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Path: utzoo!mnetor!seismo!ll-xn!cit-vax!polecat!fritz
From: fritz@polecat.caltech.edu (Fritz Nordby)
Newsgroups: comp.bugs.sys5
Subject: even more bugs in make
Message-ID: <2888@cit-vax.Caltech.Edu>
Date: Mon, 1-Jun-87 10:57:53 EDT
Article-I.D.: cit-vax.2888
Posted: Mon Jun  1 10:57:53 1987
Date-Received: Wed, 3-Jun-87 00:44:22 EDT
Sender: news@cit-vax.Caltech.Edu
Reply-To: fritz@polecat.Caltech.EDU (Fritz Nordby)
Distribution: world
Organization: California Institute of Technology
Lines: 52
Keywords: IFS, shell script, make
Summary: shell scripts die if IFS is set

I don't know if this has been noticed before, but there is a severe problem
with make and Bourne shell scripts.  If the IFS environment variable is set
when make is invoked, then make resets IFS to an empty string.  This almost
guarantees that Bourne shell scripts will die horribly.

To repeat, create an empty directory, cd there, and do:
% /bin/sh
$ cat >foo <<FOO
echo \$#
set "\$@"
echo \$#
FOO
$ chmod +x foo
$ cat >makefile <<FOO
x:	y
	foo 1 2 3
FOO
$ >y
$ foo 1 2 3
3
3
$ IFS=' 	
'
$ # that's IFS='<space><tab><newline>'
$ export IFS
$ foo 1 2 3
3
3
$ make
	foo 1 2 3
3
1
$ ^D
% 

The final "1" output by foo is the error.  The problem is that the
	set "$@"
in foo is being expanded into
	set "1" "2" "3"
which, since IFS is empty (and therefore there are no field seperators),
is interpreted as
	set "1 2 3"
-- i.e., there is just one argument to set.  Needless to say, this causes
some problems.  For example, suppose /bin/cc is a shell script which invokes
the compiler after adding some flags to the comand line:
	#!/bin/sh
	exec /lib/cc -foo -bar "$@"
If IFS is set when make is invoked, and if make invokes cc, then /lib/cc will
be invoked with argc==2, as if it had been invoked by
	exec /lib/cc "-foo -bar $*"

		Fritz Nordby.	fritz@vlsi.caltech.edu	cit-vax!fritz