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#! /bin/sh
# Copyright (C) 2003-2012 Free Software Foundation, Inc.
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 2, or (at your option)
# any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program. If not, see <http://www.gnu.org/licenses/>.
# Check whether double colon rules work. The Unix V7 make manual
# mentions double-colon rules, but POSIX does not. They seem to be
# supported by all Make implementation as far as we can tell. This test
# case is a spy: we want to detect if there exist implementations where
# these do not work. We might use these rules to simplify the rebuild
# rules (instead of the $? hack).
# Tom Tromey write:
# | In the distant past we used :: rules extensively.
# | Fran?ois convinced me to get rid of them:
# |
# | Thu Nov 23 18:02:38 1995 Tom Tromey <tromey@cambric>
# | [ ... ]
# | * subdirs.am: Removed "::" rules
# | * header.am, libraries.am, mans.am, texinfos.am, footer.am:
# | Removed "::" rules
# | * scripts.am, programs.am, libprograms.am: Removed "::" rules
# |
# |
# | I no longer remember the rationale for this. It may have only been a
# | belief that they were unportable.
# On a related topic, the Autoconf manual has the following text:
# | 'VPATH' and double-colon rules
# | Any assignment to 'VPATH' causes Sun 'make' to only execute
# | the first set of double-colon rules. (This comment has been
# | here since 1994 and the context has been lost. It's probably
# | about SunOS 4. If you can reproduce this, please send us a
# | test case for illustration.)
# We already know that overlapping ::-rule like
#
# a :: b
# echo rule1 >> $@
# a :: c
# echo rule2 >> $@
# a :: b c
# echo rule3 >> $@
#
# do not work equally on all platforms. It seems that in all cases
# Make attempts to run all matching rules. However at least GNU Make,
# NetBSD Make, and FreeBSD Make will detect that $@ was updated by the
# first matching rule and skip remaining matches (with the above
# example that means that unless 'a' was declared PHONY, only "rule1"
# will be appended to 'a' if both b and c have changed). Other
# implementations like OSF1 Make and HP-UX Make do not perform such a
# check and execute all matching rules whatever they do ("rule1",
# "rule2", abd "rule3" will all be appended to 'a' if b and c have
# changed).
# So it seems only non-overlapping ::-rule may be portable. This is
# what we check now.
. ./defs || Exit 1
cat >Makefile <<\EOF
a :: b
echo rule1 >> $@
a :: c
echo rule2 >> $@
EOF
touch b c
$sleep
: > a
$MAKE
test "`cat a`" = ''
$sleep
touch b
$MAKE
test "`cat a`" = rule1
# Ensure a is strictly newer than b, so HP-UX make does not execute rule2.
$sleep
: > a
$sleep
touch c
$MAKE
test "`cat a`" = rule2
# Unfortunately, the following is not portable to FreeBSD/NetBSD/OpenBSD
# make, see explanation above.
#: > a
#$sleep
#touch b c
#$MAKE
#grep rule1 a
#grep rule2 a
:
|
