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According to Eric Blake on 1/19/2007 7:24 AM:
> According to Ralf Wildenhues on 1/18/2007 10:35 AM:
> [ Can we limit this to, say, the m4-discuss and autoconf lists? ]
Actually, this particular mail can probably stay on just autoconf-patches.
>
>>> Anyways, here are the patches in their current state:
>> Please resubmit without any white-space only changes (e.g., diff -w).
>> It makes evaluating the amount of changes more difficult than necessary.
>
> Coming in a later email; the machine I'm typing this mail on is not where
> I generated the patch.
Here's an updated (and smaller) patch that makes CVS autoconf happy with
branch-1_4 of M4, after today's commit that adds --warn-syntax to M4.
2007-01-27 Eric Blake <ebb9@xxxxxxx>
* lib/m4sugar/m4sugar.m4: Cripple ${1} expansion in M4 2.0 for
portability with 1.4.x behavior.
* doc/autoconf.texi (Quoting and Parameters): New section.
(Quotation and Nested Macros): Touch up example.
* NEWS: Document the new limitation on user macros not exceeding
$9.
* lib/m4sugar/m4sh.m4 (_AS_BOURNE_COMPATIBLE)
(_AS_DETECT_BETTER_SHELL): Avoid failure when using M4 1.4.9's
--warn-syntax option.
* lib/autoconf/programs.m4 (_AC_CHECK_PROG): Likewise.
* lib/autotest/general.m4 (_AT_CREATE_DEBUGGING_SCRIPT):
Likewise.
- --
Don't work too hard, make some time for fun as well!
Eric Blake ebb9@xxxxxxx
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Index: NEWS
===================================================================
RCS file: /sources/autoconf/autoconf/NEWS,v
retrieving revision 1.422
diff -u -p -r1.422 NEWS
--- NEWS 19 Dec 2006 05:41:18 -0000 1.422
+++ NEWS 28 Jan 2007 04:04:51 -0000
@@ -5,6 +5,9 @@
These warnings can be disabled with the new AC_DISABLE_OPTION_CHECKING
macro, or by invoking 'configure' with --disable-option-checking.
+** For portability with the eventual M4 2.0, macros should no longer use
+ anything larger than $9 to refer to arguments.
+
* Major changes in Autoconf 2.61a (2006-12-11)
** AC_FUNC_FSEEKO was broken in 2.61; it didn't make fseeko and ftello visible
Index: doc/autoconf.texi
===================================================================
RCS file: /sources/autoconf/autoconf/doc/autoconf.texi,v
retrieving revision 1.1128
diff -u -p -r1.1128 autoconf.texi
--- doc/autoconf.texi 23 Jan 2007 18:47:23 -0000 1.1128
+++ doc/autoconf.texi 28 Jan 2007 04:04:58 -0000
@@ -434,6 +434,7 @@ M4 Quotation
* Active Characters:: Characters that change the behavior of M4
* One Macro Call:: Quotation and one macro call
+* Quoting and Parameters:: M4 vs. shell parameters
* Quotation and Nested Macros:: Macros calling macros
* Changequote is Evil:: Worse than INTERCAL: M4 + changequote
* Quadrigraphs:: Another way to escape special characters
@@ -8860,10 +8861,6 @@ and their interface might change in the
@cindex M4 quotation
@cindex quotation
-@c FIXME: Grmph, yet another quoting myth: quotation has *never*
-@c prevented `expansion' of $1. Unless it refers to the expansion
-@c of the value of $1? Anyway, we need a rewrite here@enddots{}
-
The most common problem with existing macros is an improper quotation.
This section, which users of Autoconf can skip, but which macro writers
@emph{must} read, first justifies the quotation scheme that was chosen
@@ -8873,6 +8870,7 @@ former helps one to follow the latter.
@menu
* Active Characters:: Characters that change the behavior of M4
* One Macro Call:: Quotation and one macro call
+* Quoting and Parameters:: M4 vs. shell parameters
* Quotation and Nested Macros:: Macros calling macros
* Changequote is Evil:: Worse than INTERCAL: M4 + changequote
* Quadrigraphs:: Another way to escape special characters
@@ -8886,8 +8884,8 @@ To fully understand where proper quotati
to know what the special characters are in Autoconf: @samp{#} introduces
a comment inside which no macro expansion is performed, @samp{,}
separates arguments, @samp{[} and @samp{]} are the quotes themselves,
-and finally @samp{(} and @samp{)} (which M4 tries to match by
-pairs).
+@samp{(} and @samp{)} (which M4 tries to match by pairs), and finally
+@samp{$} inside a macro definition.
In order to understand the delicate case of macro calls, we first have
to present some obvious failures. Below they are ``obvious-ified'',
@@ -9008,10 +9006,73 @@ car([[[a]]])
@result{}[a]
@end example
+@node Quoting and Parameters
+@subsection
+
+When M4 encounters @samp{$} within a macro definition, followed
+immediately by a character it recognizes, it will perform M4 parameter
+expansion. This happens regardless of how many layers of quotes the
+parameter expansion is nested within, or even if it occurs in text that
+will be rescanned as a comment.
+
+@example
+define([none], [$1])
+@result{}
+define([one], [[$1]])
+@result{}
+define([two], [[[$1]]])
+@result{}
+define([comment], [# $1])
+@result{}
+define([active], [ACTIVE])
+@result{}
+none([active])
+@result{}ACTIVE
+one([active])
+@result{}active
+two([active])
+@result{}[active]
+comment([active])
+@result{}# active
+@end example
+
+On the other hand, since autoconf generates shell code, you often want
+to output shell variable expansion, rather than performing M4 parameter
+expansion. To do this, you must use M4 quoting to separate the @samp{$}
+from the next character in the definition of your macro. If the macro
+definition occurs in single-quoted text, then insert another level of
+quoting; if the usage is already inside a double-quoted string, then
+split it into concatenated strings.
+
+@example
+define([single], [one set of quotes for $[]1 in definition])
+@result{}
+define([double], [[two sets of quotes for $][1 in definition]])
+@result{}
+single
+@result{}one set of quotes for $1 in definition
+double
+@result{}two sets of quotes for $1 in definition
+@end example
+
+@acronym{POSIX} states that M4 implementations are free to use
+@samp{$@{} in macro definitions however they like. @acronym{GNU} M4
+1.4.x outputs those two characters literally, whereas @acronym{GNU} M4
+2.0 has an optional extension modeled after shell variable expansion
+semantics. This is in part due to the fact that M4 1.4.x violates
+@acronym{POSIX} by treating @samp{$11} as the eleventh parameter, rather
+than the first parameter concatenated with the string @samp{1}. To
+comply with @acronym{POSIX}, M4 2.0 prefers @samp{$@{11@}} rather than
+@samp{$11} when referring to the eleventh parameter. In Autoconf, the
+M4 2.0 extensions with @samp{$@{} are disabled, so you can safely use
+@samp{$@{1@}} in your macro definitions and have it result in literal
+output, without worrying that M4 will treat it like @samp{$1}. However,
+it does mean that you cannot refer to anything higher than @samp{$9} in
+your macro, if you expect to be portable to both M4 1.4.x and 2.0.
+
With this in mind, we can explore the cases where macros invoke
macros@enddots{}
-
@node Quotation and Nested Macros
@subsection Quotation and Nested Macros
@@ -9105,17 +9166,20 @@ qar([int tab[10];])
@noindent
Ahhh! That's much better.
-But note what you've done: now that the arguments are literal strings,
-if the user wants to use the results of expansions as arguments, she has
-to use an @emph{unquoted} macro call:
+But note what you've done: now that the result of @code{qar} is always
+a literal string, the only time a user can use the results of
+expansions is with an @emph{unquoted} macro call:
@example
qar(active)
@result{}ACT
+qar([active])
+@result{}active
@end example
@noindent
-where she wanted to reproduce what she used to do with @code{car}:
+leaving no way for the user to reproduce what she used to do with
+@code{car}:
@example
car([active])
Index: lib/autoconf/programs.m4
===================================================================
RCS file: /sources/autoconf/autoconf/lib/autoconf/programs.m4,v
retrieving revision 1.65
diff -u -p -r1.65 programs.m4
--- lib/autoconf/programs.m4 23 Jan 2007 18:54:38 -0000 1.65
+++ lib/autoconf/programs.m4 28 Jan 2007 04:04:58 -0000
@@ -2,7 +2,7 @@
# Checking for programs.
# Copyright (C) 1992, 1993, 1994, 1995, 1996, 1998, 1999, 2000, 2001,
-# 2002, 2003, 2004, 2005, 2006 Free Software Foundation, Inc.
+# 2002, 2003, 2004, 2005, 2006, 2007 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
@@ -93,7 +93,7 @@ m4_ifvaln([$6],
# However, it has the same basename, so the bogon will be chosen
# first if we set $1 to just the basename; use the full file name.
shift
- ac_cv_prog_$1="$as_dir/$ac_word${1+' '}$[@]"
+ ac_cv_prog_$1="$as_dir/$ac_word[$]{1+' '}$[@]"
m4_if([$2], [$4],
[ else
# Default is a loser.
Index: lib/autotest/general.m4
===================================================================
RCS file: /sources/autoconf/autoconf/lib/autotest/general.m4,v
retrieving revision 1.218
diff -u -p -r1.218 general.m4
--- lib/autotest/general.m4 25 Nov 2006 09:57:34 -0000 1.218
+++ lib/autotest/general.m4 28 Jan 2007 04:04:58 -0000
@@ -1,8 +1,8 @@
# This file is part of Autoconf. -*- Autoconf -*-
# M4 macros used in building test suites.
-# Copyright (C) 2000, 2001, 2002, 2003, 2004, 2005, 2006 Free Software
-# Foundation, Inc.
+# Copyright (C) 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007 Free
+# Software Foundation, Inc.
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
@@ -169,9 +169,9 @@ m4_define([_AT_NORMALIZE_TEST_GROUP_NUMB
m4_define([_AT_CREATE_DEBUGGING_SCRIPT],
[ {
echo "#! /bin/sh"
- echo 'test "${ZSH_VERSION+set}" = set && alias -g '\''${1+"$[@]"}'\''='\''"$[@]"'\'''
+ echo 'test "${ZSH_VERSION+set}" = set && alias -g '\''[$]{1+"$[@]"}'\''='\''"$[@]"'\'''
AS_ECHO(["cd '$at_dir'"])
- AS_ECHO(["exec \${CONFIG_SHELL-$SHELL} $[0] -v -d $at_debug_args $at_group \${1+\"\$[@]\"}"])
+ AS_ECHO(["exec \${CONFIG_SHELL-$SHELL} $[0] -v -d $at_debug_args $at_group \[$]{1+\"\$[@]\"}"])
echo 'exit 1'
} >$at_group_dir/run
chmod +x $at_group_dir/run
Index: lib/m4sugar/m4sh.m4
===================================================================
RCS file: /sources/autoconf/autoconf/lib/m4sugar/m4sh.m4,v
retrieving revision 1.204
diff -u -p -r1.204 m4sh.m4
--- lib/m4sugar/m4sh.m4 1 Dec 2006 18:32:35 -0000 1.204
+++ lib/m4sugar/m4sh.m4 28 Jan 2007 04:04:59 -0000
@@ -2,7 +2,7 @@
# M4 sugar for common shell constructs.
# Requires GNU M4 and M4sugar.
#
-# Copyright (C) 2000, 2001, 2002, 2003, 2004, 2005, 2006 Free Software
+# Copyright (C) 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007 Free Software
# Foundation, Inc.
#
# This program is free software; you can redistribute it and/or modify
@@ -180,9 +180,9 @@ m4_define([_AS_BOURNE_COMPATIBLE],
[AS_IF([test -n "${ZSH_VERSION+set}" && (emulate sh) >/dev/null 2>&1],
[emulate sh
NULLCMD=:
- [#] Zsh 3.x and 4.x performs word splitting on ${1+"$[@]"}, which
+ [#] Zsh 3.x and 4.x performs word splitting on [$]{1+"$[@]"}, which
# is contrary to our usage. Disable this feature.
- alias -g '${1+"$[@]"}'='"$[@]"'
+ alias -g '[$]{1+"$[@]"}'='"$[@]"'
setopt NO_GLOB_SUBST],
[AS_CASE([`(set -o) 2>/dev/null`], [*posix*], [set -o posix])])
])
@@ -273,7 +273,7 @@ if test "x$CONFIG_SHELL" = x; then
do ($as_unset $as_var) >/dev/null 2>&1 && $as_unset $as_var
done
export CONFIG_SHELL
- exec "$CONFIG_SHELL" "$as_myself" ${1+"$[@]"}])
+ exec "$CONFIG_SHELL" "$as_myself" [$]{1+"$[@]"}])
AS_IF([test $as_have_required = no],
[echo This script requires a shell more modern than all the
Index: lib/m4sugar/m4sugar.m4
===================================================================
RCS file: /sources/autoconf/autoconf/lib/m4sugar/m4sugar.m4,v
retrieving revision 2.100
diff -u -p -r2.100 m4sugar.m4
--- lib/m4sugar/m4sugar.m4 20 Oct 2006 01:34:33 -0000 2.100
+++ lib/m4sugar/m4sugar.m4 28 Jan 2007 04:04:59 -0000
@@ -3,8 +3,8 @@ divert(-1)#
# Base M4 layer.
# Requires GNU M4.
#
-# Copyright (C) 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006 Free Software
-# Foundation, Inc.
+# Copyright (C) 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007 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
@@ -54,6 +54,12 @@ divert(-1)#
# Set the quotes, whatever the current quoting system.
changequote()
changequote([, ])
+# M4 2.0 treats ${1} as an expansion of parameter one, but too many
+# existing autoconf macros expect the 1.4.x behavior of literal output.
+# We can tell the difference by whether the changesyntax builtin exists;
+# this method cripples the 2.0 extension, but does mean that anything
+# higher than $9 cannot be used in macro definitions.
+ifdef([changesyntax], [changesyntax([O+{}])])
# Some old m4's don't support m4exit. But they provide
# equivalent functionality by core dumping because of the
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