m4 -g [was: outdated m4sugar]

From 8e6cc3c04610603437d9f67e337d0abf113eb46b Mon Sep 17 00:00:00 2001
From: Eric Blake <[email protected]>
Date: Mon, 14 Jul 2008 06:17:50 -0600
Subject: [PATCH] Add -g/--gnu command line argument.

* src/m4.c (usage): Mention the new option.
(long_options, OPTSTRING): Add new option.
(main): Use it.
* NEWS: Document this addition.
* doc/m4.texinfo (Limits control): Likewise.
(Incompatibilities): Mention future use of POSIXLY_CORRECT.
* THANKS: Update.
Reported by Joel E. Denny.

Signed-off-by: Eric Blake <[email protected]>
---
 ChangeLog      |   12 ++++++++++++
 NEWS           |   12 ++++++++++++
 THANKS         |    1 +
 doc/m4.texinfo |   33 +++++++++++++++++++++++++++++++++
 src/m4.c       |   10 ++++++++--
 5 files changed, 66 insertions(+), 2 deletions(-)

diff --git a/ChangeLog b/ChangeLog
index b32f7b8..45a1db7 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,15 @@
+2008-07-13  Eric Blake  <[email protected]>
+
+	Add -g/--gnu command line argument.
+	* src/m4.c (usage): Mention the new option.
+	(long_options, OPTSTRING): Add new option.
+	(main): Use it.
+	* NEWS: Document this addition.
+	* doc/m4.texinfo (Limits control): Likewise.
+	(Incompatibilities): Mention future use of POSIXLY_CORRECT.
+	* THANKS: Update.
+	Reported by Joel E. Denny.
+
 2008-07-11  Eric Blake  <[email protected]>
 
 	Avoid bogus whitespace in @ovar, @dvar.
diff --git a/NEWS b/NEWS
index bdb7665..1ed9489 100644
--- a/NEWS
+++ b/NEWS
@@ -37,6 +37,18 @@ Foundation, Inc.
    then apply this patch:
      http://git.sv.gnu.org/gitweb/?p=autoconf.git;a=commitdiff;h=56d42fa71
 
+** New `-g'/`--gnu' command-line option overrides `-G'/`--traditional'.
+   For now, the environment variable POSIXLY_CORRECT has no effect on M4
+   behavior; but a future release of M4 will behave as though --traditional
+   is implied if POSIXLY_CORRECT is set (this future change is necessary,
+   because in the current release, there is no way to disable GNU
+   extensions that conflict with POSIX without the use of a non-POSIX
+   command-line argument).  Clients of M4 that want to use GNU extensions,
+   even when POSIXLY_CORRECT is set, should start using the -g command-line
+   argument, even though it is currently a no-op if -G did not appear
+   earlier in the command line, so that the client will not break in the
+   face of an upgraded m4 and a POSIXLY_CORRECT execution environment.
+
 ** The `defn' builtin now warns when operating on an undefined macro name.
    To simulate 1.4.x behavior, use:
      pushdef(`defn', `ifdef(`$1', `builtin(`defn', `$1')')')
diff --git a/THANKS b/THANKS
index 1fa9ba5..6a048b9 100644
--- a/THANKS
+++ b/THANKS
@@ -51,6 +51,7 @@ Jean-Charles Longuet	[email protected]
 Jim Avera		[email protected]
 Jim Kingdom		[email protected]
 Jim Meyering		[email protected]
+Joel E. Denny		[email protected]
 Joel Sherrill		[email protected]
 John Brzustowski	[email protected]
 John David Anglin	[email protected]
diff --git a/doc/m4.texinfo b/doc/m4.texinfo
index d995818..cad75ca 100644
--- a/doc/m4.texinfo
+++ b/doc/m4.texinfo
@@ -744,6 +744,23 @@ only by your hardware and operating system constraints) in @acronym{GNU}
 @code{m4}.
 
 @table @code
+@item -g
+@itemx --gnu
+Enable all the extensions in this implementation.  In this release of
+M4, this option is always on by default; it is currently only useful
+when overriding a prior use of @option{--traditional}.  However, having
+@acronym{GNU} behavior as default makes it impossible to write a
+strictly @acronym{POSIX}-compliant client that avoids all incompatible
+@acronym{GNU} M4 extensions, since such a client would have to use the
+non-@acronym{POSIX} command-line option to force full @acronym{POSIX}
+behavior.  Thus, a future version of M4 will be changed to implicitly
+use the option @option{--traditional} if the environment variable
+@env{POSIXLY_CORRECT} is set.  Projects that intentionally use
+@acronym{GNU} extensions should consider using @option{--gnu} to state
+their intentions, so that the project will not mysteriously break if the
+user upgrades to a newer M4 and has @env{POSIXLY_CORRECT} set in their
+environment.
+
 @item -G
 @itemx --traditional
 Suppress all the extensions made in this implementation, compared to the
@@ -7403,6 +7420,22 @@ However, this appears to be a bug in @acronym{POSIX}, since most
 traditional implementations also ignore all whitespace (formfeed,
 carriage return, and vertical tab).  @acronym{GNU} @code{m4} follows
 tradition and ignores all leading unquoted whitespace.
+
+@item
+@cindex @env{POSIXLY_CORRECT}
+A strictly-compliant @acronym{POSIX} client is not allowed to use
+command-line arguments not specified by @acronym{POSIX}.  However, since
+this version of M4 ignores @env{POSIXLY_CORRECT} and enables the option
+@code{--gnu} by default (@pxref{Limits control, , Invoking m4}), a
+client desiring to be strictly compliant has no way to disable
+@acronym{GNU} extensions that conflict with @acronym{POSIX} when
+directly invoking the compiled @code{m4}.  A future version of
+@code{GNU} M4 will honor the environment variable @env{POSIXLY_CORRECT},
+implicitly enabling @option{--traditional} if it is set, in order to
+allow a strictly-compliant client.  In the meantime, a client needing
+strict @acronym{POSIX} compliance can use the workaround of invoking a
+shell script wrapper, where the wrapper then adds @option{--traditional}
+to the arguments passed to the compiled @code{m4}.
 @end itemize
 
 @node Other Incompatibilities
diff --git a/src/m4.c b/src/m4.c
index 238222f..c73e275 100644
--- a/src/m4.c
+++ b/src/m4.c
@@ -245,6 +245,7 @@ Preprocessor features:\n\
       puts ("");
       fputs (_("\
 Limits control:\n\
+  -g, --gnu                    override -G to re-enable GNU extensions\n\
   -G, --traditional            suppress all GNU extensions\n\
   -H, --hashsize=PRIME         set symbol lookup hash table size [509]\n\
   -L, --nesting-limit=NUMBER   change artificial nesting limit [1024]\n\
@@ -325,6 +326,7 @@ static const struct option long_options[] =
   {"error-output", required_argument, NULL, 'o'}, /* FIXME: deprecate in 2.0 */
   {"fatal-warnings", no_argument, NULL, 'E'},
   {"freeze-state", required_argument, NULL, 'F'},
+  {"gnu", no_argument, NULL, 'g'},
   {"hashsize", required_argument, NULL, 'H'},
   {"include", required_argument, NULL, 'I'},
   {"interactive", no_argument, NULL, 'i'},
@@ -386,9 +388,9 @@ process_file (const char *name)
    '-' forces getopt_long to hand back file names as arguments to opt
    '\1', rather than reordering the command line.  */
 #ifdef ENABLE_CHANGEWORD
-#define OPTSTRING "-B:D:EF:GH:I:L:N:PQR:S:T:U:W:d::eil:o:st:"
+#define OPTSTRING "-B:D:EF:GH:I:L:N:PQR:S:T:U:W:d::egil:o:st:"
 #else
-#define OPTSTRING "-B:D:EF:GH:I:L:N:PQR:S:T:U:d::eil:o:st:"
+#define OPTSTRING "-B:D:EF:GH:I:L:N:PQR:S:T:U:d::egil:o:st:"
 #endif
 
 #ifdef DEBUG_REGEX
@@ -543,6 +545,10 @@ main (int argc, char *const *argv, char *const *envp)
 	interactive = true;
 	break;
 
+      case 'g':
+	no_gnu_extensions = 0;
+	break;
+
       case 'l':
 	{
 	  long tmp = strtol (optarg, NULL, 10);
-- 
1.5.6