Allow specification of semantic predicates.

[bison.git] / src / output.c

diff --git a/src/output.c b/src/output.c
index b3e7c6c497c66b3b3d22b0563b986b2071e93267..6b29e5c056cd337fbe045ddce49b5e147b054728 100644 (file)
--- a/src/output.c
+++ b/src/output.c
@@ -1,24 +1,22 @@
 /* Output the generated parsing program for Bison.
 
    Copyright (C) 1984, 1986, 1989, 1992, 2000, 2001, 2002, 2003, 2004,
 /* Output the generated parsing program for Bison.
 
    Copyright (C) 1984, 1986, 1989, 1992, 2000, 2001, 2002, 2003, 2004,

-   2005, 2006, 2007 Free Software Foundation, Inc.
+   2005, 2006, 2007, 2008, 2009, 2010 Free Software Foundation, Inc.

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

-   Bison 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.
+   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.

 
 

-   Bison 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.
+   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
 
    You should have received a copy of the GNU General Public License

-   along with Bison; see the file COPYING.  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/>.  */

 
 #include <config.h>
 #include "system.h"
 
 #include <config.h>
 #include "system.h"


@@ -26,15 +24,16 @@
 #include <configmake.h>
 #include <error.h>
 #include <get-errno.h>
 #include <configmake.h>
 #include <error.h>
 #include <get-errno.h>

+#include <pipe.h>

 #include <quotearg.h>
 #include <quotearg.h>

-#include <subpipe.h>

 #include <timevar.h>
 #include <timevar.h>

+#include <wait-process.h>

 
 #include "complain.h"
 #include "files.h"
 #include "getargs.h"
 #include "gram.h"
 
 #include "complain.h"
 #include "files.h"
 #include "getargs.h"
 #include "gram.h"

-#include "muscle_tab.h"
+#include "muscle-tab.h"

 #include "output.h"
 #include "reader.h"
 #include "scan-code.h"    /* max_left_semantic_context */
 #include "output.h"
 #include "reader.h"
 #include "scan-code.h"    /* max_left_semantic_context */


@@ -42,6 +41,7 @@
 #include "symtab.h"
 #include "tables.h"
 
 #include "symtab.h"
 #include "tables.h"
 

+# define ARRAY_CARDINALITY(Array) (sizeof (Array) / sizeof *(Array))

 
 static struct obstack format_obstack;
 
 
 static struct obstack format_obstack;
 


@@ -106,7 +106,6 @@ GENERATE_MUSCLE_INSERT_TABLE(muscle_insert_int_table, int)
 GENERATE_MUSCLE_INSERT_TABLE(muscle_insert_base_table, base_number)
 GENERATE_MUSCLE_INSERT_TABLE(muscle_insert_rule_number_table, rule_number)
 GENERATE_MUSCLE_INSERT_TABLE(muscle_insert_symbol_number_table, symbol_number)
 GENERATE_MUSCLE_INSERT_TABLE(muscle_insert_base_table, base_number)
 GENERATE_MUSCLE_INSERT_TABLE(muscle_insert_rule_number_table, rule_number)
 GENERATE_MUSCLE_INSERT_TABLE(muscle_insert_symbol_number_table, symbol_number)

-GENERATE_MUSCLE_INSERT_TABLE(muscle_insert_item_number_table, item_number)

 GENERATE_MUSCLE_INSERT_TABLE(muscle_insert_state_number_table, state_number)
 
 
 GENERATE_MUSCLE_INSERT_TABLE(muscle_insert_state_number_table, state_number)
 
 


@@ -145,6 +144,7 @@ prepare_symbols (void)
   MUSCLE_INSERT_BOOL ("token_table", token_table_flag);
   MUSCLE_INSERT_INT ("tokens_number", ntokens);
   MUSCLE_INSERT_INT ("nterms_number", nvars);
   MUSCLE_INSERT_BOOL ("token_table", token_table_flag);
   MUSCLE_INSERT_INT ("tokens_number", ntokens);
   MUSCLE_INSERT_INT ("nterms_number", nvars);

+  MUSCLE_INSERT_INT ("symbols_number", nsyms);

   MUSCLE_INSERT_INT ("undef_token_number", undeftoken->number);
   MUSCLE_INSERT_INT ("user_token_number_max", max_user_token_number);
 
   MUSCLE_INSERT_INT ("undef_token_number", undeftoken->number);
   MUSCLE_INSERT_INT ("user_token_number_max", max_user_token_number);
 


@@ -158,9 +158,12 @@ prepare_symbols (void)
     int i;
     /* We assume that the table will be output starting at column 2. */
     int j = 2;
     int i;
     /* We assume that the table will be output starting at column 2. */
     int j = 2;

+    struct quoting_options *qo = clone_quoting_options (0);
+    set_quoting_style (qo, c_quoting_style);
+    set_quoting_flags (qo, QA_SPLIT_TRIGRAPHS);

     for (i = 0; i < nsyms; i++)
       {
     for (i = 0; i < nsyms; i++)
       {

-       char const *cp = quotearg_style (c_quoting_style, symbols[i]->tag);
+       char *cp = quotearg_alloc (symbols[i]->tag, -1, qo);

        /* Width of the next token, including the two quotes, the
           comma and the space.  */
        int width = strlen (cp) + 2;
        /* Width of the next token, including the two quotes, the
           comma and the space.  */
        int width = strlen (cp) + 2;


@@ -174,9 +177,11 @@ prepare_symbols (void)
        if (i)
          obstack_1grow (&format_obstack, ' ');
        MUSCLE_OBSTACK_SGROW (&format_obstack, cp);
        if (i)
          obstack_1grow (&format_obstack, ' ');
        MUSCLE_OBSTACK_SGROW (&format_obstack, cp);

+        free (cp);

        obstack_1grow (&format_obstack, ',');
        j += width;
       }
        obstack_1grow (&format_obstack, ',');
        j += width;
       }

+    free (qo);

     obstack_sgrow (&format_obstack, " ]b4_null[");
 
     /* Finish table and store. */
     obstack_sgrow (&format_obstack, " ]b4_null[");
 
     /* Finish table and store. */


@@ -197,60 +202,48 @@ prepare_symbols (void)
 }
 
 
 }
 
 

-/*-------------------------------------------------------------.
-| Prepare the muscles related to the rules: rhs, prhs, r1, r2, |
-| rline, dprec, merger.                                        |
-`-------------------------------------------------------------*/
+/*----------------------------------------------------------------.
+| Prepare the muscles related to the rules: r1, r2, rline, dprec, |
+| merger, immediate.                                              |
+`----------------------------------------------------------------*/

 
 static void
 prepare_rules (void)
 {
 
 static void
 prepare_rules (void)
 {

-  rule_number r;
-  unsigned int i = 0;
-  item_number *rhs = xnmalloc (nritems, sizeof *rhs);
-  unsigned int *prhs = xnmalloc (nrules, sizeof *prhs);

   unsigned int *rline = xnmalloc (nrules, sizeof *rline);
   symbol_number *r1 = xnmalloc (nrules, sizeof *r1);
   unsigned int *r2 = xnmalloc (nrules, sizeof *r2);
   int *dprec = xnmalloc (nrules, sizeof *dprec);
   int *merger = xnmalloc (nrules, sizeof *merger);
   unsigned int *rline = xnmalloc (nrules, sizeof *rline);
   symbol_number *r1 = xnmalloc (nrules, sizeof *r1);
   unsigned int *r2 = xnmalloc (nrules, sizeof *r2);
   int *dprec = xnmalloc (nrules, sizeof *dprec);
   int *merger = xnmalloc (nrules, sizeof *merger);

+  int *immediate = xnmalloc (nrules, sizeof *immediate);

 
 

+  rule_number r;

   for (r = 0; r < nrules; ++r)
     {
   for (r = 0; r < nrules; ++r)
     {

-      item_number *rhsp = NULL;
-      /* Index of rule R in RHS. */
-      prhs[r] = i;
-      /* RHS of the rule R. */
-      for (rhsp = rules[r].rhs; *rhsp >= 0; ++rhsp)
-       rhs[i++] = *rhsp;

       /* LHS of the rule R. */
       r1[r] = rules[r].lhs->number;
       /* Length of rule R's RHS. */
       /* LHS of the rule R. */
       r1[r] = rules[r].lhs->number;
       /* Length of rule R's RHS. */

-      r2[r] = i - prhs[r];
-      /* Separator in RHS. */
-      rhs[i++] = -1;
+      r2[r] = rule_rhs_length(&rules[r]);

       /* Line where rule was defined. */
       rline[r] = rules[r].location.start.line;
       /* Dynamic precedence (GLR).  */
       dprec[r] = rules[r].dprec;
       /* Merger-function index (GLR).  */
       merger[r] = rules[r].merger;
       /* Line where rule was defined. */
       rline[r] = rules[r].location.start.line;
       /* Dynamic precedence (GLR).  */
       dprec[r] = rules[r].dprec;
       /* Merger-function index (GLR).  */
       merger[r] = rules[r].merger;

+      /* Immediate reduction flags (GLR).  */
+      immediate[r] = rules[r].is_predicate;

     }
     }

-  aver (i == nritems);

 
 

-  muscle_insert_item_number_table ("rhs", rhs, ritem[0], 1, nritems);
-  muscle_insert_unsigned_int_table ("prhs", prhs, 0, 0, nrules);

   muscle_insert_unsigned_int_table ("rline", rline, 0, 0, nrules);
   muscle_insert_symbol_number_table ("r1", r1, 0, 0, nrules);
   muscle_insert_unsigned_int_table ("r2", r2, 0, 0, nrules);
   muscle_insert_int_table ("dprec", dprec, 0, 0, nrules);
   muscle_insert_int_table ("merger", merger, 0, 0, nrules);
   muscle_insert_unsigned_int_table ("rline", rline, 0, 0, nrules);
   muscle_insert_symbol_number_table ("r1", r1, 0, 0, nrules);
   muscle_insert_unsigned_int_table ("r2", r2, 0, 0, nrules);
   muscle_insert_int_table ("dprec", dprec, 0, 0, nrules);
   muscle_insert_int_table ("merger", merger, 0, 0, nrules);

+  muscle_insert_int_table ("immediate", immediate, 0, 0, nrules);

 
   MUSCLE_INSERT_INT ("rules_number", nrules);
   MUSCLE_INSERT_INT ("max_left_semantic_context", max_left_semantic_context);
 
 
   MUSCLE_INSERT_INT ("rules_number", nrules);
   MUSCLE_INSERT_INT ("max_left_semantic_context", max_left_semantic_context);
 

-  free (rhs);
-  free (prhs);

   free (rline);
   free (r1);
   free (r2);
   free (rline);
   free (r1);
   free (r2);


@@ -279,6 +272,73 @@ prepare_states (void)
 }
 
 
 }
 
 

+/*-------------------------------------------------------.
+| Compare two symbols by type-name, and then by number.  |
+`-------------------------------------------------------*/
+
+static int
+symbol_type_name_cmp (const symbol **lhs, const symbol **rhs)
+{
+  int res = UNIQSTR_CMP((*lhs)->type_name, (*rhs)->type_name);
+  if (res)
+    return res;
+  return (*lhs)->number - (*rhs)->number;
+}
+
+
+/*----------------------------------------------------------------.
+| Return a (malloc'ed) table of the symbols sorted by type-name.  |
+`----------------------------------------------------------------*/
+
+static symbol **
+symbols_by_type_name (void)
+{
+  typedef int (*qcmp_type) (const void *, const void *);
+  symbol **res = xmemdup (symbols, nsyms * sizeof *res);
+  qsort (res, nsyms, sizeof *res, (qcmp_type) &symbol_type_name_cmp);
+  return res;
+}
+
+
+/*------------------------------------------------------------------.
+| Define b4_type_names, which is a list of (lists of the numbers of |
+| symbols with same type-name).                                     |
+`------------------------------------------------------------------*/
+
+static void
+type_names_output (FILE *out)
+{
+  int i;
+  symbol **syms = symbols_by_type_name ();
+  fputs ("m4_define([b4_type_names],\n[", out);
+  for (i = 0; i < nsyms; /* nothing */)
+    {
+      // The index of the first symbol of the current type-name.
+      int i0 = i;
+      fputs (i ? ",\n[" : "[", out);
+      for (; i < nsyms && syms[i]->type_name == syms[i0]->type_name; ++i)
+        fprintf (out, "%s%d", i != i0 ? ", " : "", syms[i]->number);
+      fputs ("]", out);
+    }
+  fputs ("])\n\n", out);
+  free (syms);
+}
+
+
+/*-------------------------------------.
+| The list of all the symbol numbers.  |
+`-------------------------------------*/
+
+static void
+symbol_numbers_output (FILE *out)
+{
+  int i;
+  fputs ("m4_define([b4_symbol_numbers],\n[", out);
+  for (i = 0; i < nsyms; ++i)
+    fprintf (out, "%s[%d]", i ? ", " : "", i);
+  fputs ("])\n\n", out);
+}
+

 
 /*---------------------------------.
 | Output the user actions to OUT.  |
 
 /*---------------------------------.
 | Output the user actions to OUT.  |


@@ -293,17 +353,18 @@ user_actions_output (FILE *out)
   for (r = 0; r < nrules; ++r)
     if (rules[r].action)
       {
   for (r = 0; r < nrules; ++r)
     if (rules[r].action)
       {

-       fprintf (out, "b4_case(%d, [b4_syncline(%d, ", r + 1,
-                rules[r].action_location.start.line);
+       fprintf (out, "b4_%scase(%d, [b4_syncline(%d, ",
+                rules[r].is_predicate ? "predicate_" : "",
+                r + 1, rules[r].action_location.start.line);

        escaped_output (out, rules[r].action_location.start.file);
        fprintf (out, ")\n[    %s]])\n\n", rules[r].action);
       }
   fputs ("])\n\n", out);
 }
 
        escaped_output (out, rules[r].action_location.start.file);
        fprintf (out, ")\n[    %s]])\n\n", rules[r].action);
       }
   fputs ("])\n\n", out);
 }
 

-/*--------------------------------------.
-| Output the merge functions to OUT.   |
-`--------------------------------------*/
+/*------------------------------------.
+| Output the merge functions to OUT.  |
+`------------------------------------*/

 
 static void
 merger_output (FILE *out)
 
 static void
 merger_output (FILE *out)


@@ -324,88 +385,110 @@ merger_output (FILE *out)
   fputs ("]])\n\n", out);
 }
 
   fputs ("]])\n\n", out);
 }
 

-/*--------------------------------------.
-| Output the tokens definition to OUT.  |
-`--------------------------------------*/
+
+/*---------------------------------------------.
+| Prepare the muscles for symbol definitions.  |
+`---------------------------------------------*/

 
 static void
 
 static void

-token_definitions_output (FILE *out)
+prepare_symbol_definitions (void)

 {
   int i;
 {
   int i;

-  char const *sep = "";
-
-  fputs ("m4_define([b4_tokens], \n[", out);
-  for (i = 0; i < ntokens; ++i)
+  for (i = 0; i < nsyms; ++i)

     {
       symbol *sym = symbols[i];
     {
       symbol *sym = symbols[i];

-      int number = sym->user_token_number;
-
-      /* At this stage, if there are literal aliases, they are part of
-        SYMBOLS, so we should not find symbols which are the aliases
-        here.  */
-      aver (number != USER_NUMBER_ALIAS);
-
-      /* Skip error token.  */
-      if (sym == errtoken)
-       continue;
-
-      /* If this string has an alias, then it is necessarily the alias
-        which is to be output.  */
-      if (sym->alias)
-       sym = sym->alias;
-
-      /* Don't output literal chars or strings (when defined only as a
-        string).  Note that must be done after the alias resolution:
-        think about `%token 'f' "f"'.  */
-      if (sym->tag[0] == '\'' || sym->tag[0] == '\"')
-       continue;
-
-      /* Don't #define nonliteral tokens whose names contain periods
-        or '$' (as does the default value of the EOF token).  */
-      if (strchr (sym->tag, '.') || strchr (sym->tag, '$'))
-       continue;
-
-      fprintf (out, "%s[[[%s]], %d]",
-              sep, sym->tag, number);
-      sep = ",\n";
+      const char *key;
+      const char *value;
+
+#define SET_KEY(Entry)                                                  \
+      obstack_fgrow2 (&format_obstack, "symbol(%d, %s)", i, Entry);     \
+      obstack_1grow (&format_obstack, 0);                               \
+      key = obstack_finish (&format_obstack);
+
+      // Whether the symbol has an identifier.
+      value = symbol_id_get (sym);
+      SET_KEY("has_id");
+      MUSCLE_INSERT_INT (key, !!value);
+
+      // Its identifier.
+      SET_KEY("id");
+      MUSCLE_INSERT_STRING (key, value ? value : "");
+
+      // Its tag.  Typically for documentation purpose.
+      SET_KEY("tag");
+      MUSCLE_INSERT_STRING (key, sym->tag);
+
+      SET_KEY("user_number");
+      MUSCLE_INSERT_INT (key, sym->user_token_number);
+
+      SET_KEY("is_token");
+      MUSCLE_INSERT_INT (key,
+                         i < ntokens && sym != errtoken && sym != undeftoken);
+
+      SET_KEY("number");
+      MUSCLE_INSERT_INT (key, sym->number);
+
+      SET_KEY("has_type");
+      MUSCLE_INSERT_INT (key, !!sym->type_name);
+
+      SET_KEY("type");
+      MUSCLE_INSERT_STRING (key, sym->type_name ? sym->type_name : "");
+
+#define CODE_PROP(PropName)                                             \
+      do {                                                              \
+        code_props const *p = symbol_ ## PropName ## _get (sym);        \
+        SET_KEY("has_" #PropName);                                      \
+        MUSCLE_INSERT_INT (key, !!p->code);                             \
+                                                                        \
+        if (p->code)                                                    \
+          {                                                             \
+            SET_KEY(#PropName "_file");                                 \
+            MUSCLE_INSERT_STRING (key, p->location.start.file);         \
+                                                                        \
+            SET_KEY(#PropName "_line");                                 \
+            MUSCLE_INSERT_INT (key, p->location.start.line);            \
+                                                                        \
+            SET_KEY(#PropName);                                         \
+            MUSCLE_INSERT_STRING_RAW (key, p->code);                    \
+          }                                                             \
+      } while (0)
+
+      CODE_PROP(destructor);
+      CODE_PROP(printer);
+#undef CODE_PROP
+#undef SET_KEY

     }
     }

-  fputs ("])\n\n", out);

 }
 
 
 }
 
 

-/*---------------------------------------------------.
-| Output the symbol destructors or printers to OUT.  |
-`---------------------------------------------------*/
+/*--------------------------------------.
+| Output the tokens definition to OUT.  |
+`--------------------------------------*/

 
 static void
 
 static void

-symbol_code_props_output (FILE *out, char const *what,
-                          code_props const *(*get)(symbol const *))
+token_definitions_output (FILE *out)

 {
   int i;
   char const *sep = "";
 
 {
   int i;
   char const *sep = "";
 

-  fputs ("m4_define([b4_symbol_", out);
-  fputs (what, out);
-  fputs ("], \n[", out);
-  for (i = 0; i < nsyms; ++i)
+  fputs ("m4_define([b4_tokens], \n[", out);
+  for (i = 0; i < ntokens; ++i)

     {
       symbol *sym = symbols[i];
     {
       symbol *sym = symbols[i];

-      char const *code = (*get) (sym)->code;
-      if (code)
+      int number = sym->user_token_number;
+      uniqstr id = symbol_id_get (sym);
+
+      /* At this stage, if there are literal string aliases, they are
+         part of SYMBOLS, so we should not find their aliased symbols
+         here.  */
+      aver (number != USER_NUMBER_HAS_STRING_ALIAS);
+
+      /* Skip error token and tokens without identifier.  */
+      if (sym != errtoken && id)

         {
         {

-          location loc = (*get) (sym)->location;
-          /* Filename, lineno,
-             Symbol-name, Symbol-number,
-             code, optional typename.  */
-          fprintf (out, "%s[", sep);
+          fprintf (out, "%s[[[%s]], %d]",
+                   sep, id, number);

           sep = ",\n";
           sep = ",\n";

-          escaped_output (out, loc.start.file);
-          fprintf (out, ", %d, ", loc.start.line);
-          escaped_output (out, sym->tag);
-          fprintf (out, ", %d, [[%s]]", sym->number, code);
-          if (sym->type_name)
-            fprintf (out, ", [[%s]]", sym->type_name);
-          fputc (']', out);

         }
     }
   fputs ("])\n\n", out);
         }
     }
   fputs ("])\n\n", out);


@@ -459,6 +542,23 @@ prepare_actions (void)
                                    0, 1, conflict_list_cnt);
 }
 
                                    0, 1, conflict_list_cnt);
 }
 

+
+/*--------------------------------------------.
+| Output the definitions of all the muscles.  |
+`--------------------------------------------*/
+
+static void
+muscles_output (FILE *out)
+{
+  fputs ("m4_init()\n", out);
+  merger_output (out);
+  symbol_numbers_output (out);
+  token_definitions_output (out);
+  type_names_output (out);
+  user_actions_output (out);
+  // Must be last.
+  muscles_m4_output (out);
+}

 \f
 /*---------------------------.
 | Call the skeleton parser.  |
 \f
 /*---------------------------.
 | Call the skeleton parser.  |


@@ -468,15 +568,11 @@ static void
 output_skeleton (void)
 {
   FILE *in;
 output_skeleton (void)
 {
   FILE *in;

-  FILE *out;

   int filter_fd[2];
   int filter_fd[2];

-  char const *argv[7];
+  char const *argv[10];

   pid_t pid;
 
   pid_t pid;
 

-  /* Compute the names of the package data dir and skeleton file.
-     Test whether m4sugar.m4 is readable, to check for proper
-     installation.  A faulty installation can cause deadlock, so a
-     cheap sanity check is worthwhile.  */
+  /* Compute the names of the package data dir and skeleton files.  */

   char const m4sugar[] = "m4sugar/m4sugar.m4";
   char const m4bison[] = "bison.m4";
   char *full_m4sugar;
   char const m4sugar[] = "m4sugar/m4sugar.m4";
   char const m4bison[] = "bison.m4";
   char *full_m4sugar;


@@ -484,7 +580,7 @@ output_skeleton (void)
   char *full_skeleton;
   char const *p;
   char const *m4 = (p = getenv ("M4")) ? p : M4;
   char *full_skeleton;
   char const *p;
   char const *m4 = (p = getenv ("M4")) ? p : M4;

-  char const *pkgdatadir = (p = getenv ("BISON_PKGDATADIR")) ? p : PKGDATADIR;
+  char const *pkgdatadir = compute_pkgdatadir ();

   size_t skeleton_size = strlen (skeleton) + 1;
   size_t pkgdatadirlen = strlen (pkgdatadir);
   while (pkgdatadirlen && pkgdatadir[pkgdatadirlen - 1] == '/')
   size_t skeleton_size = strlen (skeleton) + 1;
   size_t pkgdatadirlen = strlen (pkgdatadir);
   while (pkgdatadirlen && pkgdatadir[pkgdatadirlen - 1] == '/')


@@ -492,62 +588,94 @@ output_skeleton (void)
   full_skeleton = xmalloc (pkgdatadirlen + 1
                           + (skeleton_size < sizeof m4sugar
                              ? sizeof m4sugar : skeleton_size));
   full_skeleton = xmalloc (pkgdatadirlen + 1
                           + (skeleton_size < sizeof m4sugar
                              ? sizeof m4sugar : skeleton_size));

-  strcpy (full_skeleton, pkgdatadir);
+  strncpy (full_skeleton, pkgdatadir, pkgdatadirlen);

   full_skeleton[pkgdatadirlen] = '/';
   strcpy (full_skeleton + pkgdatadirlen + 1, m4sugar);
   full_m4sugar = xstrdup (full_skeleton);
   strcpy (full_skeleton + pkgdatadirlen + 1, m4bison);
   full_m4bison = xstrdup (full_skeleton);
   full_skeleton[pkgdatadirlen] = '/';
   strcpy (full_skeleton + pkgdatadirlen + 1, m4sugar);
   full_m4sugar = xstrdup (full_skeleton);
   strcpy (full_skeleton + pkgdatadirlen + 1, m4bison);
   full_m4bison = xstrdup (full_skeleton);

-  strcpy (full_skeleton + pkgdatadirlen + 1, skeleton);
+  if (strchr (skeleton, '/'))
+    strcpy (full_skeleton, skeleton);
+  else
+    strcpy (full_skeleton + pkgdatadirlen + 1, skeleton);
+
+  /* Test whether m4sugar.m4 is readable, to check for proper
+     installation.  A faulty installation can cause deadlock, so a
+     cheap sanity check is worthwhile.  */

   xfclose (xfopen (full_m4sugar, "r"));
 
   /* Create an m4 subprocess connected to us via two pipes.  */
 
   if (trace_flag & trace_tools)
     fprintf (stderr, "running: %s %s - %s %s\n",
   xfclose (xfopen (full_m4sugar, "r"));
 
   /* Create an m4 subprocess connected to us via two pipes.  */
 
   if (trace_flag & trace_tools)
     fprintf (stderr, "running: %s %s - %s %s\n",

-            m4, full_m4sugar, full_m4bison, full_skeleton);
-
-  argv[0] = m4;
-  argv[1] = full_m4sugar;
-  argv[2] = "-";
-  argv[3] = full_m4bison;
-  argv[4] = full_skeleton;
-  argv[5] = trace_flag & trace_m4 ? "-dV" : NULL;
-  argv[6] = NULL;
-
-  init_subpipe ();
-  pid = create_subpipe (argv, filter_fd);
-  free (full_m4bison);
-  free (full_m4sugar);
-  free (full_skeleton);
+             m4, full_m4sugar, full_m4bison, full_skeleton);

 
 

-  out = fdopen (filter_fd[0], "w");
-  if (! out)
-    error (EXIT_FAILURE, get_errno (),
-          "fdopen");
+  /* Some future version of GNU M4 (most likely 1.6) may treat the -dV in a
+     position-dependent manner.  Keep it as the first argument so that all
+     files are traced.

 
 

-  /* Output the definitions of all the muscles.  */
-  fputs ("m4_init()\n", out);
+     See the thread starting at
+     <http://lists.gnu.org/archive/html/bug-bison/2008-07/msg00000.html>
+     for details.  */
+  {
+    int i = 0;
+    argv[i++] = m4;
+
+    /* When POSIXLY_CORRECT is set, GNU M4 1.6 and later disable GNU
+       extensions, which Bison's skeletons depend on.  With older M4,
+       it has no effect.  M4 1.4.12 added a -g/--gnu command-line
+       option to make it explicit that a program wants GNU M4
+       extensions even when POSIXLY_CORRECT is set.
+
+       See the thread starting at
+       <http://lists.gnu.org/archive/html/bug-bison/2008-07/msg00000.html>
+       for details.  */
+    if (*M4_GNU_OPTION)
+      argv[i++] = M4_GNU_OPTION;
+
+    argv[i++] = "-I";
+    argv[i++] = pkgdatadir;
+    if (trace_flag & trace_m4)
+      argv[i++] = "-dV";
+    argv[i++] = full_m4sugar;
+    argv[i++] = "-";
+    argv[i++] = full_m4bison;
+    argv[i++] = full_skeleton;
+    argv[i++] = NULL;
+    aver (i <= ARRAY_CARDINALITY (argv));
+  }

 
 

-  user_actions_output (out);
-  merger_output (out);
-  token_definitions_output (out);
-  symbol_code_props_output (out, "destructors", &symbol_destructor_get);
-  symbol_code_props_output (out, "printers", &symbol_printer_get);
+  /* The ugly cast is because gnulib gets the const-ness wrong.  */
+  pid = create_pipe_bidi ("m4", m4, (char **)(void*)argv, false, true,
+                          true, filter_fd);
+  free (full_m4sugar);
+  free (full_m4bison);
+  free (full_skeleton);

 
 

-  muscles_m4_output (out);
-  xfclose (out);
+  if (trace_flag & trace_muscles)
+    muscles_output (stderr);
+  {
+    FILE *out = fdopen (filter_fd[1], "w");
+    if (! out)
+      error (EXIT_FAILURE, get_errno (),
+             "fdopen");
+    muscles_output (out);
+    xfclose (out);
+  }

 
   /* Read and process m4's output.  */
   timevar_push (TV_M4);
 
   /* Read and process m4's output.  */
   timevar_push (TV_M4);

-  end_of_output_subpipe (pid, filter_fd);
-  in = fdopen (filter_fd[1], "r");
+  in = fdopen (filter_fd[0], "r");

   if (! in)
     error (EXIT_FAILURE, get_errno (),
           "fdopen");
   scan_skel (in);
   if (! in)
     error (EXIT_FAILURE, get_errno (),
           "fdopen");
   scan_skel (in);

+  /* scan_skel should have read all of M4's output.  Otherwise, when we
+     close the pipe, we risk letting M4 report a broken-pipe to the
+     Bison user.  */
+  aver (feof (in));

   xfclose (in);
   xfclose (in);

-  reap_subpipe (pid, m4);
+  wait_subprocess (pid, "m4", false, false, true, true, NULL);

   timevar_pop (TV_M4);
 }
 
   timevar_pop (TV_M4);
 }
 


@@ -564,15 +692,9 @@ prepare (void)
     use_push_for_pull_flag = true;
 
   /* Flags. */
     use_push_for_pull_flag = true;
 
   /* Flags. */

-  MUSCLE_INSERT_BOOL ("debug_flag", debug_flag);

   MUSCLE_INSERT_BOOL ("defines_flag", defines_flag);
   MUSCLE_INSERT_BOOL ("defines_flag", defines_flag);

-  MUSCLE_INSERT_BOOL ("error_verbose_flag", error_verbose);

   MUSCLE_INSERT_BOOL ("glr_flag", glr_parser);
   MUSCLE_INSERT_BOOL ("glr_flag", glr_parser);

-  MUSCLE_INSERT_BOOL ("locations_flag", locations_flag);

   MUSCLE_INSERT_BOOL ("nondeterministic_flag", nondeterministic_parser);
   MUSCLE_INSERT_BOOL ("nondeterministic_flag", nondeterministic_parser);

-  MUSCLE_INSERT_BOOL ("pull_flag", pull_parser);
-  MUSCLE_INSERT_BOOL ("pure_flag", pure_parser);
-  MUSCLE_INSERT_BOOL ("push_flag", push_parser);

   MUSCLE_INSERT_BOOL ("synclines_flag", !no_lines_flag);
   MUSCLE_INSERT_BOOL ("tag_seen_flag", tag_seen);
   MUSCLE_INSERT_BOOL ("use_push_for_pull_flag", use_push_for_pull_flag);
   MUSCLE_INSERT_BOOL ("synclines_flag", !no_lines_flag);
   MUSCLE_INSERT_BOOL ("tag_seen_flag", tag_seen);
   MUSCLE_INSERT_BOOL ("use_push_for_pull_flag", use_push_for_pull_flag);


@@ -603,12 +725,10 @@ prepare (void)
 
   /* About the skeletons.  */
   {
 
   /* About the skeletons.  */
   {

-    char const *pkgdatadir = getenv ("BISON_PKGDATADIR");

     /* b4_pkgdatadir is used inside m4_include in the skeletons, so digraphs
        would never be expanded.  Hopefully no one has M4-special characters in
        his Bison installation path.  */
     /* b4_pkgdatadir is used inside m4_include in the skeletons, so digraphs
        would never be expanded.  Hopefully no one has M4-special characters in
        his Bison installation path.  */

-    MUSCLE_INSERT_STRING_RAW ("pkgdatadir",
-                              pkgdatadir ? pkgdatadir : PKGDATADIR);
+    MUSCLE_INSERT_STRING_RAW ("pkgdatadir", compute_pkgdatadir ());

   }
 }
 
   }
 }
 


@@ -626,6 +746,7 @@ output (void)
   prepare_rules ();
   prepare_states ();
   prepare_actions ();
   prepare_rules ();
   prepare_states ();
   prepare_actions ();

+  prepare_symbol_definitions ();

 
   prepare ();
 
 
   prepare ();
 


@@ -634,3 +755,10 @@ output (void)
 
   obstack_free (&format_obstack, NULL);
 }
 
   obstack_free (&format_obstack, NULL);
 }

+
+char const *
+compute_pkgdatadir (void)
+{
+  char const *pkgdatadir = getenv ("BISON_PKGDATADIR");
+  return pkgdatadir ? pkgdatadir : PKGDATADIR;
+}