Change the semantics of AS_EXIT without argument.

* lib/m4sugar/m4sh.m4 (_AS_EXIT_PREPARE): When defaulting, use $?
even if it is 0.
(AS_ERROR): Guarantee non-zero status.
* bin/autoconf.as (exit_missing_arg, getopt): Revert prior change;
we want non-zero status.
* tests/m4sh.at (AS@&t@_EXIT): Update test accordingly.
* doc/autoconf.texi (Common Shell Constructs) <AS_EXIT>: Update
the documentation.
<AS_SET_STATUS>: Don't overly restrict implementation.
(Printing Messages) <AC_MSG_ERROR>: Describe better default.
Suggestions by Paolo Bonzini and Ralf Wildenhues.

Signed-off-by: Eric Blake <ebb9@byu.net>

ChangeLog

@@ -1,3 +1,18 @@
+2008-11-21  Eric Blake  <ebb9@byu.net>
+
+	Change the semantics of AS_EXIT without argument.
+	* lib/m4sugar/m4sh.m4 (_AS_EXIT_PREPARE): When defaulting, use $?
+	even if it is 0.
+	(AS_ERROR): Guarantee non-zero status.
+	* bin/autoconf.as (exit_missing_arg, getopt): Revert prior change;
+	we want non-zero status.
+	* tests/m4sh.at (AS@&t@_EXIT): Update test accordingly.
+	* doc/autoconf.texi (Common Shell Constructs) <AS_EXIT>: Update
+	the documentation.
+	<AS_SET_STATUS>: Don't overly restrict implementation.
+	(Printing Messages) <AC_MSG_ERROR>: Describe better default.
+	Suggestions by Paolo Bonzini and Ralf Wildenhues.
+
 2008-11-21  Eric Blake  <ebb9@byu.net>
 
 	Add @anchors within Builtins and Usual Tools lists.

bin/autoconf.as

@@ -81,7 +81,7 @@ Try \`$as_me --help' for more information."
 exit_missing_arg='
   AS_ECHO(["$as_me: option \`$[1]'\'' requires an argument"]) >&2
   AS_ECHO(["$help"]) >&2
-  AS_EXIT
+  AS_EXIT([1])
 ' # restore font-lock: "
 
 # Variables.
@@ -156,7 +156,7 @@ while test $# -gt 0 ; do
        exec >&2
        AS_ECHO(["$as_me: invalid option $[1]"])
        AS_ECHO(["$help"])
-       AS_EXIT ;;
+       AS_EXIT([1]) ;;
     * )
        break ;;
   esac
@@ -175,7 +175,7 @@ case $# in
       infile=configure.in
     else
       AS_ECHO(["$as_me: no input file"]) >&2
-      AS_EXIT
+      AS_EXIT([1])
     fi
     test -z "$traces" && test -z "$outfile" && outfile=configure;;
   1)
@@ -183,7 +183,7 @@ case $# in
   *) exec >&2
      AS_ECHO(["$as_me: invalid number of arguments."])
      AS_ECHO(["$help"])
-     AS_EXIT ;;
+     AS_EXIT([1]) ;;
 esac
 
 # Unless specified, the output is stdout.

doc/autoconf.texi

@@ -9223,11 +9223,12 @@ This macro prints nothing if @command{configure} is run with the
 @end defmac
 
 @anchor{AC_MSG_ERROR}
-@defmac AC_MSG_ERROR (@var{error-description}, @ovar{exit-status})
+@defmac AC_MSG_ERROR (@var{error-description}, @dvar{exit-status, $?/1})
 @acindex{MSG_ERROR}
 Notify the user of an error that prevents @command{configure} from
 completing.  This macro prints an error message to the standard error
-output and exits @command{configure} with @var{exit-status} (1 by default).
+output and exits @command{configure} with @var{exit-status} (@samp{$?}
+by default, except that @samp{0} is converted to @samp{1}).
 @var{error-description} should be something like @samp{invalid value
 $HOME for \$HOME}.
 
@@ -12165,12 +12166,10 @@ for portability, should not include more than one newline.  The bytes of
 Redirections can be placed outside the macro invocation.
 @end defmac
 
-@defmac AS_EXIT (@dvar{status, max($?/1)})
+@defmac AS_EXIT (@dvar{status, $?})
 @asindex{EXIT}
-Emit code to exit the shell with @var{status}.  If @var{status} is
-omitted, then @samp{$?} is used, except that a status of zero is
-converted to @samp{1}.  To exit with successful status, it is necessary
-to supply an explicit @var{status} that expands to @samp{0}.  This macro
+Emit code to exit the shell with @var{status}, defaulting to @samp{$?}.
+This macro
 works around shells that see the exit status of the command prior to
 @code{exit} inside a @samp{trap 0} handler (@pxref{trap, , Limitations
 of Shell Builtins}).
@@ -12213,9 +12212,10 @@ Also see the @code{AC_PROG_MKDIR_P} macro (@pxref{Particular Programs}).
 
 @defmac AS_SET_STATUS (@var{status})
 @asindex{SET_STATUS}
-Emit shell code to set the value of @samp{$?} to @var{status} without
-forking.  However, this is not guaranteed to abort a shell running with
-@code{set -e} (@pxref{set, , Limitations of Shell Builtins}).
+Emit shell code to set the value of @samp{$?} to @var{status}, as
+efficiently as possible.  However, this is not guaranteed to abort a
+shell running with @code{set -e} (@pxref{set, , Limitations of Shell
+Builtins}).
 @end defmac
 
 @defmac AS_TR_CPP (@var{expression})

lib/m4sugar/m4sh.m4

@@ -539,21 +539,19 @@ m4_defun([_AS_EXIT_PREPARE],
   [AS_FUNCTION_DESCRIBE([as_fn_set_status], [STATUS],
     [Set $? to STATUS, without forking.])], [  return $[]1])]dnl
 [AS_REQUIRE_SHELL_FN([as_fn_exit],
-  [AS_FUNCTION_DESCRIBE([as_fn_exit], [[[STATUS]]],
-    [Exit the shell with STATUS, even in a "trap 0" or "set -e" context.
-     If STATUS is omitted, use the maximum of $? and 1.])],
+  [AS_FUNCTION_DESCRIBE([as_fn_exit], [[[STATUS=$?]]],
+    [Exit the shell with STATUS, even in a "trap 0" or "set -e" context.])],
 [  as_status=$?
   set +e
-  test $as_status = 0 && as_status=1
   as_fn_set_status ${1-$as_status}
   exit ${1-$as_status}])])#_AS_EXIT_PREPARE
 
 
-# AS_EXIT([EXIT-CODE = $?/1])
-# ---------------------------
+# AS_EXIT([EXIT-CODE = $?])
+# -------------------------
 # Exit, with status set to EXIT-CODE in the way that it's seen
 # within "trap 0", and without interference from "set -e".  If
-# EXIT-CODE is omitted, then use $?, except use 1 if $? is 0.
+# EXIT-CODE is omitted, then use $?.
 m4_defun([AS_EXIT],
 [AS_REQUIRE([_AS_EXIT_PREPARE])[]as_fn_exit[]m4_ifval([$1], [ $1])])
 
@@ -769,15 +767,19 @@ _AS_ECHO([$as_me: $1], [$2]);}],
 
 # AS_WARN(PROBLEM)
 # ----------------
+# Output "`basename $0`: WARNING: "STRING to stderr.
 m4_define([AS_WARN],
 [AS_MESSAGE([WARNING: $1], [2])])# AS_WARN
 
 
-# AS_ERROR(ERROR, [EXIT-STATUS = 1])
-# ----------------------------------
+# AS_ERROR(ERROR, [EXIT-STATUS = max($?/1)])
+# ------------------------------------------
+# Output "`basename $0`: error: "STRING to stderr, then exit the
+# script with EXIT-STATUS.
 m4_define([AS_ERROR],
-[{ AS_MESSAGE([error: $1], [2])
-   AS_EXIT([$2]); }])# AS_ERROR
+[{ m4_ifval([$2], [], [as_status=$?; test $as_status -eq 0 && as_status=1
+   ]) AS_MESSAGE([error: $1], [2])
+    AS_EXIT(m4_default([$2], [$as_status])); }])# AS_ERROR
 
 
 

tests/m4sh.at

@@ -308,6 +308,7 @@ test x${1} = xb && AS_EXIT([${2}])
 test x${1} = xc && { AS_SET_STATUS([${2}]); AS_EXIT; }
 test x${1} = xd && trap 's=$?; echo $s; AS_EXIT([$s])' 0
 test x${2} = xe && set -e
+test $[#] -gt 0 || AS_EXIT
 AS_SET_STATUS([3])
 dnl Solaris /bin/sh 'set -e' doesn't react to failed function calls
 test x${2} = xe \
@@ -316,12 +317,13 @@ AS_SET_STATUS([4])
 ]])
 
 AT_CHECK_M4SH
-AT_CHECK([./script], [4])
-AT_CHECK([./script a], [1])
-AT_CHECK([./script b], [1])
+AT_CHECK([./script], [1])
+AT_CHECK([./script ''], [4])
+AT_CHECK([./script a], [0])
+AT_CHECK([./script b], [0])
 AT_CHECK([./script b 0], [0])
 AT_CHECK([./script b 2], [2])
-AT_CHECK([./script c 0], [1])
+AT_CHECK([./script c 0], [0])
 AT_CHECK([./script c 2], [2])
 AT_CHECK([./script d], [4], [[4
 ]])