEFLAGS: ${MAKEFLAGS}"
>
> you suddenly get also the builtin (':' is a meta character).
>
> For the reserved words the situation is almost the same. With the
> following makefile:
>
> foo:
> if
>
> one gets:
>
> if:No such file or directory, while
>
> foo:
> if [ -x /bin/sh ] ; then echo hey ; fi
>
> you get what you expect.
>
> I think all this may be very confusing. The question is what to do. I
> see the following options:
>
> 1. leave it as it is.
>
> 2. include the Posix reserved words and builtins into the list.
>
> 3. include all reserved words and builtins of our shell into the list.
>
> Option (3) is probably best. With (2) you still get different behaviour
> for the two command lines in:
>
> foo:
> bind -h
> bind -h *
>
> (the first line will try to find bind in the path while the second will
> execute the shell builtin).
>
> Opinions?
>
> harti
4. Separate /bin/sh into a front end and back end (libsh) and include
libsh into make.
(running and hiding as I hit the 'send' key)
Scott
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