+# b4_check_user_names(WHAT, USER-LIST, BISON-NAMESPACE)
+# --------------------------------------------------------
+# Warn 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
+# occurrence: name, start boundary, and end boundary. Empty string names are
+# fine. An empty list is fine.
+#
+# For example, to define b4_foo_user_names to be used for USER-LIST with three
+# name occurrences and with correct quoting:
+#
+# m4_define([b4_foo_user_names],
+# [[[[[[bar]], [[parser.y:1.7]], [[parser.y:1.16]]]],
+# [[[[bar]], [[parser.y:5.7]], [[parser.y:5.16]]]],
+# [[[[baz]], [[parser.y:8.7]], [[parser.y:8.16]]]]]])
+#
+# 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_bison_names for BISON-NAMESPACE and define that
+# the names bar and baz are used by Bison:
+#
+# 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 BISON-NAMESPACE b4_foo_bison_names, and with correct
+# quoting:
+#
+# b4_check_user_names([[foo]], [b4_foo_user_names],
+# [[b4_foo_bison_names]])
+m4_define([b4_check_user_names],
+[m4_foreach([b4_occurrence], $2,
+[m4_pushdef([b4_occurrence], b4_occurrence)dnl
+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
+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)
+# -------------------------------
+# If the %define variable VARIABLE is defined, emit its value. 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_bison_variables(]$1[)])dnl
+m4_ifdef([b4_percent_define(]$1[)], [m4_indir([b4_percent_define(]$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 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_bison_variables(]$1[)])$2],
+ [$3])])
+
+# b4_percent_define_flag_if(VARIABLE, IF-TRUE, [IF-FALSE])
+# --------------------------------------------------------
+# 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]),
+ [], [$2], [true], [$2], [false], [$3],
+ [m4_expand_once([dnl
+ m4_pushdef([b4_loc], m4_indir([b4_percent_define_loc(]$1[)]))dnl
+ b4_complain_at(b4_loc,
+ [[invalid value for %%define boolean variable `%s']],
+ [$1])dnl
+ m4_popdef([b4_loc])],
+ [[b4_percent_define_flag_if($1)]])])],
+ [b4_fatal([[undefined %%define variable `%s' passed to b4_percent_define_flag_if]], [$1])])])
+
+# b4_percent_define_default(VARIABLE, 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])dnl
+ m4_define([b4_percent_define_loc(]$1[)],
+ [[[[[Bison:b4_percent_define_default]:0.0]], [[[Bison:b4_percent_define_default]:0.0]]]])])])
+
+# 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
+# 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:
+#
+# b4_percent_code_get
+# 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_bison_qualifiers(]$1[)])])dnl
+m4_ifdef(b4_macro_name,
+[b4_comment([m4_if([$#], [0], [[Unqualified %code]],
+ [[%code "]$1["]])[ blocks.]])
+b4_user_code([m4_indir(b4_macro_name)])
+])dnl
+m4_popdef([b4_macro_name])])
+
+# b4_percent_code_ifdef(QUALIFIER, IF-TRUE, [IF-FALSE])
+# -----------------------------------------------------
+# 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 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_bison_qualifiers(]$1[)])])$2],
+ [$3])])
+
+
+## ----------------------------------------------------------- ##
+## 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[_bison_]$2[s]])])])
+
+m4_wrap([
+b4_check_user_names_wrap([[define]], [[variable]])
+b4_check_user_names_wrap([[code]], [[qualifier]])
+])