Re: CVS commit: src/external/gpl3/autoconf/dist/lib/autoconf

[Luke Mewburn <luke%mewburn.net@localhost>]

I experimented with this, and my analysis of the gnulib emacs regexp
wasn't quite correct.

When I reverted this autoconf change, and fixed m4 as below,
regen works. I'm testing a full build of NetBSD now.


On 23-05-25 06:36, Luke Mewburn wrote:
  | Hi Christos,
  | 
  | Whilst this initially fixed my tools/compat regen problem,
  | I'm not sure it's correct long term.
  | 
  | I think we need to revert this, and fix usr.bin/m4 -g (GNU)
  | emulation for m4 regexp() and patsubst() ?
  | 
  | A quick comparison of usr.bin/m4/gnum4.c twiddle() versus
  |   https://www.gnu.org/software/gnulib/manual/html_node/emacs-regular-expression-syntax.html
  | we may need to make the following changes to twiddle():
  | 1. convert m4 \{ and \} into ERE { and }

This we don't need; gnulib emacs regexp doesn't support { } intervals.


  | 2. convert m4 { and } into ERE \{ and \}

This worked.


  | 3. possibly implement \b, \B, \`, and \'

I haven't done this.


  | 
  | but further analysis and addition of testsuites before & after,
  | comparing behaviour of GNU m4 versus our m4, is probably warranted.
  | 
  | 
  | Details:
  | 
  | autoconf 'm4_bregexp' is GNU m4 1.4.x 'regexp' (well, GNU m4 before 2.x),
  | and 'm4_bpatsubst' is m4 'patsubst'.
  | See:
  | - https://www.gnu.org/software/autoconf/manual/autoconf-2.69/html_node/Redefined-M4-Macros.html
  | 
  | 
  | GNU m4 1.4.x defines 'regexp' as:
  | 	Searches for regexp in string. The syntax for regular expressions is
  | 	the same as in GNU Emacs, which is similar to BRE, Basic Regular
  | 	Expressions in POSIX. See Syntax of Regular Expressions in the GNU
  | 	Emacs Manual.
  | 'patsubst' is similar:
  | 	Searches string for matches of regexp, and substitutes replacement for
  | 	each match. The syntax for regular expressions is the same as in GNU
  | 	Emacs (see Regexp).
  | See:
  | - https://www.gnu.org/software/m4/manual/html_node/Regexp.html
  | - https://www.gnu.org/software/m4/manual/html_node/Patsubst.html
  | 
  | 
  | GNU m4 1.4.x defines 'regexp' as:
  | 	Searches for regexp in string. The syntax for regular expressions is
  | 	the same as in GNU Emacs, which is similar to BRE, Basic Regular
  | 	Expressions in POSIX. See Syntax of Regular Expressions in the GNU
  | 	Emacs Manual.
  | See:
  | - https://www.gnu.org/software/m4/manual/html_node/Regexp.html
  | 
  | 
  | Emacs regexps look to be BREs with extras including \| for alternation.
  | See:
  | - https://www.gnu.org/software/emacs/manual/html_node/emacs/Regexps.html
  | - https://www.gnu.org/software/emacs/manual/html_node/elisp/Regexp-Backslash.html
  | 
  | Note: except that GNU m4 code inspection shows it's uses the gnulib
  | implementation of Emacs regex, which is documented differently to Emacs'
  | own regex! See below.
  | 
  | 
  | GNU m4 uses gnulib for its regexp implementation (per code inspection),
  | and doesn't seem to change the syntax from the gnulib default, which
  | as far as I can tell is Emacs (RE_SYNTAX_EMACS 0. 
  | See:
  | - https://www.gnu.org/software/gnulib/manual/html_node/emacs-regular-expression-syntax.html
  | - https://www.gnu.org/software/gnulib/manual/html_node/Predefined-Syntaxes.html
  | Note that this seems to differ from the Emacs manual above.
  | 
  | 
  | POSIX BREs don't support '|' alternation at all, per NetBSD re_format(7):
  | 	Obsolete (“basic”) regular expressions differ in several respects.
  | 	‘|’ is an ordinary character and there is no equivalent for its
  | 	functionality.
  | and Linux (glibc) regex(7):
  | 	Obsolete ("basic") regular expressions differ in several respects.
  | 	'|', '+', and '?' are ordinary characters and there is no equivalent
  | 	for their functionality.
  | 
  | 
  | It looks like usr.bin/m4's -g (GNU) compatibility option supports
  | rewriting the GNU m4 regexp() and patsubst() expressions to be POSIX ERE.
  | This is done in usr.bin/m4/gnum4.c by the twiddle() function if -g (mimic_gnu)
  | is in operation.
  | 
  | See intro for proposed solution.
  | 
  | 
  | regards,
  | Luke.
  | 
  | 
  | 
  | On 23-05-24 10:34, Christos Zoulas wrote:
  |   | Module Name:	src
  |   | Committed By:	christos
  |   | Date:		Wed May 24 14:34:16 UTC 2023
  |   | 
  |   | Modified Files:
  |   | 	src/external/gpl3/autoconf/dist/lib/autoconf: general.m4
  |   | 
  |   | Log Message:
  |   | quote { to make regcomp happy
  |   | 
  |   | 
  |   | To generate a diff of this commit:
  |   | cvs rdiff -u -r1.1.1.1 -r1.2 \
  |   |     src/external/gpl3/autoconf/dist/lib/autoconf/general.m4
  |   | 
  |   | Please note that diffs are not public domain; they are subject to the
  |   | copyright notices on the relevant files.
  |   | 
  | 
  |   | Modified files:
  |   | 
  |   | Index: src/external/gpl3/autoconf/dist/lib/autoconf/general.m4
  |   | diff -u src/external/gpl3/autoconf/dist/lib/autoconf/general.m4:1.1.1.1 src/external/gpl3/autoconf/dist/lib/autoconf/general.m4:1.2
  |   | --- src/external/gpl3/autoconf/dist/lib/autoconf/general.m4:1.1.1.1	Sat Jan 16 13:36:00 2016
  |   | +++ src/external/gpl3/autoconf/dist/lib/autoconf/general.m4	Wed May 24 10:34:16 2023
  |   | @@ -2119,7 +2119,7 @@ m4_define([AC_DEFINE_UNQUOTED], [_AC_DEF
  |   |  # no backslash, no command substitution, no complex variable
  |   |  # substitution, and no quadrigraphs.
  |   |  m4_define([_AC_DEFINE_UNQUOTED],
  |   | -[m4_if(m4_bregexp([$1], [\\\|`\|\$(\|\${\|@]), [-1],
  |   | +[m4_if(m4_bregexp([$1], [\\\|`\|\$(\|\$\{\|@]), [-1],
  |   |         [AS_ECHO(["AS_ESCAPE([$1], [""])"]) >>confdefs.h],
  |   |         [cat >>confdefs.h <<_ACEOF
  |   |  [$1]
  |   | 
  |