yacc.c

bison 2.0 主要可以用来做语法分析用的

		    &yyvs1, yysize * sizeof (*yyvsp),
]b4_location_if([		    &yyls1, yysize * sizeof (*yylsp),])[
		    &yystacksize);
]b4_location_if([	yyls = yyls1;])[
	yyss = yyss1;
	yyvs = yyvs1;
      }
#else /* no yyoverflow */
# ifndef YYSTACK_RELOCATE
      goto yyoverflowlab;
# else
      /* Extend the stack our own way.  */
      if (YYMAXDEPTH <= yystacksize)
	goto yyoverflowlab;
      yystacksize *= 2;
      if (YYMAXDEPTH < yystacksize)
	yystacksize = YYMAXDEPTH;

      {
	short int *yyss1 = yyss;
	union yyalloc *yyptr =
	  (union yyalloc *) YYSTACK_ALLOC (YYSTACK_BYTES (yystacksize));
	if (! yyptr)
	  goto yyoverflowlab;
	YYSTACK_RELOCATE (yyss);
	YYSTACK_RELOCATE (yyvs);
]b4_location_if([	YYSTACK_RELOCATE (yyls);])[
#  undef YYSTACK_RELOCATE
	if (yyss1 != yyssa)
	  YYSTACK_FREE (yyss1);
      }
# endif
#endif /* no yyoverflow */

      yyssp = yyss + yysize - 1;
      yyvsp = yyvs + yysize - 1;
]b4_location_if([      yylsp = yyls + yysize - 1;])[

      YYDPRINTF ((stderr, "Stack size increased to %lu\n",
		  (unsigned long int) yystacksize));

      if (yyss + yystacksize - 1 <= yyssp)
	YYABORT;
    }

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

  goto yybackup;

/*-----------.
| yybackup.  |
`-----------*/
yybackup:

/* Do appropriate processing given the current state.  */
/* Read a look-ahead token if we need one and don't already have one.  */
/* yyresume: */

  /* First try to decide what to do without reference to look-ahead token.  */

  yyn = yypact[yystate];
  if (yyn == YYPACT_NINF)
    goto yydefault;

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

  /* YYCHAR is either YYEMPTY or YYEOF or a valid look-ahead symbol.  */
  if (yychar == YYEMPTY)
    {
      YYDPRINTF ((stderr, "Reading a token: "));
      yychar = YYLEX;
    }

  if (yychar <= YYEOF)
    {
      yychar = yytoken = YYEOF;
      YYDPRINTF ((stderr, "Now at end of input.\n"));
    }
  else
    {
      yytoken = YYTRANSLATE (yychar);
      YY_SYMBOL_PRINT ("Next token is", yytoken, &yylval, &yylloc);
    }

  /* If the proper action on seeing token YYTOKEN is to reduce or to
     detect an error, take that action.  */
  yyn += yytoken;
  if (yyn < 0 || YYLAST < yyn || yycheck[yyn] != yytoken)
    goto yydefault;
  yyn = yytable[yyn];
  if (yyn <= 0)
    {
      if (yyn == 0 || yyn == YYTABLE_NINF)
	goto yyerrlab;
      yyn = -yyn;
      goto yyreduce;
    }

  if (yyn == YYFINAL)
    YYACCEPT;

  /* Shift the look-ahead token.  */
  YY_SYMBOL_PRINT ("Shifting", yytoken, &yylval, &yylloc);

  /* Discard the token being shifted unless it is eof.  */
  if (yychar != YYEOF)
    yychar = YYEMPTY;

  *++yyvsp = yylval;
]b4_location_if([  *++yylsp = yylloc;])[

  /* Count tokens shifted since error; after three, turn off error
     status.  */
  if (yyerrstatus)
    yyerrstatus--;

  yystate = yyn;
  goto yynewstate;


/*-----------------------------------------------------------.
| yydefault -- do the default action for the current state.  |
`-----------------------------------------------------------*/
yydefault:
  yyn = yydefact[yystate];
  if (yyn == 0)
    goto yyerrlab;
  goto yyreduce;


/*-----------------------------.
| yyreduce -- Do a reduction.  |
`-----------------------------*/
yyreduce:
  /* yyn is the number of a rule to reduce with.  */
  yylen = yyr2[yyn];

  /* If YYLEN is nonzero, implement the default value of the action:
     `$$ = $1'.

     Otherwise, the following line sets YYVAL to garbage.
     This behavior is undocumented and Bison
     users should not rely upon it.  Assigning to YYVAL
     unconditionally makes the parser a bit smaller, and it avoids a
     GCC warning that YYVAL may be used uninitialized.  */
  yyval = yyvsp[1-yylen];

]b4_location_if(
[[  /* Default location. */
  YYLLOC_DEFAULT (yyloc, yylsp - yylen, yylen);]])[
  YY_REDUCE_PRINT (yyn);
  switch (yyn)
    ]{
      b4_actions
    }

/* Line __line__ of yacc.c.  */
b4_syncline([@oline@], [@ofile@])

[  yyvsp -= yylen;
  yyssp -= yylen;
]b4_location_if([  yylsp -= yylen;])[

  YY_STACK_PRINT (yyss, yyssp);

  *++yyvsp = yyval;
]b4_location_if([  *++yylsp = yyloc;])[

  /* 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 - YYNTOKENS] + *yyssp;
  if (0 <= yystate && yystate <= YYLAST && yycheck[yystate] == *yyssp)
    yystate = yytable[yystate];
  else
    yystate = yydefgoto[yyn - YYNTOKENS];

  goto yynewstate;


/*------------------------------------.
| yyerrlab -- here on detecting error |
`------------------------------------*/
yyerrlab:
  /* If not already recovering from an error, report this error.  */
  if (!yyerrstatus)
    {
      ++yynerrs;
#if YYERROR_VERBOSE
      yyn = yypact[yystate];

      if (YYPACT_NINF < yyn && yyn < YYLAST)
	{
	  YYSIZE_T yysize = 0;
	  int yytype = YYTRANSLATE (yychar);
	  const char* yyprefix;
	  char *yymsg;
	  int yyx;

	  /* Start YYX at -YYN if negative to avoid negative indexes in
	     YYCHECK.  */
	  int yyxbegin = yyn < 0 ? -yyn : 0;

	  /* Stay within bounds of both yycheck and yytname.  */
	  int yychecklim = YYLAST - yyn;
	  int yyxend = yychecklim < YYNTOKENS ? yychecklim : YYNTOKENS;
	  int yycount = 0;

	  yyprefix = ", expecting ";
	  for (yyx = yyxbegin; yyx < yyxend; ++yyx)
	    if (yycheck[yyx + yyn] == yyx && yyx != YYTERROR)
	      {
		yysize += yystrlen (yyprefix) + yystrlen (yytname [yyx]);
		yycount += 1;
		if (yycount == 5)
		  {
		    yysize = 0;
		    break;
		  }
	      }
	  yysize += (sizeof ("syntax error, unexpected ")
		     + yystrlen (yytname[yytype]));
	  yymsg = (char *) YYSTACK_ALLOC (yysize);
	  if (yymsg != 0)
	    {
	      char *yyp = yystpcpy (yymsg, "syntax error, unexpected ");
	      yyp = yystpcpy (yyp, yytname[yytype]);

	      if (yycount < 5)
		{
		  yyprefix = ", expecting ";
		  for (yyx = yyxbegin; yyx < yyxend; ++yyx)
		    if (yycheck[yyx + yyn] == yyx && yyx != YYTERROR)
		      {
			yyp = yystpcpy (yyp, yyprefix);
			yyp = yystpcpy (yyp, yytname[yyx]);
			yyprefix = " or ";
		      }
		}
	      yyerror (]b4_yyerror_args[yymsg);
	      YYSTACK_FREE (yymsg);
	    }
	  else
	    yyerror (]b4_yyerror_args["syntax error; also virtual memory exhausted");
	}
      else
#endif /* YYERROR_VERBOSE */
	yyerror (]b4_yyerror_args["syntax error");
    }

]b4_location_if([[  yyerror_range[0] = yylloc;]])[

  if (yyerrstatus == 3)
    {
      /* If just tried and failed to reuse look-ahead token after an
	 error, discard it.  */

      if (yychar <= YYEOF)
        {
          /* If at end of input, pop the error token,
	     then the rest of the stack, then return failure.  */
	  if (yychar == YYEOF)
	     for (;;)
	       {
]b4_location_if([[                 yyerror_range[0] = *yylsp;]])[
		 YYPOPSTACK;
		 if (yyssp == yyss)
		   YYABORT;
		 yydestruct ("Error: popping",
                             yystos[*yyssp], yyvsp]b4_location_if([, yylsp])[);
	       }
        }
      else
	{
	  yydestruct ("Error: discarding", yytoken, &yylval]b4_location_if([, &yylloc])[);
	  yychar = YYEMPTY;
	}
    }

  /* Else will try to reuse look-ahead token after shifting the error
     token.  */
  goto yyerrlab1;


/*---------------------------------------------------.
| yyerrorlab -- error raised explicitly by YYERROR.  |
`---------------------------------------------------*/
yyerrorlab:

#ifdef __GNUC__
  /* Pacify GCC when the user code never invokes YYERROR and the label
     yyerrorlab therefore never appears in user code.  */
  if (0)
     goto yyerrorlab;
#endif

]b4_location_if([[  yyerror_range[0] = yylsp[1-yylen];
  yylsp -= yylen;
  ]])[yyvsp -= yylen;
  yyssp -= yylen;
  yystate = *yyssp;
  goto yyerrlab1;


/*-------------------------------------------------------------.
| yyerrlab1 -- common code for both syntax error and YYERROR.  |
`-------------------------------------------------------------*/
yyerrlab1:
  yyerrstatus = 3;	/* Each real token shifted decrements this.  */

  for (;;)
    {
      yyn = yypact[yystate];
      if (yyn != YYPACT_NINF)
	{
	  yyn += YYTERROR;
	  if (0 <= yyn && yyn <= YYLAST && yycheck[yyn] == YYTERROR)
	    {
	      yyn = yytable[yyn];
	      if (0 < yyn)
		break;
	    }
	}

      /* Pop the current state because it cannot handle the error token.  */
      if (yyssp == yyss)
	YYABORT;

]b4_location_if([[      yyerror_range[0] = *yylsp;]])[
      yydestruct ("Error: popping", yystos[yystate], yyvsp]b4_location_if([, yylsp])[);
      YYPOPSTACK;
      yystate = *yyssp;
      YY_STACK_PRINT (yyss, yyssp);
    }

  if (yyn == YYFINAL)
    YYACCEPT;

  *++yyvsp = yylval;
]b4_location_if([[
  yyerror_range[1] = yylloc;
  /* Using YYLLOC is tempting, but would change the location of
     the look-ahead.  YYLOC is available though. */
  YYLLOC_DEFAULT (yyloc, yyerror_range - 1, 2);
  *++yylsp = yyloc;]])[

  /* Shift the error token. */
  YY_SYMBOL_PRINT ("Shifting", yystos[yyn], yyvsp, yylsp);

  yystate = yyn;
  goto yynewstate;


/*-------------------------------------.
| yyacceptlab -- YYACCEPT comes here.  |
`-------------------------------------*/
yyacceptlab:
  yyresult = 0;
  goto yyreturn;

/*-----------------------------------.
| yyabortlab -- YYABORT comes here.  |
`-----------------------------------*/
yyabortlab:
  yydestruct ("Error: discarding lookahead",
              yytoken, &yylval]b4_location_if([, &yylloc])[);
  yychar = YYEMPTY;
  yyresult = 1;
  goto yyreturn;

#ifndef yyoverflow
/*----------------------------------------------.
| yyoverflowlab -- parser overflow comes here.  |
`----------------------------------------------*/
yyoverflowlab:
  yyerror (]b4_yyerror_args["parser stack overflow");
  yyresult = 2;
  /* Fall through.  */
#endif

yyreturn:
#ifndef yyoverflow
  if (yyss != yyssa)
    YYSTACK_FREE (yyss);
#endif
  return yyresult;
]}


b4_epilogue
m4_if(b4_defines_flag, 0, [],
[@output @output_header_name@
b4_copyright([Skeleton parser for Yacc-like parsing with Bison],
             [1984, 1989, 1990, 2000, 2001, 2002, 2003, 2004])

/* As a special exception, when this file is copied by Bison into a
   Bison output file, you may use that output file without restriction.
   This special exception was added by the Free Software Foundation
   in version 1.24 of Bison.  */

b4_token_defines(b4_tokens)

#if ! defined (YYSTYPE) && ! defined (YYSTYPE_IS_DECLARED)
m4_ifdef([b4_stype],
[b4_syncline([b4_stype_line], [b4_filename])
typedef union m4_bregexp(b4_stype, [^{], [YYSTYPE ])b4_stype YYSTYPE;
/* Line __line__ of yacc.c.  */
b4_syncline([@oline@], [@ofile@])],
[typedef int YYSTYPE;])
# define yystype YYSTYPE /* obsolescent; will be withdrawn */
# define YYSTYPE_IS_DECLARED 1
# define YYSTYPE_IS_TRIVIAL 1
#endif

b4_pure_if([],
[extern YYSTYPE b4_prefix[]lval;])

b4_location_if(
[#if ! defined (YYLTYPE) && ! defined (YYLTYPE_IS_DECLARED)
typedef struct YYLTYPE
{
  int first_line;
  int first_column;
  int last_line;
  int last_column;
} YYLTYPE;
# define yyltype YYLTYPE /* obsolescent; will be withdrawn */
# define YYLTYPE_IS_DECLARED 1
# define YYLTYPE_IS_TRIVIAL 1
#endif

m4_if(b4_pure, [0],
[extern YYLTYPE b4_prefix[]lloc;])
])
])