+
+## ---------------- ##
+## api.value.type. ##
+## ---------------- ##
+
+
+# ---------------------- #
+# api.value.type=union. #
+# ---------------------- #
+
+# b4_symbol_type_register(SYMBOL-NUM)
+# -----------------------------------
+# Symbol SYMBOL-NUM has a type (for variant) instead of a type-tag.
+# Extend the definition of %union's body with a field of that type,
+# and extend the symbol's "type" field to point to the field name,
+# instead of the type name.
+m4_define([b4_symbol_type_register],
+[m4_define([b4_symbol($1, type_tag)],
+ [b4_symbol_if([$1], [has_id],
+ [b4_symbol([$1], [id])],
+ [yytype_[]b4_symbol([$1], [number])])])dnl
+m4_append([b4_user_union_members],
+m4_expand([
+ b4_symbol_tag_comment([$1])dnl
+ b4_symbol([$1], [type]) b4_symbol([$1], [type_tag]);]))
+])
+
+
+# b4_type_define_tag(SYMBOL1-NUM, ...)
+# ------------------------------------
+# For the batch of symbols SYMBOL1-NUM... (which all have the same
+# type), enhance the %union definition for each of them, and set
+# there "type" field to the field tag name, instead of the type name.
+m4_define([b4_type_define_tag],
+[b4_symbol_if([$1], [has_type],
+ [m4_map([b4_symbol_type_register], [$@])])
+])
+
+
+# b4_symbol_value_union(VAL, [TYPE])
+# ----------------------------------
+# Same of b4_symbol_value, but when api.value.type=union.
+m4_define([b4_symbol_value_union],
+[m4_ifval([$2],
+ [(*($2*)(&$1))],
+ [$1])])
+])
+
+
+# b4_value_type_setup_union
+# -------------------------
+# Setup support for api.value.type=union. Symbols are defined with a
+# type instead of a union member name: build the corresponding union,
+# and give the symbols their tag.
+m4_define([b4_value_type_setup_union],
+[m4_define([b4_union_members])
+b4_type_foreach([b4_type_define_tag])
+m4_copy_force([b4_symbol_value_union], [b4_symbol_value])
+])
+
+
+# ---------------- #
+# api.value.type. #
+# ---------------- #
+
+
+# b4_value_type_setup_variant
+# ---------------------------
+# Setup support for api.value.type=variant. By default, fail, specialized
+# by other skeletons.
+m4_define([b4_value_type_setup_variant],
+[b4_complain_at(b4_percent_define_get_loc([[api.value.type]]),
+ [['%s' does not support '%s']],
+ [b4_skeleton],
+ [%define api.value.type variant])])
+
+
+# _b4_value_type_setup_keyword
+# ----------------------------
+# api.value.type is defined with a keyword/string syntax. Check if
+# that is properly defined, and prepare its use.
+m4_define([_b4_value_type_setup_keyword],
+[b4_percent_define_check_values([[[[api.value.type]],
+ [[none]],
+ [[union]],
+ [[union-directive]],
+ [[variant]],
+ [[yystype]]]])dnl
+m4_case(b4_percent_define_get([[api.value.type]]),
+ [union], [b4_value_type_setup_union],
+ [variant], [b4_value_type_setup_variant])])
+
+
+# b4_value_type_setup
+# -------------------
+# Check if api.value.type is properly defined, and possibly prepare
+# its use.
+b4_define_silent([b4_value_type_setup],
+[# Define default value.
+b4_percent_define_ifdef([[api.value.type]], [],
+[# %union => api.value.type=union-directive
+m4_ifdef([b4_union_members],
+[m4_define([b4_percent_define_kind(api.value.type)], [keyword])
+m4_define([b4_percent_define(api.value.type)], [union-directive])],
+[# no tag seen => api.value.type={int}
+m4_if(b4_tag_seen_flag, 0,
+[m4_define([b4_percent_define_kind(api.value.type)], [code])
+m4_define([b4_percent_define(api.value.type)], [int])],
+[# otherwise api.value.type=yystype
+m4_define([b4_percent_define_kind(api.value.type)], [keyword])
+m4_define([b4_percent_define(api.value.type)], [yystype])])])])
+
+# Set up.
+m4_bmatch(b4_percent_define_get_kind([[api.value.type]]),
+ [keyword\|string], [_b4_value_type_setup_keyword])
+])
+
+
+## -------------- ##
+## Declarations. ##
+## -------------- ##
+
+
+# b4_value_type_define
+# --------------------
+m4_define([b4_value_type_define],
+[b4_value_type_setup[]dnl
+/* Value type. */
+m4_bmatch(b4_percent_define_get_kind([[api.value.type]]),
+[code],
+[[#if ! defined ]b4_api_PREFIX[STYPE && ! defined ]b4_api_PREFIX[STYPE_IS_DECLARED
+typedef ]b4_percent_define_get([[api.value.type]])[ ]b4_api_PREFIX[STYPE;
+# define ]b4_api_PREFIX[STYPE_IS_TRIVIAL 1
+# define ]b4_api_PREFIX[STYPE_IS_DECLARED 1
+#endif
+]],
+[m4_bmatch(b4_percent_define_get([[api.value.type]]),
+[union\|union-directive],
+[[#if ! defined ]b4_api_PREFIX[STYPE && ! defined ]b4_api_PREFIX[STYPE_IS_DECLARED
+typedef union ]b4_union_name[ ]b4_api_PREFIX[STYPE;
+union ]b4_union_name[
+{
+]b4_user_union_members[
+};
+# define ]b4_api_PREFIX[STYPE_IS_TRIVIAL 1
+# define ]b4_api_PREFIX[STYPE_IS_DECLARED 1
+#endif
+]])])])
+
+
+# b4_location_type_define
+# -----------------------
+m4_define([b4_location_type_define],
+[[/* Location type. */
+#if ! defined ]b4_api_PREFIX[LTYPE && ! defined ]b4_api_PREFIX[LTYPE_IS_DECLARED
+typedef struct ]b4_api_PREFIX[LTYPE ]b4_api_PREFIX[LTYPE;
+struct ]b4_api_PREFIX[LTYPE
+{
+ int first_line;
+ int first_column;
+ int last_line;
+ int last_column;
+};
+# define ]b4_api_PREFIX[LTYPE_IS_DECLARED 1
+# define ]b4_api_PREFIX[LTYPE_IS_TRIVIAL 1
+#endif
+]])
+
+
+# b4_declare_yylstype
+# -------------------
+# Declarations that might either go into the header (if --defines) or
+# in the parser body. Declare YYSTYPE/YYLTYPE, and yylval/yylloc.
+m4_define([b4_declare_yylstype],
+[b4_value_type_define[]b4_locations_if([
+b4_location_type_define])
+
+b4_pure_if([], [[extern ]b4_api_PREFIX[STYPE ]b4_prefix[lval;
+]b4_locations_if([[extern ]b4_api_PREFIX[LTYPE ]b4_prefix[lloc;]])])[]dnl
+])
+
+
+# b4_YYDEBUG_define
+# -----------------
+m4_define([b4_YYDEBUG_define],
+[[/* Debug traces. */
+]m4_if(b4_api_prefix, [yy],
+[[#ifndef YYDEBUG
+# define YYDEBUG ]b4_parse_trace_if([1], [0])[
+#endif]],
+[[#ifndef ]b4_api_PREFIX[DEBUG
+# if defined YYDEBUG
+#if YYDEBUG
+# define ]b4_api_PREFIX[DEBUG 1
+# else
+# define ]b4_api_PREFIX[DEBUG 0
+# endif
+# else /* ! defined YYDEBUG */
+# define ]b4_api_PREFIX[DEBUG ]b4_parse_trace_if([1], [0])[
+# endif /* ! defined YYDEBUG */
+#endif /* ! defined ]b4_api_PREFIX[DEBUG */]])[]dnl
+])
+
+# b4_declare_yydebug
+# ------------------
+m4_define([b4_declare_yydebug],
+[b4_YYDEBUG_define[
+#if ]b4_api_PREFIX[DEBUG
+extern int ]b4_prefix[debug;
+#endif][]dnl
+])
+
+# b4_yylloc_default_define
+# ------------------------
+# Define YYLLOC_DEFAULT.
+m4_define([b4_yylloc_default_define],
+[[/* YYLLOC_DEFAULT -- Set CURRENT to span from RHS[1] to RHS[N].
+ If N is 0, then set CURRENT to the empty location which ends
+ the previous symbol: RHS[0] (always defined). */
+
+#ifndef YYLLOC_DEFAULT
+# define YYLLOC_DEFAULT(Current, Rhs, N) \
+ do \
+ if (N) \
+ { \
+ (Current).first_line = YYRHSLOC (Rhs, 1).first_line; \
+ (Current).first_column = YYRHSLOC (Rhs, 1).first_column; \
+ (Current).last_line = YYRHSLOC (Rhs, N).last_line; \
+ (Current).last_column = YYRHSLOC (Rhs, N).last_column; \
+ } \
+ else \
+ { \
+ (Current).first_line = (Current).last_line = \
+ YYRHSLOC (Rhs, 0).last_line; \
+ (Current).first_column = (Current).last_column = \
+ YYRHSLOC (Rhs, 0).last_column; \
+ } \
+ while (0)
+#endif
+]])
+
+# b4_yy_location_print_define
+# ---------------------------
+# Define YY_LOCATION_PRINT.
+m4_define([b4_yy_location_print_define],
+[b4_locations_if([[
+/* YY_LOCATION_PRINT -- Print the location on the stream.
+ This macro was not mandated originally: define only if we know
+ we won't break user code: when these are the locations we know. */
+
+#ifndef YY_LOCATION_PRINT
+# if defined ]b4_api_PREFIX[LTYPE_IS_TRIVIAL && ]b4_api_PREFIX[LTYPE_IS_TRIVIAL
+
+/* Print *YYLOCP on YYO. Private, do not rely on its existence. */
+
+__attribute__((__unused__))
+]b4_function_define([yy_location_print_],
+ [static unsigned],
+ [[FILE *yyo], [yyo]],
+ [[YYLTYPE const * const yylocp], [yylocp]])[
+{
+ unsigned res = 0;
+ int end_col = 0 != yylocp->last_column ? yylocp->last_column - 1 : 0;
+ if (0 <= yylocp->first_line)