X-Git-Url: https://git.saurik.com/bison.git/blobdiff_plain/592d0b1eb5a6e8041df3d1461dc9fca60e3e0a54..1168b32295f6acde7a777d9519723fe276155b6b:/data/bison.m4

diff --git a/data/bison.m4 b/data/bison.m4
index cc6a2b90..a5c1ee73 100644
--- a/data/bison.m4
+++ b/data/bison.m4
@@ -1,22 +1,21 @@
                                                             -*- Autoconf -*-
 
 # Language-independent M4 Macros for Bison.
-# Copyright (C) 2002, 2004, 2005, 2006, 2007 Free Software Foundation, Inc.
 
-# This program is free software; you can redistribute it and/or modify
+# Copyright (C) 2002, 2004-2012 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
-# the Free Software Foundation; either version 2 of the License, or
+# the Free Software Foundation, either version 3 of the License, or
 # (at your option) any later version.
-
+#
 # This program is distributed in the hope that it will be useful,
 # but WITHOUT ANY WARRANTY; without even the implied warranty of
 # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 # GNU General Public License for more details.
-
+#
 # You should have received a copy of the GNU General Public License
-# along with this program; if not, write to the Free Software
-# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
-# 02110-1301  USA
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
 
 
 ## ---------------- ##
@@ -32,10 +31,10 @@ b4_comment([$1
 
 m4_text_wrap([Copyright (C) $2 Free Software Foundation, Inc.], [   ])
 
-This program is free software; you can redistribute it and/or modify
+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
-the Free Software Foundation; either version 2, or (at your option)
-any later version.
+the Free Software Foundation, either version 3 of the License, or
+(at your option) any later version.
 
 This program is distributed in the hope that it will be useful,
 but WITHOUT ANY WARRANTY; without even the implied warranty of
@@ -43,9 +42,7 @@ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 GNU General Public License for more details.
 
 You should have received a copy of the GNU General Public License
-along with this program; if not, write to the Free Software
-Foundation, Inc., 51 Franklin Street, Fifth Floor,
-Boston, MA 02110-1301, USA.])
+along with this program.  If not, see <http://www.gnu.org/licenses/>.])
 
 b4_comment([As a special exception, you may create a larger work that contains
 part or all of the Bison parser skeleton and distribute that work
@@ -65,50 +62,76 @@ version 2.2 of Bison.])])
 ## Error handling.  ##
 ## ---------------- ##
 
+# The following error handling macros print error directives that should not
+# become arguments of other macro invocations since they would likely then be
+# mangled.  Thus, they print to stdout directly.
+
+# b4_cat(TEXT)
+# ------------
+# Write TEXT to stdout.  Precede the final newline with an @ so that it's
+# escaped.  For example:
+#
+#   b4_cat([[@complain(invalid input@)]])
+m4_define([b4_cat],
+[m4_syscmd([cat <<'_m4eof'
+]m4_bpatsubst(m4_dquote($1), [_m4eof], [_m4@`eof])[@
+_m4eof
+])dnl
+m4_if(m4_sysval, [0], [], [m4_fatal([$0: cannot write to stdout])])])
+
 # b4_error(KIND, FORMAT, [ARG1], [ARG2], ...)
 # -------------------------------------------
-# Write @KIND(FORMAT@,ARG1@,ARG2@,...@) to diversion 0.
+# Write @KIND(FORMAT@,ARG1@,ARG2@,...@) to stdout.
+#
+# For example:
+#
+#   b4_error([[warn]], [[invalid value for '%s': %s]], [[foo]], [[3]])
 m4_define([b4_error],
-[m4_divert_push(0)[@]$1[(]$2[]m4_if([$#], [2], [],
-[m4_foreach([b4_arg],
-            m4_dquote(m4_shift(m4_shift($@))),
-            [[@,]b4_arg])])[@)]m4_divert_pop(0)])
+[b4_cat([[@]$1[(]$2[]]dnl
+[m4_if([$#], [2], [],
+       [m4_foreach([b4_arg],
+                   m4_dquote(m4_shift(m4_shift($@))),
+                   [[@,]b4_arg])])[@)]])])
 
 # b4_error_at(KIND, START, END, FORMAT, [ARG1], [ARG2], ...)
 # ----------------------------------------------------------
-# Write @KIND(START@,END@,FORMAT@,ARG1@,ARG2@,...@) to diversion 0.
+# Write @KIND_at(START@,END@,FORMAT@,ARG1@,ARG2@,...@) to stdout.
+#
+# For example:
+#
+#   b4_error_at([[complain]], [[input.y:2.3]], [[input.y:5.4]],
+#               [[invalid %s]], [[foo]])
 m4_define([b4_error_at],
-[m4_divert_push(0)[@]$1[_at(]$2[@,]$3[@,]$4[]m4_if([$#], [4], [],
-[m4_foreach([b4_arg],
-            m4_dquote(m4_shift(m4_shift(m4_shift(m4_shift($@))))),
-            [[@,]b4_arg])])[@)]m4_divert_pop(0)])
+[b4_cat([[@]$1[_at(]$2[@,]$3[@,]$4[]]dnl
+[m4_if([$#], [4], [],
+       [m4_foreach([b4_arg],
+                   m4_dquote(m4_shift(m4_shift(m4_shift(m4_shift($@))))),
+                   [[@,]b4_arg])])[@)]])])
 
 # b4_warn(FORMAT, [ARG1], [ARG2], ...)
 # ------------------------------------
-# Write @warn(FORMAT@,ARG1@,ARG2@,...@) to diversion 0.
+# Write @warn(FORMAT@,ARG1@,ARG2@,...@) to stdout.
+#
+# For example:
+#
+#   b4_warn([[invalid value for '%s': %s]], [[foo]], [[3]])
 #
 # As a simple test suite, this:
 #
+#   m4_divert(-1)
 #   m4_define([asdf], [ASDF])
 #   m4_define([fsa], [FSA])
 #   m4_define([fdsa], [FDSA])
 #   b4_warn([[[asdf), asdf]]], [[[fsa), fsa]]], [[[fdsa), fdsa]]])
-#   m4_divert(0)
 #   b4_warn([[asdf), asdf]], [[fsa), fsa]], [[fdsa), fdsa]])
-#   m4_divert(0)
-#   b4_warn([asdf), asdf], [fsa), fsa], [fdsa), fdsa])
-#   m4_divert(0)
 #   b4_warn()
-#   m4_divert(0)
 #   b4_warn(1)
-#   m4_divert(0)
 #   b4_warn(1, 2)
 #
-# Should produce this:
+# Should produce this without newlines:
 #
 #   @warn([asdf), asdf]@,[fsa), fsa]@,[fdsa), fdsa]@)
 #   @warn(asdf), asdf@,fsa), fsa@,fdsa), fdsa@)
-#   @warn(ASDF), ASDF@,FSA), FSA@,FDSA), FDSA@)
 #   @warn(@)
 #   @warn(1@)
 #   @warn(1@,2@)
@@ -117,37 +140,47 @@ m4_define([b4_warn],
 
 # b4_warn_at(START, END, FORMAT, [ARG1], [ARG2], ...)
 # ---------------------------------------------------
-# Write @warn(START@,END@,FORMAT@,ARG1@,ARG2@,...@) to diversion 0.
+# Write @warn(START@,END@,FORMAT@,ARG1@,ARG2@,...@) to stdout.
+#
+# For example:
+#
+#   b4_warn_at([[input.y:2.3]], [[input.y:5.4]], [[invalid %s]], [[foo]])
 m4_define([b4_warn_at],
 [b4_error_at([[warn]], $@)])
 
 # b4_complain(FORMAT, [ARG1], [ARG2], ...)
 # ----------------------------------------
-# Write @complain(FORMAT@,ARG1@,ARG2@,...@) to diversion 0.
+# Write @complain(FORMAT@,ARG1@,ARG2@,...@) to stdout.
 #
-# See the test suite for b4_warn above.
+# See b4_warn example.
 m4_define([b4_complain],
 [b4_error([[complain]], $@)])
 
 # b4_complain_at(START, END, FORMAT, [ARG1], [ARG2], ...)
 # -------------------------------------------------------
-# Write @complain(START@,END@,FORMAT@,ARG1@,ARG2@,...@) to diversion 0.
+# Write @complain(START@,END@,FORMAT@,ARG1@,ARG2@,...@) to stdout.
+#
+# See b4_warn_at example.
 m4_define([b4_complain_at],
 [b4_error_at([[complain]], $@)])
 
 # b4_fatal(FORMAT, [ARG1], [ARG2], ...)
 # -------------------------------------
-# Write @fatal(FORMAT@,ARG1@,ARG2@,...@) to diversion 0.
+# Write @fatal(FORMAT@,ARG1@,ARG2@,...@) to stdout and exit.
 #
-# See the test suite for b4_warn above.
+# See b4_warn example.
 m4_define([b4_fatal],
-[b4_error([[fatal]], $@)])
+[b4_error([[fatal]], $@)dnl
+m4_exit(1)])
 
 # b4_fatal_at(START, END, FORMAT, [ARG1], [ARG2], ...)
 # ----------------------------------------------------
-# Write @fatal(START@,END@,FORMAT@,ARG1@,ARG2@,...@) to diversion 0.
+# Write @fatal(START@,END@,FORMAT@,ARG1@,ARG2@,...@) to stdout and exit.
+#
+# See b4_warn_at example.
 m4_define([b4_fatal_at],
-[b4_error_at([[fatal]], $@)])
+[b4_error_at([[fatal]], $@)dnl
+m4_exit(1)])
 
 
 ## ---------------- ##
@@ -200,9 +233,9 @@ m4_define([b4_define_flag_if],
 
 # _b4_define_flag_if($1, $2, FLAG)
 # --------------------------------
-# This macro works around the impossibility to define macros
-# inside macros, because issuing `[$1]' is not possible in M4 :(.
-# This sucks hard, GNU M4 should really provide M5 like $$1.
+# Work around the impossibility to define macros inside macros,
+# because issuing `[$1]' is not possible in M4.  GNU M4 should provide
+# $$1 a la M5/TeX.
 m4_define([_b4_define_flag_if],
 [m4_if([$1$2], $[1]$[2], [],
        [m4_fatal([$0: Invalid arguments: $@])])dnl
@@ -213,19 +246,16 @@ m4_define([b4_$3_if],
 # b4_FLAG_if(IF-TRUE, IF-FALSE)
 # -----------------------------
 # Expand IF-TRUE, if FLAG is true, IF-FALSE otherwise.
-b4_define_flag_if([defines])	        # Whether headers are requested.
-b4_define_flag_if([error_verbose])	# Whether error are verbose.
-b4_define_flag_if([glr])		# Whether a GLR parser is requested.
-b4_define_flag_if([locations])	        # Whether locations are tracked.
-b4_define_flag_if([nondeterministic])	# Whether conflicts should be handled.
-b4_define_flag_if([pull])	        # Whether pull parsing is requested.
-b4_define_flag_if([pure])	        # Whether the interface is pure.
-b4_define_flag_if([push])	        # Whether push parsing is requested.
-b4_define_flag_if([use_push_for_pull])  # Whether push parsing should be used
-                                        # in place of pull parsing (where
-                                        # available) for the sake of the test
-                                        # suite.
-b4_define_flag_if([yacc])	        # Whether POSIX Yacc is emulated.
+b4_define_flag_if([defines])            # Whether headers are requested.
+b4_define_flag_if([error_verbose])      # Whether error are verbose.
+b4_define_flag_if([glr])                # Whether a GLR parser is requested.
+b4_define_flag_if([locations])          # Whether locations are tracked.
+b4_define_flag_if([nondeterministic])   # Whether conflicts should be handled.
+b4_define_flag_if([token_table])        # Whether yytoken_table is demanded.
+b4_define_flag_if([yacc])               # Whether POSIX Yacc is emulated.
+
+# yytoken_table is needed to support verbose errors.
+b4_error_verbose_if([m4_define([b4_token_table_flag], [1])])
 
 
 ## ------------------------- ##
@@ -285,14 +315,14 @@ b4_define_user_code([pre_prologue])
 b4_define_user_code([stype])
 
 
-# b4_check_user_names(WHAT, USER-LIST, SKELETON-NAMESPACE)
-# --------------------------------------------------------
-# Warn if any name of type WHAT is used by the user (as recorded in USER-LIST)
-# but is not used by the skeleton (as recorded by macros in the namespace
-# SKELETON-NAMESPACE).
+# b4_check_user_names(WHAT, USER-LIST, BISON-NAMESPACE)
+# -----------------------------------------------------
+# Complain if any name of type WHAT is used by the user (as recorded in
+# USER-LIST) but is not used by Bison (as recorded by macros in the
+# namespace BISON-NAMESPACE).
 #
-# USER-LIST must expand to a list specifying all grammar occurrences of all
-# names of type WHAT.   Each item in the list must be a triplet specifying one
+# USER-LIST must expand to a list specifying all user occurrences of all names
+# of type WHAT.   Each item in the list must be a triplet specifying one
 # occurrence: name, start boundary, and end boundary.  Empty string names are
 # fine.  An empty list is fine.
 #
@@ -304,22 +334,22 @@ b4_define_user_code([stype])
 #               [[[[bar]], [[parser.y:5.7]], [[parser.y:5.16]]]],
 #               [[[[baz]], [[parser.y:8.7]], [[parser.y:8.16]]]]]])
 #
-# The macro SKELETON-NAMESPACE(bar) must be defined iff the name bar of type
-# WHAT is used in the skeleton.  Empty string names are fine, but it would be
-# ugly for a Bison skeleton to actually use one.
+# The macro BISON-NAMESPACE(bar) must be defined iff the name bar of type WHAT
+# is used by Bison (in the front-end or in the skeleton).  Empty string names
+# are fine, but it would be ugly for Bison to actually use one.
 #
-# For example, to use b4_foo_skeleton_names for SKELETON-NAMESPACE and define
-# that the names bar and baz are used in the skeleton:
+# For example, to use b4_foo_bison_names for BISON-NAMESPACE and define that
+# the names bar and baz are used by Bison:
 #
-#   m4_define([b4_foo_skeleton_names(bar)])
-#   m4_define([b4_foo_skeleton_names(baz)])
+#   m4_define([b4_foo_bison_names(bar)])
+#   m4_define([b4_foo_bison_names(baz)])
 #
 # To invoke b4_check_user_names with TYPE foo, with USER-LIST
-# b4_foo_user_names, with SKELETON-NAMESPACE b4_foo_skeleton_names, and with
-# correct quoting:
+# b4_foo_user_names, with BISON-NAMESPACE b4_foo_bison_names, and with correct
+# quoting:
 #
 #   b4_check_user_names([[foo]], [b4_foo_user_names],
-#                       [[b4_foo_skeleton_names]])
+#                       [[b4_foo_bison_names]])
 m4_define([b4_check_user_names],
 [m4_foreach([b4_occurrence], $2,
 [m4_pushdef([b4_occurrence], b4_occurrence)dnl
@@ -327,70 +357,186 @@ m4_pushdef([b4_user_name], m4_car(b4_occurrence))dnl
 m4_pushdef([b4_start], m4_car(m4_shift(b4_occurrence)))dnl
 m4_pushdef([b4_end], m4_shift(m4_shift(b4_occurrence)))dnl
 m4_ifndef($3[(]m4_quote(b4_user_name)[)],
-          [b4_warn_at([b4_start], [b4_end],
-                      [[%s `%s' is not used]],
-                      [$1], [b4_user_name])])[]dnl
+          [b4_complain_at([b4_start], [b4_end],
+                          [[%s '%s' is not used]],
+                          [$1], [b4_user_name])])[]dnl
 m4_popdef([b4_occurrence])dnl
 m4_popdef([b4_user_name])dnl
 m4_popdef([b4_start])dnl
 m4_popdef([b4_end])dnl
 ])])
 
-# b4_percent_define_get(VARIABLE)
+
+
+
+## --------------------- ##
+## b4_percent_define_*.  ##
+## --------------------- ##
+
+
+# b4_percent_define_use(VARIABLE)
 # -------------------------------
-# If the %define variable VARIABLE is defined, emit its value.  Also, record
-# the skeleton's usage of VARIABLE by defining
-# b4_percent_define_skeleton_variables(VARIABLE).
+# Declare that VARIABLE was used.
+m4_define([b4_percent_define_use],
+[m4_define([b4_percent_define_bison_variables(]$1[)])dnl
+])
+
+# b4_percent_define_get(VARIABLE, [DEFAULT])
+# ------------------------------------------
+# Mimic muscle_percent_define_get in ../src/muscle-tab.h.  That is, if
+# the %define variable VARIABLE is defined, emit its value.  Contrary
+# to its C counterpart, return DEFAULT otherwise.  Also, record
+# Bison's usage of VARIABLE by defining
+# b4_percent_define_bison_variables(VARIABLE).
 #
 # For example:
 #
 #   b4_percent_define_get([[foo]])
 m4_define([b4_percent_define_get],
-[m4_define([b4_percent_define_skeleton_variables(]$1[)])dnl
-m4_ifdef([b4_percent_define(]$1[)], [m4_indir([b4_percent_define(]$1[)])])])
+[b4_percent_define_use([$1])dnl
+m4_ifdef([b4_percent_define(]$1[)],
+         [m4_indir([b4_percent_define(]$1[)])],
+         [$2])])
+
+
+# b4_percent_define_get_loc(VARIABLE)
+# -----------------------------------
+# Mimic muscle_percent_define_get_loc in ../src/muscle-tab.h exactly.  That is,
+# if the %define variable VARIABLE is undefined, complain fatally since that's
+# a Bison or skeleton error.  Otherwise, return its definition location in a
+# form approriate for the first two arguments of b4_warn_at, b4_complain_at, or
+# b4_fatal_at.  Don't record this as a Bison usage of VARIABLE as there's no
+# reason to suspect that the user-supplied value has yet influenced the output.
+#
+# For example:
+#
+#   b4_complain_at(b4_percent_define_get_loc([[foo]]), [[invalid foo]])
+m4_define([b4_percent_define_get_loc],
+[m4_ifdef([b4_percent_define_loc(]$1[)],
+          [m4_pushdef([b4_loc], m4_indir([b4_percent_define_loc(]$1[)]))dnl
+b4_loc[]dnl
+m4_popdef([b4_loc])],
+          [b4_fatal([[b4_percent_define_get_loc: undefined %%define variable '%s']], [$1])])])
+
+# b4_percent_define_get_syncline(VARIABLE)
+# ----------------------------------------
+# Mimic muscle_percent_define_get_syncline in ../src/muscle-tab.h exactly.
+# That is, if the %define variable VARIABLE is undefined, complain fatally
+# since that's a Bison or skeleton error.  Otherwise, return its definition
+# location as a b4_syncline invocation.  Don't record this as a Bison usage of
+# VARIABLE as there's no reason to suspect that the user-supplied value has yet
+# influenced the output.
+#
+# For example:
+#
+#   b4_percent_define_get_syncline([[foo]])
+m4_define([b4_percent_define_get_syncline],
+[m4_ifdef([b4_percent_define_syncline(]$1[)],
+          [m4_indir([b4_percent_define_syncline(]$1[)])],
+          [b4_fatal([[b4_percent_define_get_syncline: undefined %%define variable '%s']], [$1])])])
 
 # b4_percent_define_ifdef(VARIABLE, IF-TRUE, [IF-FALSE])
 # ------------------------------------------------------
-# If the %define variable VARIABLE is defined, expand IF-TRUE, else expand
-# IF-FALSE.  Also, record the skeleton's usage of VARIABLE by defining
-# b4_percent_define_skeleton_variables(VARIABLE).
+# Mimic muscle_percent_define_ifdef in ../src/muscle-tab.h exactly.  That is,
+# if the %define variable VARIABLE is defined, expand IF-TRUE, else expand
+# IF-FALSE.  Also, record Bison's usage of VARIABLE by defining
+# b4_percent_define_bison_variables(VARIABLE).
+#
+# For example:
+#
+#   b4_percent_define_ifdef([[foo]], [[it's defined]], [[it's undefined]])
 m4_define([b4_percent_define_ifdef],
 [m4_ifdef([b4_percent_define(]$1[)],
-	  [m4_define([b4_percent_define_skeleton_variables(]$1[)])$2],
+	  [m4_define([b4_percent_define_bison_variables(]$1[)])$2],
 	  [$3])])
 
 # b4_percent_define_flag_if(VARIABLE, IF-TRUE, [IF-FALSE])
 # --------------------------------------------------------
-# If the %define variable VARIABLE is defined to anything but "0" or "false",
-# expand IF-TRUE. If it is defined to "0" or "false", expand IF-FALSE.  If
-# it is undefined, raise an error (this macro should be preceded by
-# b4_percent_define_default).  Also, record the skeleton's usage of VARIABLE by
-# defining b4_percent_define_skeleton_variables(VARIABLE).
+# Mimic muscle_percent_define_flag_if in ../src/muscle-tab.h exactly.  That is,
+# if the %define variable VARIABLE is defined to "" or "true", expand IF-TRUE.
+# If it is defined to "false", expand IF-FALSE.  Complain if it is undefined
+# (a Bison or skeleton error since the default value should have been set
+# already) or defined to any other value (possibly a user error).  Also, record
+# Bison's usage of VARIABLE by defining
+# b4_percent_define_bison_variables(VARIABLE).
+#
+# For example:
+#
+#   b4_percent_define_flag_if([[foo]], [[it's true]], [[it's false]])
 m4_define([b4_percent_define_flag_if],
 [b4_percent_define_ifdef([$1],
-			 [m4_case(b4_percent_define_get([$1]),
-			          [0], [$3], [false], [$3],
-				  [$2])],
-		         [m4_fatal([invalid %define variable passed to b4_percent_define_flag_if: ]$1)])])
+  [m4_case(b4_percent_define_get([$1]),
+           [], [$2], [true], [$2], [false], [$3],
+           [m4_expand_once([b4_complain_at(b4_percent_define_get_loc([$1]),
+                                           [[invalid value for %%define Boolean variable '%s']],
+                                           [$1])],
+                           [[b4_percent_define_flag_if($1)]])])],
+  [b4_fatal([[b4_percent_define_flag_if: undefined %%define variable '%s']], [$1])])])
 
 # b4_percent_define_default(VARIABLE, DEFAULT)
 # --------------------------------------------
-# If the %define variable VARIABLE is undefined, set its value to DEFAULT.
+# Mimic muscle_percent_define_default in ../src/muscle-tab.h exactly.  That is,
+# if the %define variable VARIABLE is undefined, set its value to DEFAULT.
+# Don't record this as a Bison usage of VARIABLE as there's no reason to
+# suspect that the value has yet influenced the output.
 #
 # For example:
 #
 #   b4_percent_define_default([[foo]], [[default value]])
 m4_define([b4_percent_define_default],
 [m4_ifndef([b4_percent_define(]$1[)],
-           [m4_define([b4_percent_define(]$1[)], [$2])])])
+           [m4_define([b4_percent_define(]$1[)], [$2])dnl
+            m4_define([b4_percent_define_loc(]$1[)],
+                      [[[[<skeleton default value>:-1.-1]],
+                        [[<skeleton default value>:-1.-1]]]])dnl
+            m4_define([b4_percent_define_syncline(]$1[)], [[]])])])
+
+# b4_percent_define_check_values(VALUES)
+# --------------------------------------
+# Mimic muscle_percent_define_check_values in ../src/muscle-tab.h exactly
+# except that the VALUES structure is more appropriate for M4.  That is, VALUES
+# is a list of sublists of strings.  For each sublist, the first string is the
+# name of a %define variable, and all remaining strings in that sublist are the
+# valid values for that variable.  Complain if such a variable is undefined (a
+# Bison error since the default value should have been set already) or defined
+# to any other value (possibly a user error).  Don't record this as a Bison
+# usage of the variable as there's no reason to suspect that the value has yet
+# influenced the output.
+#
+# For example:
+#
+#   b4_percent_define_check_values([[[[foo]], [[foo-value1]], [[foo-value2]]]],
+#                                  [[[[bar]], [[bar-value1]]]])
+m4_define([b4_percent_define_check_values],
+[m4_foreach([b4_sublist], m4_quote($@),
+            [_b4_percent_define_check_values(b4_sublist)])])
+
+m4_define([_b4_percent_define_check_values],
+[m4_ifdef([b4_percent_define(]$1[)],
+  [m4_pushdef([b4_good_value], [0])dnl
+   m4_if($#, 1, [],
+         [m4_foreach([b4_value], m4_dquote(m4_shift($@)),
+                     [m4_if(m4_indir([b4_percent_define(]$1[)]), b4_value,
+                            [m4_define([b4_good_value], [1])])])])dnl
+   m4_if(b4_good_value, [0],
+         [b4_complain_at(b4_percent_define_get_loc([$1]),
+                         [[invalid value for %%define variable '%s': '%s']],
+                         [$1],
+                         m4_dquote(m4_indir([b4_percent_define(]$1[)])))
+          m4_foreach([b4_value], m4_dquote(m4_shift($@)),
+                     [b4_complain_at(b4_percent_define_get_loc([$1]),
+                                     [[accepted value: '%s']],
+                                     m4_dquote(b4_value))])])dnl
+   m4_popdef([b4_good_value])],
+  [b4_fatal([[b4_percent_define_check_values: undefined %%define variable '%s']], [$1])])])
 
 # b4_percent_code_get([QUALIFIER])
 # --------------------------------
 # If any %code blocks for QUALIFIER are defined, emit them beginning with a
 # comment and ending with synclines and a newline.  If QUALIFIER is not
 # specified or empty, do this for the unqualified %code blocks.  Also, record
-# the skeleton's usage of QUALIFIER (if specified) by defining
-# b4_percent_code_skeleton_qualifiers(QUALIFIER).
+# Bison's usage of QUALIFIER (if specified) by defining
+# b4_percent_code_bison_qualifiers(QUALIFIER).
 #
 # For example, to emit any unqualified %code blocks followed by any %code
 # blocks for the qualifier foo:
@@ -399,10 +545,10 @@ m4_define([b4_percent_define_default],
 #   b4_percent_code_get([[foo]])
 m4_define([b4_percent_code_get],
 [m4_pushdef([b4_macro_name], [[b4_percent_code(]$1[)]])dnl
-m4_ifval([$1], [m4_define([b4_percent_code_skeleton_qualifiers(]$1[)])])dnl
+m4_ifval([$1], [m4_define([b4_percent_code_bison_qualifiers(]$1[)])])dnl
 m4_ifdef(b4_macro_name,
 [b4_comment([m4_if([$#], [0], [[Unqualified %code]],
-                   [[%code "]$1["]])[ blocks.]])
+                   [["%code ]$1["]])[ blocks.]])
 b4_user_code([m4_indir(b4_macro_name)])
 ])dnl
 m4_popdef([b4_macro_name])])
@@ -411,26 +557,26 @@ m4_popdef([b4_macro_name])])
 # -----------------------------------------------------
 # If any %code blocks for QUALIFIER (or unqualified %code blocks if
 # QUALIFIER is empty) are defined, expand IF-TRUE, else expand IF-FALSE.
-# Also, record the skeleton's usage of QUALIFIER (if specified) by defining
-# b4_percent_code_skeleton_qualifiers(QUALIFIER).
+# Also, record Bison's usage of QUALIFIER (if specified) by defining
+# b4_percent_code_bison_qualifiers(QUALIFIER).
 m4_define([b4_percent_code_ifdef],
 [m4_ifdef([b4_percent_code(]$1[)],
-          [m4_ifval([$1], [m4_define([b4_percent_code_skeleton_qualifiers(]$1[)])])$2],
+          [m4_ifval([$1], [m4_define([b4_percent_code_bison_qualifiers(]$1[)])])$2],
 	  [$3])])
 
 
-## --------------------------------------------------------- ##
-## After processing the skeletons, check that all the user's ##
-## %define variables and %code qualifiers were used.         ##
-## --------------------------------------------------------- ##
+## ----------------------------------------------------------- ##
+## After processing the skeletons, check that all the user's   ##
+## %define variables and %code qualifiers were used by Bison.  ##
+## ----------------------------------------------------------- ##
 
 m4_define([b4_check_user_names_wrap],
 [m4_ifdef([b4_percent_]$1[_user_]$2[s],
           [b4_check_user_names([[%]$1 $2],
                                [b4_percent_]$1[_user_]$2[s],
-                               [[b4_percent_]$1[_skeleton_]$2[s]])])])
+                               [[b4_percent_]$1[_bison_]$2[s]])])])
 
-m4_wrap([
+m4_wrap_lifo([
 b4_check_user_names_wrap([[define]], [[variable]])
 b4_check_user_names_wrap([[code]], [[qualifier]])
 ])