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Re: M4 syntax $11 vs. ${11}

From: Eric Blake
Subject: Re: M4 syntax $11 vs. ${11}
Date: Wed, 28 Feb 2007 06:45:37 -0700
User-agent: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv: Gecko/20061207 Thunderbird/ Mnenhy/

Hash: SHA1

According to Eric Blake on 2/8/2007 7:52 AM:
> Here's what I'm checking in for 1.4.9.  Anyone who has been testing the
> --warn-syntax option (available only in CVS for a couple of weeks) now
> needs to test with --warn-macro-sequence.  I'm hoping this is the last
> change prior to 1.4.9, but will not release it for a couple of weeks to
> make sure things settle first.
> 2007-02-08  Eric Blake  <address@hidden>
>       Rename --warn-syntax to --warn-macro-sequence[=regex], to make it
>       more flexible, and so that autoconf can use it.

A couple more problems on the branch, found while trying to port this to
CVS head:

2007-02-28  Eric Blake  <address@hidden>

        * src/m4.h (DEFAULT_MACRO_SEQUENCE): Factor out from...
        * src/m4.c (usage): ...here,...
        * src/builtin.c (set_macro_sequence): ...and here.
        (define_user_macro): Fix typo.
        * doc/m4.texinfo (Preprocessor features, Arguments): Fix minor
        (Shift): Document composite macro argn for portably getting at
        positional parameters beyond 9.
        * configure.ac (AC_INIT): Bump version number.
        * NEWS: Start changes of 1.4.8c.

- --
Don't work too hard, make some time for fun as well!

Eric Blake             address@hidden
Version: GnuPG v1.4.5 (Cygwin)
Comment: Public key at home.comcast.net/~ericblake/eblake.gpg
Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org

Index: NEWS
RCS file: /sources/m4/m4/NEWS,v
retrieving revision
diff -u -p -r1. NEWS
--- NEWS        24 Feb 2007 17:32:58 -0000
+++ NEWS        28 Feb 2007 13:41:35 -0000
@@ -2,6 +2,10 @@ GNU M4 NEWS - User visible changes.
 Copyright (C) 1992, 1993, 1994, 2004, 2005, 2006, 2007 Free Software
 Foundation, Inc.
+Version 1.4.9 - ?? ??? 2007, by ???  (CVS version 1.4.8c)
+* Minor documentation and portability cleanups.
 Version 1.4.8b - 24 Feb 2007, by Eric Blake  (CVS version 1.4.8a)
 * Fix a regression introduced in 1.4.8 that made m4 unable to process
Index: configure.ac
RCS file: /sources/m4/m4/configure.ac,v
retrieving revision
diff -u -p -r1.36.2.35 configure.ac
--- configure.ac        24 Feb 2007 17:32:58 -0000
+++ configure.ac        28 Feb 2007 13:41:35 -0000
@@ -18,7 +18,7 @@
 # 02110-1301  USA
-AC_INIT([GNU M4], [1.4.8b], address@hidden)
+AC_INIT([GNU M4], [1.4.8c], address@hidden)
 AM_INIT_AUTOMAKE([1.9.6 dist-bzip2 gnu])
Index: doc/m4.texinfo
RCS file: /sources/m4/m4/doc/m4.texinfo,v
retrieving revision
diff -u -p -r1. m4.texinfo
--- doc/m4.texinfo      24 Feb 2007 14:02:23 -0000
+++ doc/m4.texinfo      28 Feb 2007 13:41:36 -0000
@@ -618,13 +618,12 @@ input came from.  These features occur w
 @table @code
 @item -D @address@hidden@address@hidden
 @itemx address@hidden@address@hidden@r{]}
-This enters @var{NAME} into the symbol table, before any input files are
-read.  If @address@hidden is missing, the value is taken to be the
-empty string.  The @var{VALUE} can be any string, and the macro can be
-defined to take arguments, just as if it was defined from within the
-input.  This option may be given more than once; order with respect to
-file names is significant, and redefining the same @var{NAME} loses the
-previous value.
+This enters @var{NAME} into the symbol table.  If @address@hidden is
+missing, the value is taken to be the empty string.  The @var{VALUE} can
+be any string, and the macro can be defined to take arguments, just as
+if it was defined from within the input.  This option may be given more
+than once; order with respect to file names is significant, and
+redefining the same @var{NAME} loses the previous value.
 @item -I @var{DIRECTORY}
 @itemx address@hidden
@@ -1615,9 +1614,9 @@ consist of one or more digits, allowing 
 arguments.  The extension of accepting multiple digits is incompatible
 with @acronym{POSIX}, and is different than traditional implementations
 of @code{m4}, which only recognize one digit.  Therefore, future
-versions of @acronym{GNU} M4 will phase out this feature.
address@hidden, for an example of how to portably access the eleventh
+versions of @acronym{GNU} M4 will phase out this feature.  To portably
+access beyond the ninth argument, you can use the @code{argn} macro
+documented later (@pxref{Shift}).
 @acronym{POSIX} also states that @samp{$} followed immediately by
 @address@hidden in a macro definition is implementation-defined.  This version
@@ -1645,10 +1644,10 @@ behavior due to the changed behavior of 
 @option{--warn-macro-sequence} command-line option (@pxref{Operation
 modes, , Invoking m4}) with the default regular expression.  This will
 add a warning any time a macro definition includes @samp{$} followed by
-multiple digits, or by @address@hidden and a digit.  The warning is not
-enabled by default, because it triggers a number of warnings in Autoconf
-2.61 (and Autoconf uses @option{-E} to treat warnings as errors), and
-because it will still be possible to restore older behavior in M4 2.0.
+multiple digits, or by @address@hidden  The warning is not enabled by
+default, because it triggers a number of warnings in Autoconf 2.61 (and
+Autoconf uses @option{-E} to treat warnings as errors), and because it
+will still be possible to restore older behavior in M4 2.0.
 @comment ignore
@@ -2439,6 +2438,34 @@ undivert(`quote.m4')dnl
 @end example
address@hidden nine arguments, more than
address@hidden more than nine arguments
address@hidden arguments, more than nine
+One more useful macro based on @code{shift} allows portably selecting
+an arbitrary argument (usually greater than the ninth argument), without
+relying on the @acronym{GNU} extension of multi-digit arguments
address@hidden Composite argn (@var{n}, @dots{})
+Expands to argument @var{n} out of the remaining arguments.  @var{n}
+must be a positive number.  Usually invoked as
address@hidden deffn
+It is implemented as:
+define(`argn', `ifelse(`$1', 1, ``$2'',
+  `argn(decr(`$1'), shift(shift($@@)))')')
+argn(`1', `a')
+define(`foo', `argn(`11', $@@)')
+foo(`a', `b', `c', `d', `e', `f', `g', `h', `i', `j', `k', `l')
address@hidden example
 @node Forloop
 @section Iteration by counting
@@ -5716,6 +5743,9 @@ Eleventh(`a', `b', `c', `d', `e', `f', `
 @end example
+Also see the @code{argn} macro (@pxref{Shift}).
 The @code{divert} (@pxref{Divert}) macro can manage more than 9
 diversions.  @acronym{GNU} @code{m4} treats all positive numbers as valid
Index: src/builtin.c
RCS file: /sources/m4/m4/src/Attic/builtin.c,v
retrieving revision
diff -u -p -r1. builtin.c
--- src/builtin.c       24 Feb 2007 14:02:23 -0000
+++ src/builtin.c       28 Feb 2007 13:41:36 -0000
@@ -253,7 +253,7 @@ set_macro_sequence (const char *regexp)
   const char *msg;
   if (! regexp)
-    regexp = "\\$\\({[^}]*}\\|[0-9][0-9]+\\)";
   else if (regexp[0] == '\0')
       macro_sequence_inuse = false;
@@ -328,7 +328,7 @@ define_user_macro (const char *name, con
       if (offset == -2)
        M4ERROR ((warning_status, 0,
-                 "error checking --warn-define-sequence for macro `%s'",
+                 "error checking --warn-macro-sequence for macro `%s'",
Index: src/m4.c
RCS file: /sources/m4/m4/src/Attic/m4.c,v
retrieving revision
diff -u -p -r1. m4.c
--- src/m4.c    24 Feb 2007 14:02:23 -0000
+++ src/m4.c    28 Feb 2007 13:41:36 -0000
@@ -154,7 +154,7 @@ Operation modes:\n\
       --help                   display this help and exit\n\
       --version                output version information and exit\n\
 ", stdout);
-      fputs ("\
+      printf ("\
   -E, --fatal-warnings         once: warnings become errors, twice: stop\n\
                                execution at first error\n\
   -i, --interactive            unbuffer output, ignore interrupts\n\
@@ -162,8 +162,8 @@ Operation modes:\n\
   -Q, --quiet, --silent        suppress some warnings for builtins\n\
                                warn if macro definition matches REGEXP,\n\
-                               default \\$\\({[^}]*}\\|[0-9][0-9]+\\)\n\
-", stdout);
+                               default %s\n\
       fputs ("\
   -W, --word-regexp=REGEXP     use REGEXP for macro name syntax\n\
Index: src/m4.h
RCS file: /sources/m4/m4/src/m4.h,v
retrieving revision
diff -u -p -r1. m4.h
--- src/m4.h    23 Feb 2007 17:05:27 -0000
+++ src/m4.h    28 Feb 2007 13:41:36 -0000
@@ -407,6 +407,11 @@ typedef struct predefined predefined;
 struct re_pattern_buffer;
 struct re_registers;
+/* The default sequence detects multi-digit parameters (obsolete after
+   1.4.x), and any use of extended arguments with the default ${}
+   syntax (new in 2.0).  */
+#define DEFAULT_MACRO_SEQUENCE "\\$\\({[^}]*}\\|[0-9][0-9]+\\)"
 void builtin_init (void);
 void define_builtin (const char *, const builtin *, symbol_lookup);
 void set_macro_sequence (const char *);

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