[Top][All Lists]
[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
address@hidden
|
From: |
Paul Eggert |
|
Subject: |
address@hidden |
|
Date: |
Sun, 09 Jul 2006 13:45:11 -0700 |
|
User-agent: |
Gnus/5.1008 (Gnus v5.10.8) Emacs/21.4 (gnu/linux) |
I installed the following Bison patch to add the POSIX-required
support for typed Yacc grammars without %union.
2006-07-09 Paul Eggert <address@hidden>
* NEWS: Instead of %union, you can define and use your own union type
YYSTYPE if your grammar contains at least one <type> tag.
Your YYSTYPE need not be a macro; it can be a typedef.
* doc/bison.texinfo (Value Type, Multiple Types, Location Type):
(Union Decl, Decl Summary): Document this.
* data/glr.c (YYSTYPE): Implement this.
* data/glr.cc (YYSTYPE): Likewise.
* data/lalr1.cc (YYSTYPE): Likewise.
* data/yacc.c (YYSTYPE): Likewise.
* src/output.c (prepare): Output tag_seen_flag.
* src/parse-gram.y (declaration, grammar_declaration):
Use 'union_seen' rather than 'typed' to determine whether
%union has been seen, since grammars can now be typed without
%union.
(symbol_declaration, type.opt, symbol_def):
Keep track of whether a tag has been seen.
* src/reader.c (union_seen, tag_seen): New vars.
(typed): remove.
* src/reader.h (union_seen, tag_seen, typed): Likewise.
* src/scan-code.l (untyped_var_seen): New variable.
(handle_action_dollar): Adjust to above changes.
(handle_action_dollar, handle_action_at):
Improve overflow checking for outlandish numbers.
* tests/input.at (AT_CHECK_UNUSED_VALUES): Redo test to
avoid new diagnostics generated by above changes.
* tests/regression.at (YYSTYPE typedef): Add test to check
for type tags without %union.
Index: NEWS
===================================================================
RCS file: /cvsroot/bison/bison/NEWS,v
retrieving revision 1.154
diff -p -u -r1.154 NEWS
--- NEWS 8 Jul 2006 20:38:14 -0000 1.154
+++ NEWS 9 Jul 2006 20:28:36 -0000
@@ -3,6 +3,12 @@ Bison News
Changes in version 2.3+:
+* Instead of %union, you can define and use your own union type
+ YYSTYPE if your grammar contains at least one <type> tag.
+ Your YYSTYPE need not be a macro; it can be a typedef.
+ This change is for compatibility with other Yacc implementations,
+ and is required by POSIX.
+
* Locations columns and lines start at 1.
In accordance with the GNU Coding Standards and Emacs.
@@ -19,7 +25,7 @@ Changes in version 2.3+:
`%{ ... %}' syntax. To generate the pre-prologue, Bison concatenates all
prologue blocks that you've declared before the first %union. To generate
the post-prologue, Bison concatenates all prologue blocks that you've
- declared after the first %union.
+ declared after the first %union.
Previous releases of Bison inserted the pre-prologue into both the header
file and the code file in all cases except for LALR(1) parsers in C. In the
Index: doc/bison.texinfo
===================================================================
RCS file: /cvsroot/bison/bison/doc/bison.texinfo,v
retrieving revision 1.196
diff -p -u -r1.196 bison.texinfo
--- doc/bison.texinfo 8 Jul 2006 20:38:14 -0000 1.196
+++ doc/bison.texinfo 9 Jul 2006 20:28:37 -0000
@@ -3092,7 +3092,8 @@ the semantic values of all language cons
@acronym{RPN} and infix calculator examples (@pxref{RPN Calc, ,Reverse Polish
Notation Calculator}).
-Bison's default is to use type @code{int} for all semantic values. To
+Bison normally uses the type @code{int} for semantic values if your
+program uses the same data type for all language constructs. To
specify some other type, define @code{YYSTYPE} as a macro, like this:
@example
@@ -3119,9 +3120,11 @@ requires you to do two things:
@itemize @bullet
@item
-Specify the entire collection of possible data types, with the
+Specify the entire collection of possible data types, either by using the
@code{%union} Bison declaration (@pxref{Union Decl, ,The Collection of
-Value Types}).
+Value Types}), or by using a @code{typedef} or a @code{#define} to
+define @code{YYSTYPE} to be a union type whose member names are
+the type tags.
@item
Choose one of those types for each symbol (terminal or nonterminal) for
@@ -3500,7 +3503,7 @@ since all tokens and groupings always us
You can specify the type of locations by defining a macro called
@code{YYLTYPE}, just as you can specify the semantic value type by
-defining @code{YYSTYPE} (@pxref{Value Type}).
+defining a @code{YYSTYPE} macro (@pxref{Value Type}).
When @code{YYLTYPE} is not defined, Bison uses a default structure type with
four members:
@@ -3895,6 +3898,35 @@ only the first @code{%union} declaration
Note that, unlike making a @code{union} declaration in C, you need not write
a semicolon after the closing brace.
+Instead of @code{%union}, you can define and use your own union type
address@hidden if your grammar contains at least one
address@hidden<@var{type}>} tag. For example, you can put the following into
+a header file @file{parser.h}:
+
address@hidden
address@hidden
+union YYSTYPE @{
+ double val;
+ symrec *tptr;
address@hidden;
+typedef union YYSTYPE YYSTYPE;
address@hidden group
address@hidden example
+
address@hidden
+and then your grammar can use the following
+instead of @code{%union}:
+
address@hidden
address@hidden
address@hidden
+#include "parser.h"
address@hidden
+%type <val> expr
+%token <tptr> ID
address@hidden group
address@hidden example
+
@node Type Decl
@subsection Nonterminal Symbols
@cindex declaring value types, nonterminals
@@ -4212,10 +4244,13 @@ names defined in the grammar as well as
If the parser output file is named @address@hidden then this file
is named @address@hidden
-Unless @code{YYSTYPE} is already defined as a macro, the output header
-declares @code{YYSTYPE}. Therefore, if you are using a @code{%union}
+For C parsers, the output header declares @code{YYSTYPE} unless unless
address@hidden is already defined as a macro or you have used a
address@hidden<@var{type}>} tag without using @code{%union}.
+Therefore, if you are using a @code{%union}
(@pxref{Multiple Types, ,More Than One Value Type}) with components that
require other definitions, or if you have defined a @code{YYSTYPE} macro
+or type definition
(@pxref{Value Type, ,Data Types of Semantic Values}), you need to
arrange for these definitions to be propagated to all modules, e.g., by
putting them in a prerequisite header that is included both by your
@@ -4227,7 +4262,7 @@ Parser}.
If you have also used locations, the output header declares
@code{YYLTYPE} and @code{yylloc} using a protocol similar to that of
address@hidden and @code{yylval}. @xref{Locations, ,Tracking
+the @code{YYSTYPE} macro and @code{yylval}. @xref{Locations, ,Tracking
Locations}.
This output file is normally essential if you wish to put the definition
Index: data/glr.c
===================================================================
RCS file: /cvsroot/bison/bison/data/glr.c,v
retrieving revision 1.184
diff -p -u -r1.184 glr.c
--- data/glr.c 8 Jul 2006 20:38:14 -0000 1.184
+++ data/glr.c 9 Jul 2006 20:28:37 -0000
@@ -175,14 +175,15 @@ m4_define([b4_shared_declarations],
b4_token_enums(b4_tokens)
-[#if ! defined YYSTYPE && ! defined YYSTYPE_IS_DECLARED
+[#ifndef YYSTYPE
]m4_ifdef([b4_stype],
-[typedef union b4_union_name
-b4_user_stype
- YYSTYPE;],
-[typedef int YYSTYPE;])[
-# define YYSTYPE_IS_DECLARED 1
-# define YYSTYPE_IS_TRIVIAL 1
+[[typedef union ]b4_union_name[
+]b4_user_stype[
+ YYSTYPE;
+# define YYSTYPE_IS_TRIVIAL 1]],
+[m4_if(b4_tag_seen_flag, 0,
+[[typedef int YYSTYPE;
+# define YYSTYPE_IS_TRIVIAL 1]])])[
#endif
#if ! defined YYLTYPE && ! defined YYLTYPE_IS_DECLARED
Index: data/glr.cc
===================================================================
RCS file: /cvsroot/bison/bison/data/glr.cc,v
retrieving revision 1.23
diff -p -u -r1.23 glr.cc
--- data/glr.cc 8 Jul 2006 14:24:56 -0000 1.23
+++ data/glr.cc 9 Jul 2006 20:28:37 -0000
@@ -288,7 +288,9 @@ namespace ]b4_namespace[
[ union semantic_type
b4_user_stype
;],
-[ typedef int semantic_type;])[
+[m4_if(b4_tag_seen_flag, 0,
+[[ typedef int semantic_type;]],
+[[ typedef YYSTYPE semantic_type;]])])[
#else
typedef YYSTYPE semantic_type;
#endif
Index: data/lalr1.cc
===================================================================
RCS file: /cvsroot/bison/bison/data/lalr1.cc,v
retrieving revision 1.136
diff -p -u -r1.136 lalr1.cc
--- data/lalr1.cc 8 Jul 2006 14:24:56 -0000 1.136
+++ data/lalr1.cc 9 Jul 2006 20:28:37 -0000
@@ -110,7 +110,9 @@ namespace ]b4_namespace[
[ union semantic_type
b4_user_stype
;],
-[ typedef int semantic_type;])[
+[m4_if(b4_tag_seen_flag, 0,
+[[ typedef int semantic_type;]],
+[[ typedef YYSTYPE semantic_type;]])])[
#else
typedef YYSTYPE semantic_type;
#endif
Index: data/yacc.c
===================================================================
RCS file: /cvsroot/bison/bison/data/yacc.c,v
retrieving revision 1.149
diff -p -u -r1.149 yacc.c
--- data/yacc.c 9 Jul 2006 07:38:12 -0000 1.149
+++ data/yacc.c 9 Jul 2006 20:28:37 -0000
@@ -189,13 +189,15 @@ b4_token_enums_defines(b4_tokens)[
#if ! defined YYSTYPE && ! defined YYSTYPE_IS_DECLARED
]m4_ifdef([b4_stype],
-[[typedef union ]b4_union_name
-b4_user_stype
- YYSTYPE;],
-[typedef int YYSTYPE;])[
+[[typedef union ]b4_union_name[
+]b4_user_stype[
+ YYSTYPE;
+# define YYSTYPE_IS_TRIVIAL 1]],
+[m4_if(b4_tag_seen_flag, 0,
+[[typedef int YYSTYPE;
+# define YYSTYPE_IS_TRIVIAL 1]])])[
# define yystype YYSTYPE /* obsolescent; will be withdrawn */
# define YYSTYPE_IS_DECLARED 1
-# define YYSTYPE_IS_TRIVIAL 1
#endif
]b4_locations_if([#if ! defined YYLTYPE && ! defined YYLTYPE_IS_DECLARED
@@ -1499,13 +1501,15 @@ b4_token_enums_defines(b4_tokens)
[#if ! defined YYSTYPE && ! defined YYSTYPE_IS_DECLARED
]m4_ifdef([b4_stype],
-[[typedef union ]b4_union_name
-b4_user_stype
- YYSTYPE;],
-[typedef int YYSTYPE;])[
+[[typedef union ]b4_union_name[
+]b4_user_stype[
+ YYSTYPE;
+# define YYSTYPE_IS_TRIVIAL 1]],
+[m4_if(b4_tag_seen_flag, 0,
+[[typedef int YYSTYPE;
+# define YYSTYPE_IS_TRIVIAL 1]])])[
# define yystype YYSTYPE /* obsolescent; will be withdrawn */
# define YYSTYPE_IS_DECLARED 1
-# define YYSTYPE_IS_TRIVIAL 1
#endif
]b4_pure_if([],
Index: src/output.c
===================================================================
RCS file: /cvsroot/bison/bison/src/output.c,v
retrieving revision 1.250
diff -p -u -r1.250 output.c
--- src/output.c 11 Jun 2006 18:27:44 -0000 1.250
+++ src/output.c 9 Jul 2006 20:28:37 -0000
@@ -590,6 +590,7 @@ prepare (void)
MUSCLE_INSERT_BOOL ("locations_flag", locations_flag);
MUSCLE_INSERT_BOOL ("pure_flag", pure_parser);
MUSCLE_INSERT_BOOL ("synclines_flag", !no_lines_flag);
+ MUSCLE_INSERT_BOOL ("tag_seen_flag", tag_seen);
MUSCLE_INSERT_BOOL ("yacc_flag", yacc_flag);
/* File names. */
Index: src/parse-gram.y
===================================================================
RCS file: /cvsroot/bison/bison/src/parse-gram.y,v
retrieving revision 1.84
diff -p -u -r1.84 parse-gram.y
--- src/parse-gram.y 9 Jul 2006 03:44:51 -0000 1.84
+++ src/parse-gram.y 9 Jul 2006 20:28:37 -0000
@@ -57,7 +57,7 @@ static char const *char_name (char);
static void add_param (char const *, char *, location);
static symbol_class current_class = unknown_sym;
-static uniqstr current_type = 0;
+static uniqstr current_type = NULL;
static symbol *current_lhs;
static location current_lhs_location;
static int current_prec = 0;
@@ -209,7 +209,7 @@ declaration:
grammar_declaration
| PROLOGUE
{
- prologue_augment (translate_code ($1, @1), @1, typed);
+ prologue_augment (translate_code ($1, @1), @1, union_seen);
}
| "%after-header" "{...}"
{
@@ -322,7 +322,7 @@ grammar_declaration:
{
char const *body = $3;
- if (typed)
+ if (union_seen)
{
/* Concatenate the union bodies, turning the first one's
trailing '}' into '\n', and omitting the second one's '{'. */
@@ -331,7 +331,7 @@ grammar_declaration:
body++;
}
- typed = true;
+ union_seen = true;
muscle_code_grow ("stype", body, @3);
}
;
@@ -352,6 +352,7 @@ symbol_declaration:
}
| "%type" TYPE symbols.1
{
+ tag_seen = true;
symbol_list *list;
for (list = $3; list; list = list->next)
symbol_type_set (list->sym, $2, @2);
@@ -382,7 +383,7 @@ precedence_declarator:
type.opt:
/* Nothing. */ { current_type = NULL; }
-| TYPE { current_type = $1; }
+| TYPE { current_type = $1; tag_seen = true; }
;
/* One or more nonterminals to be %typed. */
@@ -396,6 +397,7 @@ symbol_def:
TYPE
{
current_type = $1;
+ tag_seen = true;
}
| id
{
Index: src/reader.c
===================================================================
RCS file: /cvsroot/bison/bison/src/reader.c,v
retrieving revision 1.264
diff -p -u -r1.264 reader.c
--- src/reader.c 9 Jul 2006 16:38:31 -0000 1.264
+++ src/reader.c 9 Jul 2006 20:28:37 -0000
@@ -45,7 +45,10 @@ static bool start_flag = false;
merger_list *merge_functions;
/* Was %union seen? */
-bool typed = false;
+bool union_seen = false;
+
+/* Was a tag seen? */
+bool tag_seen = false;
/* Should rules have a default precedence? */
bool default_prec = true;
Index: src/reader.h
===================================================================
RCS file: /cvsroot/bison/bison/src/reader.h,v
retrieving revision 1.54
diff -p -u -r1.54 reader.h
--- src/reader.h 26 Jun 2006 04:45:24 -0000 1.54
+++ src/reader.h 9 Jul 2006 20:28:37 -0000
@@ -59,7 +59,10 @@ void free_merger_functions (void);
extern merger_list *merge_functions;
/* Was %union seen? */
-extern bool typed;
+extern bool union_seen;
+
+/* Was a tag seen? */
+extern bool tag_seen;
/* Should rules have a default precedence? */
extern bool default_prec;
Index: src/scan-code.l
===================================================================
RCS file: /cvsroot/bison/bison/src/scan-code.l,v
retrieving revision 1.8
diff -p -u -r1.8 scan-code.l
--- src/scan-code.l 26 Jun 2006 04:29:34 -0000 1.8
+++ src/scan-code.l 9 Jul 2006 20:28:37 -0000
@@ -55,6 +55,9 @@ static void handle_action_dollar (symbol
static void handle_action_at (symbol_list *rule, char *cp, location at_loc);
static location the_location;
static location *loc = &the_location;
+
+/* True if an untyped $$ or $n was seen. */
+static bool untyped_var_seen;
%}
/* C and C++ comments in code. */
%x SC_COMMENT SC_LINE_COMMENT
@@ -262,48 +265,62 @@ handle_action_dollar (symbol_list *rule,
++cp;
*cp = '\0';
++cp;
+ if (untyped_var_seen)
+ complain_at (dollar_loc, _("explicit type given in untyped grammar"));
+ tag_seen = true;
}
if (*cp == '$')
{
if (!type_name)
type_name = symbol_list_n_type_name_get (rule, dollar_loc, 0);
- if (!type_name && typed)
+
+ if (!type_name)
{
- if (rule->midrule_parent_rule)
- complain_at (dollar_loc,
- _("$$ for the midrule at $%d of `%s' has no declared"
- " type"),
- rule->midrule_parent_rhs_index,
- effective_rule->sym->tag);
+ if (union_seen | tag_seen)
+ {
+ if (rule->midrule_parent_rule)
+ complain_at (dollar_loc,
+ _("$$ for the midrule at $%d of `%s'"
+ " has no declared type"),
+ rule->midrule_parent_rhs_index,
+ effective_rule->sym->tag);
+ else
+ complain_at (dollar_loc, _("$$ of `%s' has no declared type"),
+ rule->sym->tag);
+ }
else
- complain_at (dollar_loc, _("$$ of `%s' has no declared type"),
- rule->sym->tag);
+ untyped_var_seen = true;
+ type_name = "";
}
- if (!type_name)
- type_name = "";
+
obstack_fgrow1 (&obstack_for_string,
"]b4_lhs_value([%s])[", type_name);
rule->used = true;
}
else
{
- long int num;
- set_errno (0);
- num = strtol (cp, 0, 10);
- if (INT_MIN <= num && num <= effective_rule_length && ! get_errno ())
+ long int num = strtol (cp, NULL, 10);
+
+ if (1 - INT_MAX + effective_rule_length <= num
+ && num <= effective_rule_length)
{
int n = num;
- if (1-n > max_left_semantic_context)
- max_left_semantic_context = 1-n;
- if (!type_name && n > 0)
+ if (max_left_semantic_context < 1 - n)
+ max_left_semantic_context = 1 - n;
+ if (!type_name && 0 < n)
type_name =
symbol_list_n_type_name_get (effective_rule, dollar_loc, n);
- if (!type_name && typed)
- complain_at (dollar_loc, _("$%d of `%s' has no declared type"),
- n, effective_rule->sym->tag);
if (!type_name)
- type_name = "";
+ {
+ if (union_seen | tag_seen)
+ complain_at (dollar_loc, _("$%d of `%s' has no declared type"),
+ n, effective_rule->sym->tag);
+ else
+ untyped_var_seen = true;
+ type_name = "";
+ }
+
obstack_fgrow3 (&obstack_for_string,
"]b4_rhs_value(%d, %d, [%s])[",
effective_rule_length, n, type_name);
@@ -336,11 +353,10 @@ handle_action_at (symbol_list *rule, cha
obstack_sgrow (&obstack_for_string, "]b4_lhs_location[");
else
{
- long int num;
- set_errno (0);
- num = strtol (cp, 0, 10);
+ long int num = strtol (cp, NULL, 10);
- if (INT_MIN <= num && num <= effective_rule_length && ! get_errno ())
+ if (1 - INT_MAX + effective_rule_length <= num
+ && num <= effective_rule_length)
{
int n = num;
obstack_fgrow2 (&obstack_for_string, "]b4_rhs_location(%d, %d)[",
@@ -356,9 +372,9 @@ handle_action_at (symbol_list *rule, cha
| Initialize the scanner. |
`-------------------------*/
-/* Translate the dollars and ats in \a a, whose location is l.
- Depending on the \a sc_context (SC_RULE_ACTION, SC_SYMBOL_ACTION,
- INITIAL), the processing is different. */
+/* Translate the dollars and ats in \a a, whose location is \a l. The
+ translation is for \a rule, in the context \a sc_context
+ (SC_RULE_ACTION, SC_SYMBOL_ACTION, INITIAL). */
static const char *
translate_action (int sc_context, symbol_list *rule, const char *a, location l)
Index: tests/input.at
===================================================================
RCS file: /cvsroot/bison/bison/tests/input.at,v
retrieving revision 1.49
diff -p -u -r1.49 input.at
--- tests/input.at 8 Jul 2006 00:02:04 -0000 1.49
+++ tests/input.at 9 Jul 2006 20:28:37 -0000
@@ -107,12 +107,12 @@ c: INT | INT { $]1[ } INT { } INT { };
d: INT | INT { } INT { $]1[ } INT { };
e: INT | INT { } INT { } INT { $]1[ };
f: INT | INT { } INT { } INT { $]$[ = $]1[ + $]3[ + $]5[; };
-g: INT | INT { $]$[ } INT { $]$[ } INT { };
-h: INT | INT { $]$[ } INT { $]$[ = $]2[ } INT { };
+g: INT | INT { $<integer>$; } INT { $<integer>$; } INT { };
+h: INT | INT { $<integer>$; } INT { $<integer>$ = $<integer>2; } INT { };
i: INT | INT INT { } { $]$[ = $]1[ + $]2[; };
j: INT | INT INT { $<integer>$ = 1; } { $]$[ = $]1[ + $]2[; };
-k: INT | INT INT { $]$[; } { $]$[ = $]3[; } { };
-l: INT | INT { $]$[ = $]1[; } INT { $]$[ = $]2[ + $]3[; } INT { $]$[ = $]4[ +
$]5[; };]]m4_ifval($1, [
+k: INT | INT INT { $<integer>$; } { $<integer>$ = $<integer>3; } { };
+l: INT | INT { $<integer>$ = $<integer>1; } INT { $<integer>$ = $<integer>2 +
$<integer>3; } INT { $<integer>$ = $<integer>4 + $<integer>5; };]]m4_ifval($1, [
_AT_UNUSED_VALUES_DECLARATIONS])
)
@@ -131,22 +131,22 @@ input.y:14.10-35: warning: unused value:
input.y:15.10-36: warning: unset value: $]$[
input.y:15.10-36: warning: unused value: $]3[
input.y:15.10-36: warning: unused value: $]5[
-input.y:17.10-38: warning: unset value: $]$[
-input.y:17.10-38: warning: unused value: $]1[
-input.y:17.10-38: warning: unused value: $]2[
-input.y:17.10-38: warning: unused value: $]3[
-input.y:17.10-38: warning: unused value: $]4[
-input.y:17.10-38: warning: unused value: $]5[
-input.y:18.10-43: warning: unset value: $]$[
-input.y:18.10-43: warning: unused value: $]1[
-input.y:18.10-43: warning: unused value: $]3[
-input.y:18.10-43: warning: unused value: $]4[
-input.y:18.10-43: warning: unused value: $]5[
+input.y:17.10-58: warning: unset value: $]$[
+input.y:17.10-58: warning: unused value: $]1[
+input.y:17.10-58: warning: unused value: $]2[
+input.y:17.10-58: warning: unused value: $]3[
+input.y:17.10-58: warning: unused value: $]4[
+input.y:17.10-58: warning: unused value: $]5[
+input.y:18.10-72: warning: unset value: $]$[
+input.y:18.10-72: warning: unused value: $]1[
+input.y:18.10-72: warning: unused value: $]3[
+input.y:18.10-72: warning: unused value: $]4[
+input.y:18.10-72: warning: unused value: $]5[
input.y:20.10-55: warning: unused value: $]3[
-input.y:21.10-41: warning: unset value: $]$[
-input.y:21.10-41: warning: unused value: $]1[
-input.y:21.10-41: warning: unused value: $]2[
-input.y:21.10-41: warning: unused value: $]4[
+input.y:21.10-68: warning: unset value: $]$[
+input.y:21.10-68: warning: unused value: $]1[
+input.y:21.10-68: warning: unused value: $]2[
+input.y:21.10-68: warning: unused value: $]4[
]])])
Index: tests/regression.at
===================================================================
RCS file: /cvsroot/bison/bison/tests/regression.at,v
retrieving revision 1.103
diff -p -u -r1.103 regression.at
--- tests/regression.at 25 Jun 2006 06:59:54 -0000 1.103
+++ tests/regression.at 9 Jul 2006 20:28:37 -0000
@@ -49,6 +49,33 @@ AT_CLEANUP
+## ----------------- ##
+## YYSTYPE typedef. ##
+## ----------------- ##
+
+AT_SETUP([YYSTYPE typedef])
+
+AT_DATA_GRAMMAR([input.y],
+[[%{
+void yyerror (char const *);
+int yylex (void);
+typedef union { char const *val; } YYSTYPE;
+%}
+
+%type <val> program
+
+%%
+
+program: { $$ = ""; };
+]])
+
+AT_CHECK([bison -o input.c input.y])
+AT_COMPILE([input.o], [-c input.c])
+
+AT_CLEANUP
+
+
+
## ------------------------------------- ##
## Early token definitions with --yacc. ##
## ------------------------------------- ##
- address@hidden,
Paul Eggert <=