bison.simple

&#8226 一个词法分析器,他的功能是将字符流(例如源文件)转换为记号(例如关键词,操作符等等).

      if (yyssp >= yyss + yystacksize - 1)

	YYABORT;

    }



#if YYDEBUG != 0

  if (yydebug)

    fprintf(stderr, "Entering state %d\n", yystate);

#endif



  goto yybackup;

 yybackup:



/* Do appropriate processing given the current state.  */

/* Read a lookahead token if we need one and don't already have one.  */

/* yyresume: */



  /* First try to decide what to do without reference to lookahead token.  */



  yyn = yypact[yystate];

  if (yyn == YYFLAG)

    goto yydefault;



  /* Not known => get a lookahead token if don't already have one.  */



  /* yychar is either YYEMPTY or YYEOF

     or a valid token in external form.  */



  if (yychar == YYEMPTY)

    {

#if YYDEBUG != 0

      if (yydebug)

	fprintf(stderr, "Reading a token: ");

#endif

      yychar = YYLEX;

    }



  /* Convert token to internal form (in yychar1) for indexing tables with */



  if (yychar <= 0)		/* This means end of input. */

    {

      yychar1 = 0;

      yychar = YYEOF;		/* Don't call YYLEX any more */



#if YYDEBUG != 0

      if (yydebug)

	fprintf(stderr, "Now at end of input.\n");

#endif

    }

  else

    {

      yychar1 = YYTRANSLATE(yychar);



#if YYDEBUG != 0

      if (yydebug)

	{

	  fprintf (stderr, "Next token is %d (%s", yychar, yytname[yychar1]);

	  /* Give the individual parser a way to print the precise meaning

	     of a token, for further debugging info.  */

#ifdef YYPRINT

	  YYPRINT (stderr, yychar, yylval);

#endif

	  fprintf (stderr, ")\n");

	}

#endif

    }



  yyn += yychar1;

  if (yyn < 0 || yyn > YYLAST || yycheck[yyn] != yychar1)

    goto yydefault;



  yyn = yytable[yyn];



  /* yyn is what to do for this token type in this state.

     Negative => reduce, -yyn is rule number.

     Positive => shift, yyn is new state.

       New state is final state => don't bother to shift,

       just return success.

     0, or most negative number => error.  */



  if (yyn < 0)

    {

      if (yyn == YYFLAG)

	goto yyerrlab;

      yyn = -yyn;

      goto yyreduce;

    }

  else if (yyn == 0)

    goto yyerrlab;



  if (yyn == YYFINAL)

    YYACCEPT;



  /* Shift the lookahead token.  */



#if YYDEBUG != 0

  if (yydebug)

    fprintf(stderr, "Shifting token %d (%s), ", yychar, yytname[yychar1]);

#endif



  /* Discard the token being shifted unless it is eof.  */

  if (yychar != YYEOF)

    yychar = YYEMPTY;



  *++yyvsp = yylval;

#ifdef YYLSP_NEEDED

  *++yylsp = yylloc;

#endif



  /* count tokens shifted since error; after three, turn off error status.  */

  if (yyerrstatus) yyerrstatus--;



  yystate = yyn;

  goto yynewstate;



/* Do the default action for the current state.  */

yydefault:



  yyn = yydefact[yystate];

  if (yyn == 0)

    goto yyerrlab;



/* Do a reduction.  yyn is the number of a rule to reduce with.  */

yyreduce:

  yylen = yyr2[yyn];

  if (yylen > 0)

    yyval = yyvsp[1-yylen]; /* implement default value of the action */



#if YYDEBUG != 0

  if (yydebug)

    {

      int i;



      fprintf (stderr, "Reducing via rule %d (line %d), ",

	       yyn, yyrline[yyn]);



      /* Print the symbols being reduced, and their result.  */

      for (i = yyprhs[yyn]; yyrhs[i] > 0; i++)

	fprintf (stderr, "%s ", yytname[yyrhs[i]]);

      fprintf (stderr, " -> %s\n", yytname[yyr1[yyn]]);

    }

#endif



$   /* the action file gets copied in in place of this dollarsign */

#line 487 "bison.simple"



  yyvsp -= yylen;

  yyssp -= yylen;

#ifdef YYLSP_NEEDED

  yylsp -= yylen;

#endif



#if YYDEBUG != 0

  if (yydebug)

    {

      short *ssp1 = yyss - 1;

      fprintf (stderr, "state stack now");

      while (ssp1 != yyssp)

	fprintf (stderr, " %d", *++ssp1);

      fprintf (stderr, "\n");

    }

#endif



  *++yyvsp = yyval;



#ifdef YYLSP_NEEDED

  yylsp++;

  if (yylen == 0)

    {

      yylsp->first_line = yylloc.first_line;

      yylsp->first_column = yylloc.first_column;

      yylsp->last_line = (yylsp-1)->last_line;

      yylsp->last_column = (yylsp-1)->last_column;

      yylsp->text = 0;

    }

  else

    {

      yylsp->last_line = (yylsp+yylen-1)->last_line;

      yylsp->last_column = (yylsp+yylen-1)->last_column;

    }

#endif



  /* Now "shift" the result of the reduction.

     Determine what state that goes to,

     based on the state we popped back to

     and the rule number reduced by.  */



  yyn = yyr1[yyn];



  yystate = yypgoto[yyn - YYNTBASE] + *yyssp;

  if (yystate >= 0 && yystate <= YYLAST && yycheck[yystate] == *yyssp)

    yystate = yytable[yystate];

  else

    yystate = yydefgoto[yyn - YYNTBASE];



  goto yynewstate;



yyerrlab:   /* here on detecting error */



  if (! yyerrstatus)

    /* If not already recovering from an error, report this error.  */

    {

      ++yynerrs;



#ifdef YYERROR_VERBOSE

      yyn = yypact[yystate];



      if (yyn > YYFLAG && yyn < YYLAST)

	{

	  int size = 0;

	  char *msg;

	  int x, count;



	  count = 0;

	  /* Start X at -yyn if nec to avoid negative indexes in yycheck.  */

	  for (x = (yyn < 0 ? -yyn : 0);

	       x < (sizeof(yytname) / sizeof(char *)); x++)

	    if (yycheck[x + yyn] == x)

	      size += strlen(yytname[x]) + 15, count++;

	  msg = (char *) malloc(size + 15);

	  if (msg != 0)

	    {

	      strcpy(msg, "parse error");



	      if (count < 5)

		{

		  count = 0;

		  for (x = (yyn < 0 ? -yyn : 0);

		       x < (sizeof(yytname) / sizeof(char *)); x++)

		    if (yycheck[x + yyn] == x)

		      {

			strcat(msg, count == 0 ? ", expecting `" : " or `");

			strcat(msg, yytname[x]);

			strcat(msg, "'");

			count++;

		      }

		}

	      yyerror(msg);

	      free(msg);

	    }

	  else

	    yyerror ("parse error; also virtual memory exceeded");

	}

      else

#endif /* YYERROR_VERBOSE */

	yyerror("parse error");

    }



  goto yyerrlab1;

yyerrlab1:   /* here on error raised explicitly by an action */



  if (yyerrstatus == 3)

    {

      /* if just tried and failed to reuse lookahead token after an error, discard it.  */



      /* return failure if at end of input */

      if (yychar == YYEOF)

	YYABORT;



#if YYDEBUG != 0

      if (yydebug)

	fprintf(stderr, "Discarding token %d (%s).\n", yychar, yytname[yychar1]);

#endif



      yychar = YYEMPTY;

    }



  /* Else will try to reuse lookahead token

     after shifting the error token.  */



  yyerrstatus = 3;		/* Each real token shifted decrements this */



  goto yyerrhandle;



yyerrdefault:  /* current state does not do anything special for the error token. */



#if 0

  /* This is wrong; only states that explicitly want error tokens

     should shift them.  */

  yyn = yydefact[yystate];  /* If its default is to accept any token, ok.  Otherwise pop it.*/

  if (yyn) goto yydefault;

#endif



yyerrpop:   /* pop the current state because it cannot handle the error token */



  if (yyssp == yyss) YYABORT;

  yyvsp--;

  yystate = *--yyssp;

#ifdef YYLSP_NEEDED

  yylsp--;

#endif



#if YYDEBUG != 0

  if (yydebug)

    {

      short *ssp1 = yyss - 1;

      fprintf (stderr, "Error: state stack now");

      while (ssp1 != yyssp)

	fprintf (stderr, " %d", *++ssp1);

      fprintf (stderr, "\n");

    }

#endif



yyerrhandle:



  yyn = yypact[yystate];

  if (yyn == YYFLAG)

    goto yyerrdefault;



  yyn += YYTERROR;

  if (yyn < 0 || yyn > YYLAST || yycheck[yyn] != YYTERROR)

    goto yyerrdefault;



  yyn = yytable[yyn];

  if (yyn < 0)

    {

      if (yyn == YYFLAG)

	goto yyerrpop;

      yyn = -yyn;

      goto yyreduce;

    }

  else if (yyn == 0)

    goto yyerrpop;



  if (yyn == YYFINAL)

    YYACCEPT;



#if YYDEBUG != 0

  if (yydebug)

    fprintf(stderr, "Shifting error token, ");

#endif



  *++yyvsp = yylval;

#ifdef YYLSP_NEEDED

  *++yylsp = yylloc;

#endif



  yystate = yyn;

  goto yynewstate;

}