compile.c

/* Copyright (c) 2007 by Ian Piumarta
 * All rights reserved.
 * 
 * Permission is hereby granted, free of charge, to any person obtaining a
 * copy of this software and associated documentation files (the 'Software'),
 * to deal in the Software without restriction, including without limitation
 * the rights to use, copy, modify, merge, publish, distribute, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, provided that the above copyright notice(s) and this
 * permission notice appear in all copies of the Software.  Acknowledgement
 * of the use of this Software in supporting documentation would be
 * appreciated but is not required.
 * 
 * THE SOFTWARE IS PROVIDED 'AS IS'.  USE ENTIRELY AT YOUR OWN RISK.
 * 
 * Last edited: 2007-08-31 13:55:23 by piumarta on emilia.local
 */

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <assert.h>

#include "greg.h"

static int yyl(void)
{
  static int prev= 0;
  return ++prev;
}

static void charClassSet  (unsigned char bits[], int c) { bits[c >> 3] |=  (1 << (c & 7)); }
static void charClassClear(unsigned char bits[], int c) { bits[c >> 3] &= ~(1 << (c & 7)); }

typedef void (*setter)(unsigned char bits[], int c);

static int readChar(unsigned char **cp)
{
  unsigned char *cclass = *cp;
  int c= *cclass++, i = 0;
  if ('\\' == c && *cclass)
        {
    c= *cclass++;
    if (c >= '0' && c <= '9')
      {
        unsigned char oct= 0;
        for (i= 2; i >= 0; i--) {
          if (!(c >= '0' && c <= '9'))
            break;
          oct= (oct * 8) + (c - '0');
          c= *cclass++;
        }
        cclass--;
        c= oct;
        goto done;
      }

    switch (c)
      {
      case 'a':  c= '\a'; break;        /* bel */
      case 'b':  c= '\b'; break;        /* bs */
      case 'e':  c= '\e'; break;        /* esc */
      case 'f':  c= '\f'; break;        /* ff */
      case 'n':  c= '\n'; break;        /* nl */
      case 'r':  c= '\r'; break;        /* cr */
      case 't':  c= '\t'; break;        /* ht */
      case 'v':  c= '\v'; break;        /* vt */
      default:          break;
      }
        }

done:
  *cp = cclass;
  return c;
}

static char *makeCharClass(unsigned char *cclass)
{
  unsigned char  bits[32];
  setter         set;
  int            c, prev= -1;
  static char    string[256];
  char          *ptr;

  if ('^' == *cclass)
    {
      memset(bits, 255, 32);
      set= charClassClear;
      ++cclass;
    }
  else
    {
      memset(bits, 0, 32);
      set= charClassSet;
    }
  while (0 != (c= readChar(&cclass)))
    {
      if ('-' == c && *cclass && prev >= 0)
        {
          for (c= readChar(&cclass); prev <= c; ++prev)
            set(bits, prev);
          prev= -1;
        }
      else
  {
    set(bits, prev= c);
  }
    }

  ptr= string;
  for (c= 0;  c < 32;  ++c)
    ptr += sprintf(ptr, "\\%03o", bits[c]);

  return string;
}

static void begin(void)         { fprintf(output, "\n  {"); }
static void end(void)           { fprintf(output, "\n  }"); }
static void label(int n)        { fprintf(output, "\n  l%d:;\t", n); }
static void jump(int n)         { fprintf(output, "  goto l%d;", n); }
static void jumperror(int n)    { fprintf(output, "  if (G->error.msg) goto l%d;", n); }
static void save(int n)         { fprintf(output, "  yystate state%d= G->state;\n", n); }
static void errorstore(int n)   { fprintf(output, "  const char* error%d= 0; error%d=error%d;\n", n, n, n); }
static void restore(int n)      { fprintf(output, "  G->state = state%d;", n); }

static void callErrBlock(Node * node) {
    fprintf(output, " { YY_XTYPE YY_XVAR = (YY_XTYPE) G->data; int yyindex = G->offset + G->state.pos; %s; }", ((struct Any*) node)->errblock);
}

static void Node_compile_c_ko(Node *node, int ko, int depth)
{
  assert(node);
  switch (node->type)
    {
    case Rule:
      fprintf(stderr, "\ninternal error #1 (%s)\n", node->rule.name);
      exit(1);
      break;

    case Dot:
      fprintf(output, "  if (!yymatchDot(G)) goto l%d;", ko);
      break;

    case Name:
      {
        fprintf(output, "  if (!yy_%s(G)) {", node->name.rule->rule.name);
        if(((struct Any*) node)->errblock) {
            callErrBlock(node);
        }
        fprintf(output, " if (error%d) { yyseterror(&G->error, &G->state, error%d); return 0; }", depth, depth);
        fprintf(output, " goto l%d; }", ko);
        if (node->name.variable)
          fprintf(output, "  yyDo(G, yySet, %d, 0);", node->name.variable->variable.offset);
      }
      break;

    case Character:
    case String:
      {
        int len= strlen(node->string.value);
        if (1 == len || (2 == len && '\\' == node->string.value[0]))
          fprintf(output, "  if (!yymatchChar(G, '%s')) goto l%d;", node->string.value, ko);
        else
          fprintf(output, "  if (!yymatchString(G, \"%s\")) goto l%d;", node->string.value, ko);
      }
      break;

    case Class:
      fprintf(output, "  if (!yymatchClass(G, (unsigned char *)\"%s\")) goto l%d;", makeCharClass(node->cclass.value), ko);
      break;

    case Action:
      fprintf(output, "  yyDo(G, yy%s, textpos?textpos:G->state.textpos, G->end);", node->action.name);
      break;

    case Predicate:
      fprintf(output, "  yyText(G, textpos?textpos:G->state.textpos, G->end);  if (!(%s)) goto l%d;", node->action.text, ko);
      break;

    case NoBack:
      fprintf(output, "  error%d = \"%s\";\n", depth, node->noback.msg);
      break;

    case Alternate:
      {
        int ok= yyl();
        begin();
        save(ok);
        errorstore(depth+1);
        for (node= node->alternate.first;  node;  node= node->alternate.next)
          if (node->alternate.next)
            {
              int next= yyl();
              Node_compile_c_ko(node, next, depth+1);
              jump(ok);
              label(next);
              jumperror(ok);
              restore(ok);
            }
          else
            Node_compile_c_ko(node, ko, depth+1);
        end();
        label(ok);
      }
      break;

    case Sequence:
      begin();
      errorstore(depth+1);
      for (node= node->sequence.first;  node;  node= node->sequence.next)
        Node_compile_c_ko(node, ko, depth+1);
      end();
      break;

    case PeekFor:
      {
        int ok= yyl();
        begin();
        save(ok);
        errorstore(depth+1);
        Node_compile_c_ko(node->peekFor.element, ko, depth+1);
        restore(ok);
        end();
      }
      break;

    case PeekNot:
      {
        int ok= yyl();
        begin();
        save(ok);
        errorstore(depth+1);
        Node_compile_c_ko(node->peekFor.element, ok, depth+1);
        jump(ko);
        label(ok);
        restore(ok);
        end();
      }
      break;

    case Query:
      {
        int qko= yyl(), qok= yyl();
        begin();
        save(qko);
        errorstore(depth+1);
        Node_compile_c_ko(node->query.element, qko, depth+1);
        jump(qok);
        label(qko);
        restore(qko);
        end();
        label(qok);
      }
      break;

    case Star:
      {
        int again= yyl(), out= yyl();
        label(again);
        begin();
        save(out);
        errorstore(depth+1);
        Node_compile_c_ko(node->star.element, out, depth+1);
        jumperror(out);
        jump(again);
        label(out);
        restore(out);
        end();
      }
      break;

    case Plus:
      {
        int again= yyl(), out= yyl();
        begin();
        errorstore(depth+1);
        Node_compile_c_ko(node->plus.element, ko, depth+1);
        label(again);
        save(out);
        Node_compile_c_ko(node->plus.element, out, depth+1);
        jumperror(out);
        jump(again);
        label(out);
        restore(out);
        end();
      }
      break;

    default:
      fprintf(stderr, "\nNode_compile_c_ko: illegal node type %d\n", node->type);
      exit(1);
    }
}


static int countVariables(Node *node)
{
  int count= 0;
  while (node)
    {
      ++count;
      node= node->variable.next;
    }
  return count;
}

static void defineVariables(Node *node)
{
  int count= 0;
  while (node)
    {
      fprintf(output, "#define %s G->val[%d]\n", node->variable.name, --count);
      node->variable.offset= count;
      node= node->variable.next;
    }
}

static void undefineVariables(Node *node)
{
  while (node)
    {
      fprintf(output, "#undef %s\n", node->variable.name);
      node= node->variable.next;
    }
}


static void Rule_compile_c2(Node *node)
{
  assert(node);
  assert(Rule == node->type);

  if (!node->rule.expression)
    fprintf(stderr, "rule '%s' used but not defined\n", node->rule.name);
  else
    {
      int ko= yyl(), safe;

      if ((!(RuleUsed & node->rule.flags)) && (node != start))
        fprintf(stderr, "rule '%s' defined but not used\n", node->rule.name);

      safe= ((Query == node->rule.expression->type) || (Star == node->rule.expression->type));

      fprintf(output, "\nYY_RULE(int) yy_%s(GREG *G)\n{\n", node->rule.name);
      fprintf(output, "  int textpos= 0; textpos=textpos;\n");
      if (!safe) save(0);
      if (node->rule.variables)
        fprintf(output, "  yyDo(G, yyPush, %d, 0);", countVariables(node->rule.variables));
      fprintf(output, "\n  yyprintf((stderr, \"%%s\\n\", \"%s\"));", node->rule.name);
      errorstore(0);
      Node_compile_c_ko(node->rule.expression, ko, 0);
      fprintf(output, "\n  yyprintf((stderr, \"  ok   %%s @ %%s\\n\", \"%s\", G->buf+G->state.pos));", node->rule.name);
      if (node->rule.variables)
        fprintf(output, "  yyDo(G, yyPop, %d, 0);", countVariables(node->rule.variables));
      fprintf(output, "\n  if (G->error.msg) return 0;\n");
      // done for backwards compatiblity, where we scoop up text from other rules ... globally
      fprintf(output, "\n  if (textpos) G->state.textpos = textpos;\n");
      fprintf(output, "\n  return 1;");
      if (!safe)
        {
          label(ko);
          restore(0);
          fprintf(output, "\n  yyprintf((stderr, \"  fail %%s @ %%s\\n\", \"%s\", G->buf+G->state.pos));", node->rule.name);
          fprintf(output, "\n  return 0;");
        }
      fprintf(output, "\n}");
    }

  if (node->rule.next)
    Rule_compile_c2(node->rule.next);
}

static char *header= "\
#include <stdio.h>\n\
#include <stdlib.h>\n\
#include <string.h>\n\
struct _GREG;\n\
";

static char *preamble= "\
#ifndef YY_ALLOC\n\
#define YY_ALLOC(N, D) malloc(N)\n\
#endif\n\
#ifndef YY_CALLOC\n\
#define YY_CALLOC(N, S, D) calloc(N, S)\n\
#endif\n\
#ifndef YY_REALLOC\n\
#define YY_REALLOC(B, N, D) realloc(B, N)\n\
#endif\n\
#ifndef YY_FREE\n\
#define YY_FREE free\n\
#endif\n\
#ifndef YY_LOCAL\n\
#define YY_LOCAL(T)     static T\n\
#endif\n\
#ifndef YY_ACTION\n\
#define YY_ACTION(T)    static T\n\
#endif\n\
#ifndef YY_RULE\n\
#define YY_RULE(T)      static T\n\
#endif\n\
#ifndef YY_PARSE\n\
#define YY_PARSE(T)     T\n\
#endif\n\
#ifndef YY_NAME\n\
#define YY_NAME(N) yy##N\n\
#endif\n\
#ifndef YY_INPUT\n\
#define YY_INPUT(buf, result, max_size, D)              \\\n\
  {                                                     \\\n\
    int yyc= getchar();                                 \\\n\
    result= (EOF == yyc) ? 0 : (*(buf)= yyc, 1);        \\\n\
    yyprintf((stderr, \"<%c>\", yyc));                  \\\n\
  }\n\
#endif\n\
#ifndef YY_BEGIN\n\
#define YY_BEGIN        ( textpos= G->state.textpos= G->state.pos, 1)\n\
#endif\n\
#ifndef YY_END\n\
#define YY_END          ( G->end= G->state.pos, 1)\n\
#endif\n\
#ifdef YY_DEBUG\n\
# define yyprintf(args) fprintf args\n\
#else\n\
# define yyprintf(args)\n\
#endif\n\
#ifndef YYSTYPE\n\
#define YYSTYPE int\n\
#endif\n\
#ifndef YY_XTYPE\n\
#define YY_XTYPE void *\n\
#endif\n\
#ifndef YY_XVAR\n\
#define YY_XVAR yyxvar\n\
#endif\n\
\n\
#ifndef YY_STACK_SIZE\n\
#define YY_STACK_SIZE 128\n\
#endif\n\
\n\
#ifndef YY_BUFFER_START_SIZE\n\
#define YY_BUFFER_START_SIZE 1024\n\
#endif\n\
\n\
#ifndef YY_PART\n\
#define yydata G->data\n\
#define yy G->ss\n\
\n\
typedef struct _yystate {\n\
    int textpos;\n\
    int line;\n\
    int pos;\n\
    int thunkpos;\n\
} yystate;\n\
\n\
typedef struct _yyerror {\n\
    const char* msg;\n\
    int line;\n\
    int pos;\n\
} yyerror;\n\
\n\
struct _yythunk; // forward declaration\n\
typedef void (*yyaction)(struct _GREG *G, char *yytext, int yyleng, struct _yythunk *thunkpos, YY_XTYPE YY_XVAR);\n\
typedef struct _yythunk { int begin, end;  yyaction  action;  struct _yythunk *next; } yythunk;\n\
\n\
typedef struct _GREG {\n\
  yystate state;\n\
  yyerror error;\n\
  char *buf;\n\
  int buflen;\n\
  int   offset;\n\
  int   limit;\n\
  char *text;\n\
  int   textlen;\n\
  int   end;\n\
  yythunk *thunks;\n\
  int   thunkslen;\n\
  YYSTYPE ss;\n\
  YYSTYPE *val;\n\
  YYSTYPE *vals;\n\
  int valslen;\n\
  YY_XTYPE data;\n\
} GREG;\n\
\n\
YY_LOCAL(void) yyseterror(yyerror *error, yystate *state, const char* msg) {\n\
    if (error->msg) return;\n\
    error->msg = msg;\n\
    error->line = state->line;\n\
    error->pos = state->pos;\n\
}\n\
\n\
YY_LOCAL(int) yyrefill(GREG *G)\n\
{\n\
  int yyn;\n\
  while (G->buflen - G->state.pos < 512)\n\
    {\n\
      G->buflen *= 2;\n\
      G->buf= (char*)YY_REALLOC(G->buf, G->buflen, G->data);\n\
    }\n\
  YY_INPUT((G->buf + G->state.pos), yyn, (G->buflen - G->state.pos), G->data);\n\
  if (!yyn) return 0;\n\
  G->limit += yyn;\n\
  return 1;\n\
}\n\
\n\
YY_LOCAL(int) yymatchDot(GREG *G)\n\
{\n\
  if (G->state.pos >= G->limit && !yyrefill(G)) return 0;\n\
  if (G->buf[G->state.pos] == '\\n') G->state.line++;\n\
  G->state.pos++;\n\
  return 1;\n\
}\n\
\n\
YY_LOCAL(int) yymatchChar(GREG *G, int c)\n\
{\n\
  if (G->state.pos >= G->limit && !yyrefill(G)) return 0;\n\
  if ((unsigned char)G->buf[G->state.pos] == c)\n\
    {\n\
      if (G->buf[G->state.pos] == '\\n') G->state.line++;\n\
      G->state.pos++;\n\
      yyprintf((stderr, \"  ok   yymatchChar(%c) @ %s\\n\", c, G->buf+G->state.pos));\n\
      return 1;\n\
    }\n\
  yyprintf((stderr, \"  fail yymatchChar(%c) @ %s\\n\", c, G->buf+G->state.pos));\n\
  return 0;\n\
}\n\
\n\
YY_LOCAL(int) yymatchString(GREG *G, const char *s)\n\
{\n\
  yystate state = G->state;\n\
  while (*s)\n\
    {\n\
      if (G->state.pos >= G->limit && !yyrefill(G)) return 0;\n\
      if (G->buf[G->state.pos] != *s)\n\
        {\n\
          G->state = state;\n\
          return 0;\n\
        }\n\
      if (G->buf[G->state.pos] == '\\n') G->state.line++;\n\
      s++;\n\
      G->state.pos++;\n\
    }\n\
  return 1;\n\
}\n\
\n\
YY_LOCAL(int) yymatchClass(GREG *G, unsigned char *bits)\n\
{\n\
  int c;\n\
  if (G->state.pos >= G->limit && !yyrefill(G)) return 0;\n\
  c= (unsigned char)G->buf[G->state.pos];\n\
  if (bits[c >> 3] & (1 << (c & 7)))\n\
    {\n\
      if (G->buf[G->state.pos] == '\\n') G->state.line++;\n\
      G->state.pos++;\n\
      yyprintf((stderr, \"  ok   yymatchClass @ %s\\n\", G->buf+G->state.pos));\n\
      return 1;\n\
    }\n\
  yyprintf((stderr, \"  fail yymatchClass @ %s\\n\", G->buf+G->state.pos));\n\
  return 0;\n\
}\n\
\n\
YY_LOCAL(void) yyDo(GREG *G, yyaction action, int begin, int end)\n\
{\n\
  while (G->state.thunkpos >= G->thunkslen)\n\
    {\n\
      G->thunkslen *= 2;\n\
      G->thunks= (yythunk*)YY_REALLOC(G->thunks, sizeof(yythunk) * G->thunkslen, G->data);\n\
    }\n\
  G->thunks[G->state.thunkpos].begin=  begin;\n\
  G->thunks[G->state.thunkpos].end=    end;\n\
  G->thunks[G->state.thunkpos].action= action;\n\
  ++G->state.thunkpos;\n\
}\n\
\n\
YY_LOCAL(int) yyText(GREG *G, int begin, int end)\n\
{\n\
  int yyleng= end - begin;\n\
  if (yyleng <= 0)\n\
    yyleng= 0;\n\
  else\n\
    {\n\
      while (G->textlen < (yyleng - 1))\n\
        {\n\
          G->textlen *= 2;\n\
          G->text= (char*)YY_REALLOC(G->text, G->textlen, G->data);\n\
        }\n\
      memcpy(G->text, G->buf + begin, yyleng);\n\
    }\n\
  G->text[yyleng]= '\\0';\n\
  return yyleng;\n\
}\n\
\n\
YY_LOCAL(void) yyDone(GREG *G)\n\
{\n\
  int pos;\n\
  for (pos= 0; pos < G->state.thunkpos; ++pos)\n\
    {\n\
      yythunk *thunk= &G->thunks[pos];\n\
      int yyleng= thunk->end ? yyText(G, thunk->begin, thunk->end) : thunk->begin;\n\
      yyprintf((stderr, \"DO [%d] %p %s\\n\", pos, thunk->action, G->text));\n\
      thunk->action(G, G->text, yyleng, thunk, G->data);\n\
    }\n\
  G->state.thunkpos= 0;\n\
}\n\
\n\
YY_LOCAL(void) yyCommit(GREG *G)\n\
{\n\
  if ((G->limit -= G->state.pos))\n\
    {\n\
      memmove(G->buf, G->buf + G->state.pos, G->limit);\n\
    }\n\
  G->offset += G->state.pos;\n\
  G->state.textpos -= G->state.pos;\n\
  G->end -= G->state.pos;\n\
  G->state.pos= G->state.thunkpos= 0;\n\
}\n\
\n\
YY_LOCAL(int) yyAccept(GREG *G, int tp0)\n\
{\n\
  if (tp0)\n\
    {\n\
      fprintf(stderr, \"accept denied at %d\\n\", tp0);\n\
      return 0;\n\
    }\n\
  else\n\
    {\n\
      yyDone(G);\n\
      yyCommit(G);\n\
    }\n\
  return 1;\n\
}\n\
\n\
YY_LOCAL(void) yyPush(GREG *G, char *text, int count, yythunk *thunk, YY_XTYPE YY_XVAR) { G->val += count; }\n\
YY_LOCAL(void) yyPop(GREG *G, char *text, int count, yythunk *thunk, YY_XTYPE YY_XVAR)  { G->val -= count; }\n\
YY_LOCAL(void) yySet(GREG *G, char *text, int count, yythunk *thunk, YY_XTYPE YY_XVAR)  { G->val[count]= G->ss; }\n\
\n\
#endif /* YY_PART */\n\
\n\
#define YYACCEPT        yyAccept(G, yythunkpos0)\n\
\n\
";

static char *footer= "\n\
\n\
#ifndef YY_PART\n\
\n\
typedef int (*yyrule)(GREG *G);\n\
\n\
YY_PARSE(int) YY_NAME(parse_from)(GREG *G, yyrule yystart)\n\
{\n\
  int yyok;\n\
  if (!G->buflen)\n\
    {\n\
      G->buflen= YY_BUFFER_START_SIZE;\n\
      G->buf= (char*)YY_ALLOC(G->buflen, G->data);\n\
      G->textlen= YY_BUFFER_START_SIZE;\n\
      G->text= (char*)YY_ALLOC(G->textlen, G->data);\n\
      G->thunkslen= YY_STACK_SIZE;\n\
      G->thunks= (yythunk*)YY_ALLOC(sizeof(yythunk) * G->thunkslen, G->data);\n\
      G->valslen= YY_STACK_SIZE;\n\
      G->vals= (YYSTYPE*)YY_ALLOC(sizeof(YYSTYPE) * G->valslen, G->data);\n\
      G->limit = 0;\n\
    }\n\
  memset(&G->state, 0, sizeof(G->state)); G->state.line= 1;\n\
  memset(&G->error, 0, sizeof(G->error));\n\
  G->end= 0;\n\
  G->val= G->vals;\n\
  yyok= yystart(G);\n\
  if (yyok) {\n\
      yyDone(G);\n\
      yyCommit(G);\n\
  }\n\
  return yyok;\n\
  (void)yyrefill;\n\
  (void)yymatchDot;\n\
  (void)yymatchChar;\n\
  (void)yymatchString;\n\
  (void)yymatchClass;\n\
  (void)yyDo;\n\
  (void)yyText;\n\
  (void)yyDone;\n\
  (void)yyCommit;\n\
  (void)yyAccept;\n\
  (void)yyPush;\n\
  (void)yyPop;\n\
  (void)yySet;\n\
}\n\
\n\
YY_PARSE(int) YY_NAME(parse)(GREG *G)\n\
{\n\
  return YY_NAME(parse_from)(G, yy_%s);\n\
}\n\
\n\
YY_PARSE(void) YY_NAME(init)(GREG *G)\n\
{\n\
    memset(G, 0, sizeof(GREG));\n\
}\n\
YY_PARSE(void) YY_NAME(deinit)(GREG *G)\n\
{\n\
    if (G->buf) YY_FREE(G->buf);\n\
    if (G->text) YY_FREE(G->text);\n\
    if (G->thunks) YY_FREE(G->thunks);\n\
    if (G->vals) YY_FREE(G->vals);\n\
}\n\
YY_PARSE(GREG *) YY_NAME(parse_new)(YY_XTYPE data)\n\
{\n\
  GREG *G = (GREG *)YY_CALLOC(1, sizeof(GREG), G->data);\n\
  G->data = data;\n\
  return G;\n\
}\n\
\n\
YY_PARSE(void) YY_NAME(parse_free)(GREG *G)\n\
{\n\
  YY_NAME(deinit)(G);\n\
  YY_FREE(G);\n\
}\n\
\n\
#endif\n\
";

void Rule_compile_c_header(void)
{
  fprintf(output, "/* A recursive-descent parser generated by greg %d.%d.%d */\n", GREG_MAJOR, GREG_MINOR, GREG_LEVEL);
  fprintf(output, "\n");
  fprintf(output, "%s", header);
  fprintf(output, "#define YYRULECOUNT %d\n", ruleCount);
}

int consumesInput(Node *node)
{
  if (!node) return 0;

  switch (node->type)
    {
    case Rule:
      {
        int result= 0;
        if (RuleReached & node->rule.flags)
          fprintf(stderr, "possible infinite left recursion in rule '%s'\n", node->rule.name);
        else
          {
            node->rule.flags |= RuleReached;
            result= consumesInput(node->rule.expression);
            node->rule.flags &= ~RuleReached;
          }
        return result;
      }
      break;

    case Dot:           return 1;
    case Name:          return consumesInput(node->name.rule);
    case Character:
    case String:        return strlen(node->string.value) > 0;
    case Class:         return 1;
    case Action:        return 0;
    case Predicate:     return 0;
    case NoBack:        return 0;

    case Alternate:
      {
        Node *n;
        for (n= node->alternate.first;  n;  n= n->alternate.next)
          if (!consumesInput(n))
            return 0;
      }
      return 1;

    case Sequence:
      {
        Node *n;
        for (n= node->alternate.first;  n;  n= n->alternate.next)
          if (consumesInput(n))
            return 1;
      }
      return 0;

    case PeekFor:       return 0;
    case PeekNot:       return 0;
    case Query:         return 0;
    case Star:          return 0;
    case Plus:          return consumesInput(node->plus.element);

    default:
      fprintf(stderr, "\nconsumesInput: illegal node type %d\n", node->type);
      exit(1);
    }
  return 0;
}


void Rule_compile_c(Node *node)
{
  Node *n;

  for (n= rules;  n;  n= n->rule.next)
    consumesInput(n);

  fprintf(output, "%s", preamble);
  for (n= node;  n;  n= n->rule.next)
    fprintf(output, "YY_RULE(int) yy_%s(GREG *G); /* %d */\n", n->rule.name, n->rule.id);
  fprintf(output, "\n");
  for (n= actions;  n;  n= n->action.list)
    {
      fprintf(output, "YY_ACTION(void) yy%s(GREG *G, char *yytext, int yyleng, yythunk *thunk, YY_XTYPE YY_XVAR)\n{\n", n->action.name);
      defineVariables(n->action.rule->rule.variables);
      fprintf(output, "  yyprintf((stderr, \"do yy%s\\n\"));\n", n->action.name);
      fprintf(output, "  %s;\n", n->action.text);
      undefineVariables(n->action.rule->rule.variables);
      fprintf(output, "}\n");
    }
  Rule_compile_c2(node);
  fprintf(output, footer, start->rule.name);
}