src/parse-gram.y

/* Bison Grammar Parser                             -*- C -*-

   Copyright (C) 2002-2015, 2018-2019 Free Software Foundation, Inc.

   This file is part of Bison, the GNU Compiler Compiler.

   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 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, see <http://www.gnu.org/licenses/>.  */

%code requires
{
  #include "symlist.h"
  #include "symtab.h"
}

%code top
{
  /* On column 0 to please syntax-check.  */
#include <config.h>
}

%code
{
  #include "system.h"

  #include <c-ctype.h>
  #include <errno.h>
  #include <intprops.h>
  #include <quotearg.h>
  #include <vasnprintf.h>
  #include <xmemdup0.h>

  #include "complain.h"
  #include "conflicts.h"
  #include "files.h"
  #include "getargs.h"
  #include "gram.h"
  #include "named-ref.h"
  #include "reader.h"
  #include "scan-code.h"
  #include "scan-gram.h"

  static int current_prec = 0;
  static location current_lhs_loc;
  static named_ref *current_lhs_named_ref;
  static symbol *current_lhs_symbol;
  static symbol_class current_class = unknown_sym;

  /** Set the new current left-hand side symbol, possibly common
   * to several right-hand side parts of rule.
   */
  static void current_lhs (symbol *sym, location loc, named_ref *ref);

  #define YYLLOC_DEFAULT(Current, Rhs, N)         \
    (Current) = lloc_default (Rhs, N)
  static YYLTYPE lloc_default (YYLTYPE const *, int);

  #define YY_LOCATION_PRINT(File, Loc)            \
    location_print (Loc, File)

  /* Strip initial '{' and final '}' (must be first and last characters).
     Return the result.  */
  static char *strip_braces (char *code);

  /* Convert CODE by calling code_props_plain_init if PLAIN, otherwise
     code_props_symbol_action_init.  Call
     gram_scanner_last_string_free to release the latest string from
     the scanner (should be CODE). */
  static char const *translate_code (char *code, location loc, bool plain);

  /* Convert CODE by calling code_props_plain_init after having
     stripped the first and last characters (expected to be '{', and
     '}').  Call gram_scanner_last_string_free to release the latest
     string from the scanner (should be CODE). */
  static char const *translate_code_braceless (char *code, location loc);

  /* Handle a %error-verbose directive.  */
  static void handle_error_verbose (location const *loc, char const *directive);

  /* Handle a %file-prefix directive.  */
  static void handle_file_prefix (location const *loc,
                                  location const *dir_loc,
                                  char const *directive, char const *value);

  /* Handle a %name-prefix directive.  */
  static void handle_name_prefix (location const *loc,
                                  char const *directive, char const *value);

  /* Handle a %pure-parser directive.  */
  static void handle_pure_parser (location const *loc, char const *directive);

  /* Handle a %require directive.  */
  static void handle_require (location const *loc, char const *version);

  /* Handle a %skeleton directive.  */
  static void handle_skeleton (location const *loc, char const *skel);

  /* Handle a %yacc directive.  */
  static void handle_yacc (location const *loc);

  /* Implementation of yyerror.  */
  static void gram_error (location const *, char const *);

  /* A string that describes a char (e.g., 'a' -> "'a'").  */
  static char const *char_name (char);

  /* Add style to semantic values in traces.  */
  static void tron (FILE *yyo);
  static void troff (FILE *yyo);
}

%define api.header.include {"parse-gram.h"}
%define api.prefix {gram_}
%define api.pure full
%define api.token.raw
%define api.value.type union
%define locations
%define parse.error verbose
%define parse.lac full
%define parse.trace
%defines
%expect 0
%verbose

%initial-action
{
  /* Bison's grammar can initial empty locations, hence a default
     location is needed. */
  boundary_set (&@$.start, grammar_file, 1, 1, 1);
  boundary_set (&@$.end, grammar_file, 1, 1, 1);
}

/* Define the tokens together with their human representation.  */
%token GRAM_EOF 0 "end of file"
%token STRING     "string"

%token PERCENT_TOKEN       "%token"
%token PERCENT_NTERM       "%nterm"

%token PERCENT_TYPE        "%type"
%token PERCENT_DESTRUCTOR  "%destructor"
%token PERCENT_PRINTER     "%printer"

%token PERCENT_LEFT        "%left"
%token PERCENT_RIGHT       "%right"
%token PERCENT_NONASSOC    "%nonassoc"
%token PERCENT_PRECEDENCE  "%precedence"

%token PERCENT_PREC          "%prec"
%token PERCENT_DPREC         "%dprec"
%token PERCENT_MERGE         "%merge"

/*----------------------.
| Global Declarations.  |
`----------------------*/

%token
  PERCENT_CODE            "%code"
  PERCENT_DEFAULT_PREC    "%default-prec"
  PERCENT_DEFINE          "%define"
  PERCENT_DEFINES         "%defines"
  PERCENT_ERROR_VERBOSE   "%error-verbose"
  PERCENT_EXPECT          "%expect"
  PERCENT_EXPECT_RR       "%expect-rr"
  PERCENT_FLAG            "%<flag>"
  PERCENT_FILE_PREFIX     "%file-prefix"
  PERCENT_GLR_PARSER      "%glr-parser"
  PERCENT_INITIAL_ACTION  "%initial-action"
  PERCENT_LANGUAGE        "%language"
  PERCENT_NAME_PREFIX     "%name-prefix"
  PERCENT_NO_DEFAULT_PREC "%no-default-prec"
  PERCENT_NO_LINES        "%no-lines"
  PERCENT_NONDETERMINISTIC_PARSER
                          "%nondeterministic-parser"
  PERCENT_OUTPUT          "%output"
  PERCENT_PURE_PARSER     "%pure-parser"
  PERCENT_REQUIRE         "%require"
  PERCENT_SKELETON        "%skeleton"
  PERCENT_START           "%start"
  PERCENT_TOKEN_TABLE     "%token-table"
  PERCENT_VERBOSE         "%verbose"
  PERCENT_YACC            "%yacc"
;

%token BRACED_CODE     "{...}"
%token BRACED_PREDICATE "%?{...}"
%token BRACKETED_ID    "[identifier]"
%token CHAR            "character literal"
%token COLON           ":"
%token EPILOGUE        "epilogue"
%token EQUAL           "="
%token ID              "identifier"
%token ID_COLON        "identifier:"
%token PERCENT_PERCENT "%%"
%token PIPE            "|"
%token PROLOGUE        "%{...%}"
%token SEMICOLON       ";"
%token TAG             "<tag>"
%token TAG_ANY         "<*>"
%token TAG_NONE        "<>"

 /* Experimental feature, don't rely on it.  */
%code pre-printer  {tron (yyo);}
%code post-printer {troff (yyo);}

%type <unsigned char> CHAR
%printer { fputs (char_name ($$), yyo); } <unsigned char>

%type <char*> "{...}" "%?{...}" "%{...%}" EPILOGUE STRING
%printer { fputs ($$, yyo); }  <char*>

%type <uniqstr>
  BRACKETED_ID ID ID_COLON
  PERCENT_ERROR_VERBOSE PERCENT_FILE_PREFIX PERCENT_FLAG PERCENT_NAME_PREFIX
  PERCENT_PURE_PARSER
  TAG tag tag.opt variable
%printer { fputs ($$, yyo); } <uniqstr>
%printer { fprintf (yyo, "[%s]", $$); } BRACKETED_ID
%printer { fprintf (yyo, "%s:", $$); } ID_COLON
%printer { fprintf (yyo, "%%%s", $$); } PERCENT_FLAG
%printer { fprintf (yyo, "<%s>", $$); } TAG tag

%token <int> INT "integer"
%printer { fprintf (yyo, "%d", $$); } <int>

%type <symbol*> id id_colon string_as_id symbol token_decl token_decl_for_prec
%printer { fprintf (yyo, "%s", $$ ? $$->tag : "<NULL>"); } <symbol*>
%printer { fprintf (yyo, "%s:", $$->tag); } id_colon

%type <assoc> precedence_declarator

%destructor { symbol_list_free ($$); } <symbol_list*>
%printer { symbol_list_syms_print ($$, yyo); } <symbol_list*>

%type <named_ref*> named_ref.opt

/*---------.
| %param.  |
`---------*/
%code requires
{
  typedef enum
  {
    param_none   = 0,
    param_lex    = 1 << 0,
    param_parse  = 1 << 1,
    param_both   = param_lex | param_parse
  } param_type;
};
%code
{
  /** Add a lex-param and/or a parse-param.
   *
   * \param type  where to push this formal argument.
   * \param decl  the formal argument.  Destroyed.
   * \param loc   the location in the source.
   */
  static void add_param (param_type type, char *decl, location loc);
  static param_type current_param = param_none;
};
%token <param_type> PERCENT_PARAM "%param";
%printer
{
  switch ($$)
    {
#define CASE(In, Out)                                           \
      case param_ ## In: fputs ("%" #Out, yyo); break
      CASE (lex,   lex-param);
      CASE (parse, parse-param);
      CASE (both,  param);
#undef CASE
      case param_none: aver (false); break;
    }
} <param_type>;


                     /*==========\
                     | Grammar.  |
                     \==========*/
%%

input:
  prologue_declarations "%%" grammar epilogue.opt
;


        /*------------------------------------.
        | Declarations: before the first %%.  |
        `------------------------------------*/

prologue_declarations:
  %empty
| prologue_declarations prologue_declaration
;

prologue_declaration:
  grammar_declaration
| "%{...%}"
    {
      muscle_code_grow (union_seen ? "post_prologue" : "pre_prologue",
                        translate_code ($1, @1, true), @1);
      code_scanner_last_string_free ();
    }
| "%<flag>"
    {
      muscle_percent_define_ensure ($1, @1, true);
    }
| "%define" variable value
    {
      muscle_percent_define_insert ($2, @$, $3.kind, $3.chars,
                                    MUSCLE_PERCENT_DEFINE_GRAMMAR_FILE);
    }
| "%defines"                       { defines_flag = true; }
| "%defines" STRING
    {
      defines_flag = true;
      spec_header_file = xstrdup ($2);
    }
| "%error-verbose"                 { handle_error_verbose (&@$, $1); }
| "%expect" INT                    { expected_sr_conflicts = $2; }
| "%expect-rr" INT                 { expected_rr_conflicts = $2; }
| "%file-prefix" STRING            { handle_file_prefix (&@$, &@1, $1, $2); }
| "%glr-parser"
    {
      nondeterministic_parser = true;
      glr_parser = true;
    }
| "%initial-action" "{...}"
    {
      muscle_code_grow ("initial_action", translate_code ($2, @2, false), @2);
      code_scanner_last_string_free ();
    }
| "%language" STRING            { language_argmatch ($2, grammar_prio, @1); }
| "%name-prefix" STRING         { handle_name_prefix (&@$, $1, $2); }
| "%no-lines"                   { no_lines_flag = true; }
| "%nondeterministic-parser"    { nondeterministic_parser = true; }
| "%output" STRING              { spec_outfile = $2; }
| "%param" { current_param = $1; } params { current_param = param_none; }
| "%pure-parser"                { handle_pure_parser (&@$, $1); }
| "%require" STRING             { handle_require (&@2, $2); }
| "%skeleton" STRING            { handle_skeleton (&@2, $2); }
| "%token-table"                { token_table_flag = true; }
| "%verbose"                    { report_flag |= report_states; }
| "%yacc"                       { handle_yacc (&@$); }
| error ";"                     { current_class = unknown_sym; yyerrok; }
| /*FIXME: Err?  What is this horror doing here? */ ";"
;

params:
   params "{...}"  { add_param (current_param, $2, @2); }
| "{...}"          { add_param (current_param, $1, @1); }
;


/*----------------------.
| grammar_declaration.  |
`----------------------*/

grammar_declaration:
  symbol_declaration
| "%start" symbol
    {
      grammar_start_symbol_set ($2, @2);
    }
| code_props_type "{...}" generic_symlist
    {
      code_props code;
      code_props_symbol_action_init (&code, $2, @2);
      code_props_translate_code (&code);
      {
        for (symbol_list *list = $3; list; list = list->next)
          symbol_list_code_props_set (list, $1, &code);
        symbol_list_free ($3);
      }
    }
| "%default-prec"
    {
      default_prec = true;
    }
| "%no-default-prec"
    {
      default_prec = false;
    }
| "%code" "{...}"
    {
      /* Do not invoke muscle_percent_code_grow here since it invokes
         muscle_user_name_list_grow.  */
      muscle_code_grow ("percent_code()",
                        translate_code_braceless ($2, @2), @2);
      code_scanner_last_string_free ();
    }
| "%code" ID "{...}"
    {
      muscle_percent_code_grow ($2, @2, translate_code_braceless ($3, @3), @3);
      code_scanner_last_string_free ();
    }
;

%type <code_props_type> code_props_type;
%printer { fprintf (yyo, "%s", code_props_type_string ($$)); } <code_props_type>;
code_props_type:
  "%destructor"  { $$ = destructor; }
| "%printer"     { $$ = printer; }
;

/*---------.
| %union.  |
`---------*/

%token PERCENT_UNION "%union";

union_name:
  %empty {}
| ID     { muscle_percent_define_insert ("api.value.union.name",
                                         @1, muscle_keyword, $1,
                                         MUSCLE_PERCENT_DEFINE_GRAMMAR_FILE); }
;

grammar_declaration:
  "%union" union_name "{...}"
    {
      union_seen = true;
      muscle_code_grow ("union_members", translate_code_braceless ($3, @3), @3);
      code_scanner_last_string_free ();
    }
;


%type <symbol_list*> nterm_decls symbol_decls symbol_decl.1
      token_decls token_decls_for_prec
      token_decl.1 token_decl_for_prec.1;
symbol_declaration:
  "%nterm" { current_class = nterm_sym; } nterm_decls[syms]
    {
      current_class = unknown_sym;
      symbol_list_free ($syms);
    }
| "%token" { current_class = token_sym; } token_decls[syms]
    {
      current_class = unknown_sym;
      symbol_list_free ($syms);
    }
| "%type" symbol_decls[syms]
    {
      symbol_list_free ($syms);
    }
| precedence_declarator token_decls_for_prec[syms]
    {
      ++current_prec;
      for (symbol_list *list = $syms; list; list = list->next)
        symbol_precedence_set (list->content.sym, current_prec, $1, @1);
      symbol_list_free ($syms);
    }
;

precedence_declarator:
  "%left"       { $$ = left_assoc; }
| "%right"      { $$ = right_assoc; }
| "%nonassoc"   { $$ = non_assoc; }
| "%precedence" { $$ = precedence_assoc; }
;

tag.opt:
  %empty { $$ = NULL; }
| TAG    { $$ = $1; }
;

%type <symbol_list*> generic_symlist generic_symlist_item;
generic_symlist:
  generic_symlist_item
| generic_symlist generic_symlist_item   { $$ = symbol_list_append ($1, $2); }
;

generic_symlist_item:
  symbol    { $$ = symbol_list_sym_new ($1, @1); }
| tag       { $$ = symbol_list_type_new ($1, @1); }
;

tag:
  TAG
| "<*>" { $$ = uniqstr_new ("*"); }
| "<>"  { $$ = uniqstr_new (""); }
;

/*-----------------------.
| nterm_decls (%nterm).  |
`-----------------------*/

// A non empty list of possibly tagged symbols for %nterm.
//
// Can easily be defined like symbol_decls but restricted to ID, but
// using token_decls allows to reudce the number of rules, and also to
// make nicer error messages on "%nterm 'a'" or '%nterm FOO "foo"'.
nterm_decls:
  token_decls
;

/*-----------------------------------.
| token_decls (%token, and %nterm).  |
`-----------------------------------*/

// A non empty list of possibly tagged symbols for %token or %nterm.
token_decls:
  token_decl.1[syms]
    {
      $$ = $syms;
    }
| TAG token_decl.1[syms]
    {
      $$ = symbol_list_type_set ($syms, $TAG, @TAG);
    }
| token_decls TAG token_decl.1[syms]
    {
      $$ = symbol_list_append ($1, symbol_list_type_set ($syms, $TAG, @TAG));
    }
;

// One or more symbol declarations for %token or %nterm.
token_decl.1:
  token_decl                { $$ = symbol_list_sym_new ($1, @1); }
| token_decl.1 token_decl   { $$ = symbol_list_append ($1, symbol_list_sym_new ($2, @2)); }

// One symbol declaration for %token or %nterm.
token_decl:
  id int.opt[num] string_as_id.opt[alias]
    {
      $$ = $id;
      symbol_class_set ($id, current_class, @id, true);
      if (0 <= $num)
        symbol_user_token_number_set ($id, $num, @num);
      if ($alias)
        symbol_make_alias ($id, $alias, @alias);
    }
;

%type <int> int.opt;
int.opt:
  %empty  { $$ = -1; }
| INT
;

/*-------------------------------------.
| token_decls_for_prec (%left, etc.).  |
`-------------------------------------*/

// A non empty list of possibly tagged tokens for precedence declaration.
//
// Similar to %token (token_decls), but in '%left FOO 1 "foo"', it treats
// FOO and "foo" as two different symbols instead of aliasing them.
token_decls_for_prec:
  token_decl_for_prec.1[syms]
    {
      $$ = $syms;
    }
| TAG token_decl_for_prec.1[syms]
    {
      $$ = symbol_list_type_set ($syms, $TAG, @TAG);
    }
| token_decls_for_prec TAG token_decl_for_prec.1[syms]
    {
      $$ = symbol_list_append ($1, symbol_list_type_set ($syms, $TAG, @TAG));
    }
;

// One or more token declarations for precedence declaration.
token_decl_for_prec.1:
  token_decl_for_prec
    { $$ = symbol_list_sym_new ($1, @1); }
| token_decl_for_prec.1 token_decl_for_prec
    { $$ = symbol_list_append ($1, symbol_list_sym_new ($2, @2)); }

// One token declaration for precedence declaration.
token_decl_for_prec:
  id int.opt[num]
    {
      $$ = $id;
      symbol_class_set ($id, token_sym, @id, false);
      if (0 <= $num)
        symbol_user_token_number_set ($id, $num, @num);
    }
| string_as_id
;


/*-----------------------------------.
| symbol_decls (argument of %type).  |
`-----------------------------------*/

// A non empty list of typed symbols (for %type).
symbol_decls:
  symbol_decl.1[syms]
    {
      $$ = $syms;
    }
| TAG symbol_decl.1[syms]
    {
      $$ = symbol_list_type_set ($syms, $TAG, @TAG);
    }
| symbol_decls TAG symbol_decl.1[syms]
    {
      $$ = symbol_list_append ($1, symbol_list_type_set ($syms, $TAG, @TAG));
    }
;

// One or more token declarations (for %type).
symbol_decl.1:
  symbol
    {
      symbol_class_set ($symbol, pct_type_sym, @symbol, false);
      $$ = symbol_list_sym_new ($symbol, @symbol);
    }
  | symbol_decl.1 symbol
    {
      symbol_class_set ($symbol, pct_type_sym, @symbol, false);
      $$ = symbol_list_append ($1, symbol_list_sym_new ($symbol, @symbol));
    }
;

        /*------------------------------------------.
        | The grammar section: between the two %%.  |
        `------------------------------------------*/

grammar:
  rules_or_grammar_declaration
| grammar rules_or_grammar_declaration
;

/* As a Bison extension, one can use the grammar declarations in the
   body of the grammar.  */
rules_or_grammar_declaration:
  rules
| grammar_declaration ";"
| error ";"
    {
      yyerrok;
    }
;

rules:
  id_colon named_ref.opt { current_lhs ($1, @1, $2); } ":" rhses.1
    {
      /* Free the current lhs. */
      current_lhs (0, @1, 0);
    }
;

rhses.1:
  rhs                { grammar_current_rule_end (@rhs); }
| rhses.1 "|" rhs    { grammar_current_rule_end (@rhs); }
| rhses.1 ";"
;

%token PERCENT_EMPTY "%empty";
rhs:
  %empty
    { grammar_current_rule_begin (current_lhs_symbol, current_lhs_loc,
                                  current_lhs_named_ref); }
| rhs symbol named_ref.opt
    { grammar_current_rule_symbol_append ($2, @2, $3); }
| rhs tag.opt "{...}"[act] named_ref.opt[name]
    { grammar_current_rule_action_append ($act, @act, $name, $[tag.opt]); }
| rhs "%?{...}"
    { grammar_current_rule_predicate_append ($2, @2); }
| rhs "%empty"
    { grammar_current_rule_empty_set (@2); }
| rhs "%prec" symbol
    { grammar_current_rule_prec_set ($3, @3); }
| rhs "%dprec" INT
    { grammar_current_rule_dprec_set ($3, @3); }
| rhs "%merge" TAG
    { grammar_current_rule_merge_set ($3, @3); }
| rhs "%expect" INT
    { grammar_current_rule_expect_sr ($3, @3); }
| rhs "%expect-rr" INT
    { grammar_current_rule_expect_rr ($3, @3); }
;

named_ref.opt:
  %empty         { $$ = NULL; }
| BRACKETED_ID   { $$ = named_ref_new ($1, @1); }
;


/*---------------------.
| variable and value.  |
`---------------------*/

variable:
  ID
;

/* Some content or empty by default. */
%code requires {
  #include "muscle-tab.h"
  typedef struct
  {
    char const *chars;
    muscle_kind kind;
  } value_type;
};
%type <value_type> value;
%printer
{
  switch ($$.kind)
    {
    case muscle_code:    fprintf (yyo,  "{%s}",  $$.chars); break;
    case muscle_keyword: fprintf (yyo,   "%s",   $$.chars); break;
    case muscle_string:  fprintf (yyo, "\"%s\"", $$.chars); break;
    }
} <value_type>;

value:
  %empty  { $$.kind = muscle_keyword; $$.chars = ""; }
| ID      { $$.kind = muscle_keyword; $$.chars = $1; }
| STRING  { $$.kind = muscle_string;  $$.chars = $1; }
| "{...}" { $$.kind = muscle_code;    $$.chars = strip_braces ($1); }
;


/*--------------.
| Identifiers.  |
`--------------*/

/* Identifiers are returned as uniqstr values by the scanner.
   Depending on their use, we may need to make them genuine symbols.  */

id:
  ID
    { $$ = symbol_from_uniqstr ($1, @1); }
| CHAR
    {
      const char *var = "api.token.raw";
      if (current_class == nterm_sym)
        {
          complain (&@1, complaint,
                    _("character literals cannot be nonterminals"));
          YYERROR;
        }
      if (muscle_percent_define_ifdef (var))
        {
          int indent = 0;
          complain_indent (&@1, complaint, &indent,
                           _("character literals cannot be used together"
                             " with %s"), var);
          indent += SUB_INDENT;
          location loc = muscle_percent_define_get_loc (var);
          complain_indent (&loc, complaint, &indent,
                           _("definition of %s"), var);
        }
      $$ = symbol_get (char_name ($1), @1);
      symbol_class_set ($$, token_sym, @1, false);
      symbol_user_token_number_set ($$, $1, @1);
    }
;

id_colon:
  ID_COLON { $$ = symbol_from_uniqstr ($1, @1); }
;


symbol:
  id
| string_as_id
;

/* A string used as an ID: quote it.  */
string_as_id:
  STRING
    {
      $$ = symbol_get (quotearg_style (c_quoting_style, $1), @1);
      symbol_class_set ($$, token_sym, @1, false);
    }
;

%type <symbol*> string_as_id.opt;
string_as_id.opt:
  %empty             { $$ = NULL; }
| string_as_id
;

epilogue.opt:
  %empty
| "%%" EPILOGUE
    {
      muscle_code_grow ("epilogue", translate_code ($2, @2, true), @2);
      code_scanner_last_string_free ();
    }
;

%%

/* Return the location of the left-hand side of a rule whose
   right-hand side is RHS[1] ... RHS[N].  Ignore empty nonterminals in
   the right-hand side, and return an empty location equal to the end
   boundary of RHS[0] if the right-hand side is empty.  */

static YYLTYPE
lloc_default (YYLTYPE const *rhs, int n)
{
  YYLTYPE loc;

  /* SGI MIPSpro 7.4.1m miscompiles "loc.start = loc.end = rhs[n].end;".
     The bug is fixed in 7.4.2m, but play it safe for now.  */
  loc.start = rhs[n].end;
  loc.end = rhs[n].end;

  /* Ignore empty nonterminals the start of the right-hand side.
     Do not bother to ignore them at the end of the right-hand side,
     since empty nonterminals have the same end as their predecessors.  */
  for (int i = 1; i <= n; i++)
    if (! equal_boundaries (rhs[i].start, rhs[i].end))
      {
        loc.start = rhs[i].start;
        break;
      }

  return loc;
}

static
char *strip_braces (char *code)
{
  code[strlen (code) - 1] = 0;
  return code + 1;
}

static
char const *
translate_code (char *code, location loc, bool plain)
{
  code_props plain_code;
  if (plain)
    code_props_plain_init (&plain_code, code, loc);
  else
    code_props_symbol_action_init (&plain_code, code, loc);
  code_props_translate_code (&plain_code);
  gram_scanner_last_string_free ();
  return plain_code.code;
}

static
char const *
translate_code_braceless (char *code, location loc)
{
  return translate_code (strip_braces (code), loc, true);
}

static void
add_param (param_type type, char *decl, location loc)
{
  static char const alphanum[26 + 26 + 1 + 10 + 1] =
    "abcdefghijklmnopqrstuvwxyz"
    "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
    "_"
    "0123456789";

  char const *name_start = NULL;
  {
    char *p;
    /* Stop on last actual character.  */
    for (p = decl; p[1]; p++)
      if ((p == decl
           || ! memchr (alphanum, p[-1], sizeof alphanum - 1))
          && memchr (alphanum, p[0], sizeof alphanum - 10 - 1))
        name_start = p;

    /* Strip the surrounding '{' and '}', and any blanks just inside
       the braces.  */
    --p;
    while (c_isspace ((unsigned char) *p))
      --p;
    p[1] = '\0';
    ++decl;
    while (c_isspace ((unsigned char) *decl))
      ++decl;
  }

  if (! name_start)
    complain (&loc, complaint, _("missing identifier in parameter declaration"));
  else
    {
      char *name = xmemdup0 (name_start, strspn (name_start, alphanum));
      if (type & param_lex)
        muscle_pair_list_grow ("lex_param", decl, name);
      if (type & param_parse)
        muscle_pair_list_grow ("parse_param", decl, name);
      free (name);
    }

  gram_scanner_last_string_free ();
}


static void
handle_error_verbose (location const *loc, char const *directive)
{
  bison_directive (loc, directive);
  muscle_percent_define_insert (directive, *loc, muscle_keyword, "",
                                MUSCLE_PERCENT_DEFINE_GRAMMAR_FILE);
}


static void
handle_file_prefix (location const *loc,
                    location const *dir_loc,
                    char const *directive, char const *value)
{
  bison_directive (loc, directive);
  bool warned = false;

  if (location_empty (spec_file_prefix_loc))
    {
      spec_file_prefix_loc = *loc;
      spec_file_prefix = value;
    }
  else
    {
      duplicate_directive (directive, spec_file_prefix_loc, *loc);
      warned = true;
    }

  if (!warned
      && STRNEQ (directive, "%file-prefix"))
    deprecated_directive (dir_loc, directive, "%file-prefix");
}


static void
handle_name_prefix (location const *loc,
                    char const *directive, char const *value)
{
  bison_directive (loc, directive);

  char buf1[1024];
  size_t len1 = sizeof (buf1);
  char *old = asnprintf (buf1, &len1, "%s\"%s\"", directive, value);
  if (!old)
    xalloc_die ();

  if (location_empty (spec_name_prefix_loc))
    {
      spec_name_prefix = value;
      spec_name_prefix_loc = *loc;

      char buf2[1024];
      size_t len2 = sizeof (buf2);
      char *new = asnprintf (buf2, &len2, "%%define api.prefix {%s}", value);
      if (!new)
        xalloc_die ();
      deprecated_directive (loc, old, new);
      if (new != buf2)
        free (new);
    }
  else
    duplicate_directive (old, spec_file_prefix_loc, *loc);

  if (old != buf1)
    free (old);
}


static void
handle_pure_parser (location const *loc, char const *directive)
{
  bison_directive (loc, directive);
  deprecated_directive (loc, directive, "%define api.pure");
  muscle_percent_define_insert ("api.pure", *loc, muscle_keyword, "",
                                MUSCLE_PERCENT_DEFINE_GRAMMAR_FILE);
}


/* Convert VERSION into an int (MAJOR * 100 + MINOR).  Return -1 on
   errors.

   Changes of behavior are only on minor version changes, so "3.0.5"
   is the same as "3.0": 300. */
static int
str_to_version (char const *version)
{
  IGNORE_TYPE_LIMITS_BEGIN
  int res = 0;
  errno = 0;
  char *cp = NULL;
  long major = strtol (version, &cp, 10);
  if (errno || cp == version || *cp != '.' || major < 0
      || INT_MULTIPLY_WRAPV (major, 100, &res))
    return -1;

  ++cp;
  char *cp1 = NULL;
  long minor = strtol (cp, &cp1, 10);
  if (errno || cp1 == cp || (*cp1 != '\0' && *cp1 != '.')
      || ! (0 <= minor && minor < 100)
      || INT_ADD_WRAPV (minor, res, &res))
    return -1;

  IGNORE_TYPE_LIMITS_END
  return res;
}


static void
handle_require (location const *loc, char const *version)
{
  required_version = str_to_version (version);
  if (required_version == -1)
    {
      complain (loc, complaint, _("invalid version requirement: %s"),
                version);
      required_version = 0;
      return;
    }

  /* Pretend to be at least 3.5, to check features published in that
     version while developping it.  */
  const char* api_version = "3.5";
  const char* package_version =
    0 < strverscmp (api_version, PACKAGE_VERSION)
    ? api_version : PACKAGE_VERSION;
  if (0 < strverscmp (version, package_version))
    {
      complain (loc, complaint, _("require bison %s, but have %s"),
                version, package_version);
      exit (EX_MISMATCH);
    }
}

static void
handle_skeleton (location const *loc, char const *skel)
{
  char const *skeleton_user = skel;
  if (strchr (skeleton_user, '/'))
    {
      size_t dir_length = strlen (grammar_file);
      while (dir_length && grammar_file[dir_length - 1] != '/')
        --dir_length;
      while (dir_length && grammar_file[dir_length - 1] == '/')
        --dir_length;
      char *skeleton_build =
        xmalloc (dir_length + 1 + strlen (skeleton_user) + 1);
      if (dir_length > 0)
        {
          memcpy (skeleton_build, grammar_file, dir_length);
          skeleton_build[dir_length++] = '/';
        }
      strcpy (skeleton_build + dir_length, skeleton_user);
      skeleton_user = uniqstr_new (skeleton_build);
      free (skeleton_build);
    }
  skeleton_arg (skeleton_user, grammar_prio, *loc);
}


static void
handle_yacc (location const *loc)
{
  const char *directive = "%yacc";
  bison_directive (loc, directive);
  if (location_empty (yacc_loc))
    yacc_loc = *loc;
  else
    duplicate_directive (directive, yacc_loc, *loc);
}


static void
gram_error (location const *loc, char const *msg)
{
  complain (loc, complaint, "%s", msg);
}

static char const *
char_name (char c)
{
  if (c == '\'')
    return "'\\''";
  else
    {
      char buf[4];
      buf[0] = '\''; buf[1] = c; buf[2] = '\''; buf[3] = '\0';
      return quotearg_style (escape_quoting_style, buf);
    }
}

static
void
current_lhs (symbol *sym, location loc, named_ref *ref)
{
  current_lhs_symbol = sym;
  current_lhs_loc = loc;
  if (sym)
    symbol_location_as_lhs_set (sym, loc);
  /* In order to simplify memory management, named references for lhs
     are always assigned by deep copy into the current symbol_list
     node.  This is because a single named-ref in the grammar may
     result in several uses when the user factors lhs between several
     rules using "|".  Therefore free the parser's original copy.  */
  free (current_lhs_named_ref);
  current_lhs_named_ref = ref;
}

static void tron (FILE *yyo)
{
  begin_use_class ("value", yyo);
}

static void troff (FILE *yyo)
{
  end_use_class ("value", yyo);
}