c-lex.c

gcc库的原代码,对编程有很大帮助.

	      bytes = TYPE_PRECISION (long_long_integer_type_node) / 8;
	    else
	      bytes = TYPE_PRECISION (long_integer_type_node) / 8;

	    warn = overflow;
	    for (i = bytes; i < TOTAL_PARTS; i++)
	      if (parts[i])
		warn = 1;
	    if (warn)
	      pedwarn ("integer constant out of range");

	    /* This is simplified by the fact that our constant
	       is always positive.  */

	    high = low = 0;

	    for (i = 0; i < HOST_BITS_PER_WIDE_INT / HOST_BITS_PER_CHAR; i++)
	      {
		high |= ((HOST_WIDE_INT) parts[i + (HOST_BITS_PER_WIDE_INT
						    / HOST_BITS_PER_CHAR)]
			 << (i * HOST_BITS_PER_CHAR));
		low |= (HOST_WIDE_INT) parts[i] << (i * HOST_BITS_PER_CHAR);
	      }
	    
	    yylval.ttype = build_int_2 (low, high);
	    TREE_TYPE (yylval.ttype) = long_long_unsigned_type_node;

	    /* If warn_traditional, calculate both the ANSI type and the
	       traditional type, then see if they disagree.
	       Otherwise, calculate only the type for the dialect in use.  */
	    if (warn_traditional || flag_traditional)
	      {
		/* Calculate the traditional type.  */
		/* Traditionally, any constant is signed;
		   but if unsigned is specified explicitly, obey that.
		   Use the smallest size with the right number of bits,
		   except for one special case with decimal constants.  */
		if (! spec_long && base != 10
		    && int_fits_type_p (yylval.ttype, unsigned_type_node))
		  traditional_type = (spec_unsigned ? unsigned_type_node
				      : integer_type_node);
		/* A decimal constant must be long
		   if it does not fit in type int.
		   I think this is independent of whether
		   the constant is signed.  */
		else if (! spec_long && base == 10
			 && int_fits_type_p (yylval.ttype, integer_type_node))
		  traditional_type = (spec_unsigned ? unsigned_type_node
				      : integer_type_node);
		else if (! spec_long_long)
		  traditional_type = (spec_unsigned ? long_unsigned_type_node
				      : long_integer_type_node);
		else
		  traditional_type = (spec_unsigned
				      ? long_long_unsigned_type_node
				      : long_long_integer_type_node);
	      }
	    if (warn_traditional || ! flag_traditional)
	      {
		/* Calculate the ANSI type.  */
		if (! spec_long && ! spec_unsigned
		    && int_fits_type_p (yylval.ttype, integer_type_node))
		  ansi_type = integer_type_node;
		else if (! spec_long && (base != 10 || spec_unsigned)
			 && int_fits_type_p (yylval.ttype, unsigned_type_node))
		  ansi_type = unsigned_type_node;
		else if (! spec_unsigned && !spec_long_long
			 && int_fits_type_p (yylval.ttype, long_integer_type_node))
		  ansi_type = long_integer_type_node;
		else if (! spec_long_long)
		  ansi_type = long_unsigned_type_node;
		else if (! spec_unsigned
			 /* Verify value does not overflow into sign bit.  */
			 && TREE_INT_CST_HIGH (yylval.ttype) >= 0
			 && int_fits_type_p (yylval.ttype,
					     long_long_integer_type_node))
		  ansi_type = long_long_integer_type_node;
		else
		  ansi_type = long_long_unsigned_type_node;
	      }

	    type = flag_traditional ? traditional_type : ansi_type;

	    if (warn_traditional && traditional_type != ansi_type)
	      {
		if (TYPE_PRECISION (traditional_type)
		    != TYPE_PRECISION (ansi_type))
		  warning ("width of integer constant changes with -traditional");
		else if (TREE_UNSIGNED (traditional_type)
			 != TREE_UNSIGNED (ansi_type))
		  warning ("integer constant is unsigned in ANSI C, signed with -traditional");
		else
		  warning ("width of integer constant may change on other systems with -traditional");
	      }

	    if (!flag_traditional && !int_fits_type_p (yylval.ttype, type)
		&& !warn)
	      pedwarn ("integer constant out of range");

	    if (base == 10 && ! spec_unsigned && TREE_UNSIGNED (type))
	      warning ("decimal constant is so large that it is unsigned");

	    if (spec_imag)
	      {
		if (TYPE_PRECISION (type)
		    <= TYPE_PRECISION (integer_type_node))
		  yylval.ttype
		    = build_complex (integer_zero_node,
				     convert (integer_type_node, yylval.ttype));
		else
		  error ("complex integer constant is too wide for `complex int'");
	      }
	    else if (flag_traditional && !int_fits_type_p (yylval.ttype, type))
	      /* The traditional constant 0x80000000 is signed
		 but doesn't fit in the range of int.
		 This will change it to -0x80000000, which does fit.  */
	      {
		TREE_TYPE (yylval.ttype) = unsigned_type (type);
		yylval.ttype = convert (type, yylval.ttype);
		TREE_OVERFLOW (yylval.ttype)
		  = TREE_CONSTANT_OVERFLOW (yylval.ttype) = 0;
	      }
	    else
	      TREE_TYPE (yylval.ttype) = type;

	    *p = 0;
	  }

	value = CONSTANT; break;
      }

    case '\'':
    char_constant:
      {
	register int result = 0;
	register int num_chars = 0;
	unsigned width = TYPE_PRECISION (char_type_node);
	int max_chars;

	if (wide_flag)
	  {
	    width = WCHAR_TYPE_SIZE;
#ifdef MULTIBYTE_CHARS
	    max_chars = MB_CUR_MAX;
#else
	    max_chars = 1;
#endif
	  }
	else
	  max_chars = TYPE_PRECISION (integer_type_node) / width;

	while (1)
	  {
	  tryagain:

	    c = getc (finput);

	    if (c == '\'' || c == EOF)
	      break;

	    if (c == '\\')
	      {
		int ignore = 0;
		c = readescape (&ignore);
		if (ignore)
		  goto tryagain;
		if (width < HOST_BITS_PER_INT
		    && (unsigned) c >= (1 << width))
		  pedwarn ("escape sequence out of range for character");
#ifdef MAP_CHARACTER
		if (isprint (c))
		  c = MAP_CHARACTER (c);
#endif
	      }
	    else if (c == '\n')
	      {
		if (pedantic)
		  pedwarn ("ANSI C forbids newline in character constant");
		lineno++;
	      }
#ifdef MAP_CHARACTER
	    else
	      c = MAP_CHARACTER (c);
#endif

	    num_chars++;
	    if (num_chars > maxtoken - 4)
	      extend_token_buffer (token_buffer);

	    token_buffer[num_chars] = c;

	    /* Merge character into result; ignore excess chars.  */
	    if (num_chars < max_chars + 1)
	      {
		if (width < HOST_BITS_PER_INT)
		  result = (result << width) | (c & ((1 << width) - 1));
		else
		  result = c;
	      }
	  }

	token_buffer[num_chars + 1] = '\'';
	token_buffer[num_chars + 2] = 0;

	if (c != '\'')
	  error ("malformatted character constant");
	else if (num_chars == 0)
	  error ("empty character constant");
	else if (num_chars > max_chars)
	  {
	    num_chars = max_chars;
	    error ("character constant too long");
	  }
	else if (num_chars != 1 && ! flag_traditional)
	  warning ("multi-character character constant");

	/* If char type is signed, sign-extend the constant.  */
	if (! wide_flag)
	  {
	    int num_bits = num_chars * width;
	    if (num_bits == 0)
	      /* We already got an error; avoid invalid shift.  */
	      yylval.ttype = build_int_2 (0, 0);
	    else if (TREE_UNSIGNED (char_type_node)
		     || ((result >> (num_bits - 1)) & 1) == 0)
	      yylval.ttype
		= build_int_2 (result & ((unsigned HOST_WIDE_INT) ~0
					 >> (HOST_BITS_PER_WIDE_INT - num_bits)),
			       0);
	    else
	      yylval.ttype
		= build_int_2 (result | ~((unsigned HOST_WIDE_INT) ~0
					  >> (HOST_BITS_PER_WIDE_INT - num_bits)),
			       -1);
	    TREE_TYPE (yylval.ttype) = integer_type_node;
	  }
	else
	  {
#ifdef MULTIBYTE_CHARS
	    /* Set the initial shift state and convert the next sequence.  */
	    result = 0;
	    /* In all locales L'\0' is zero and mbtowc will return zero,
	       so don't use it.  */
	    if (num_chars > 1
		|| (num_chars == 1 && token_buffer[1] != '\0'))
	      {
		wchar_t wc;
		(void) mbtowc (NULL_PTR, NULL_PTR, 0);
		if (mbtowc (& wc, token_buffer + 1, num_chars) == num_chars)
		  result = wc;
		else
		  warning ("Ignoring invalid multibyte character");
	      }
#endif
	    yylval.ttype = build_int_2 (result, 0);
	    TREE_TYPE (yylval.ttype) = wchar_type_node;
	  }

	value = CONSTANT;
	break;
      }

    case '"':
    string_constant:
      {
	c = getc (finput);
	p = token_buffer + 1;

	while (c != '"' && c >= 0)
	  {
	    if (c == '\\')
	      {
		int ignore = 0;
		c = readescape (&ignore);
		if (ignore)
		  goto skipnewline;
		if (!wide_flag
		    && TYPE_PRECISION (char_type_node) < HOST_BITS_PER_INT
		    && c >= (1 << TYPE_PRECISION (char_type_node)))
		  pedwarn ("escape sequence out of range for character");
	      }
	    else if (c == '\n')
	      {
		if (pedantic)
		  pedwarn ("ANSI C forbids newline in string constant");
		lineno++;
	      }

	    if (p == token_buffer + maxtoken)
	      p = extend_token_buffer (p);
	    *p++ = c;

	  skipnewline:
	    c = getc (finput);
	  }
	*p = 0;

	if (c < 0)
	  error ("Unterminated string constant");

	/* We have read the entire constant.
	   Construct a STRING_CST for the result.  */

	if (wide_flag)
	  {
	    /* If this is a L"..." wide-string, convert the multibyte string
	       to a wide character string.  */
	    char *widep = (char *) alloca ((p - token_buffer) * WCHAR_BYTES);
	    int len;

#ifdef MULTIBYTE_CHARS
	    len = mbstowcs ((wchar_t *) widep, token_buffer + 1, p - token_buffer);
	    if (len < 0 || len >= (p - token_buffer))
	      {
		warning ("Ignoring invalid multibyte string");
		len = 0;
	      }
	    bzero (widep + (len * WCHAR_BYTES), WCHAR_BYTES);
#else
	    {
	      union { long l; char c[sizeof (long)]; } u;
	      int big_endian;
	      char *wp, *cp;

	      /* Determine whether host is little or big endian.  */
	      u.l = 1;
	      big_endian = u.c[sizeof (long) - 1];
	      wp = widep + (big_endian ? WCHAR_BYTES - 1 : 0);

	      bzero (widep, (p - token_buffer) * WCHAR_BYTES);
	      for (cp = token_buffer + 1; cp < p; cp++)
		*wp = *cp, wp += WCHAR_BYTES;
	      len = p - token_buffer - 1;
	    }
#endif
	    yylval.ttype = build_string ((len + 1) * WCHAR_BYTES, widep);
	    TREE_TYPE (yylval.ttype) = wchar_array_type_node;
	    value = STRING;
	  }
	else if (objc_flag)
	  {
	    extern tree build_objc_string();
	    /* Return an Objective-C @"..." constant string object.  */
	    yylval.ttype = build_objc_string (p - token_buffer,
					      token_buffer + 1);
	    TREE_TYPE (yylval.ttype) = char_array_type_node;
	    value = OBJC_STRING;
	  }
	else
	  {
	    yylval.ttype = build_string (p - token_buffer, token_buffer + 1);
	    TREE_TYPE (yylval.ttype) = char_array_type_node;
	    value = STRING;
	  }

	*p++ = '"';
	*p = 0;

	break;
      }

    case '+':
    case '-':
    case '&':
    case '|':
    case ':':
    case '<':
    case '>':
    case '*':
    case '/':
    case '%':
    case '^':
    case '!':
    case '=':
      {
	register int c1;

      combine:

	switch (c)
	  {
	  case '+':
	    yylval.code = PLUS_EXPR; break;
	  case '-':
	    yylval.code = MINUS_EXPR; break;
	  case '&':
	    yylval.code = BIT_AND_EXPR; break;
	  case '|':
	    yylval.code = BIT_IOR_EXPR; break;
	  case '*':
	    yylval.code = MULT_EXPR; break;
	  case '/':
	    yylval.code = TRUNC_DIV_EXPR; break;
	  case '%':
	    yylval.code = TRUNC_MOD_EXPR; break;
	  case '^':
	    yylval.code = BIT_XOR_EXPR; break;
	  case LSHIFT:
	    yylval.code = LSHIFT_EXPR; break;
	  case RSHIFT:
	    yylval.code = RSHIFT_EXPR; break;
	  case '<':
	    yylval.code = LT_EXPR; break;
	  case '>':
	    yylval.code = GT_EXPR; break;
	  }

	token_buffer[1] = c1 = getc (finput);
	token_buffer[2] = 0;

	if (c1 == '=')
	  {
	    switch (c)
	      {
	      case '<':
		value = ARITHCOMPARE; yylval.code = LE_EXPR; goto done;
	      case '>':
		value = ARITHCOMPARE; yylval.code = GE_EXPR; goto done;
	      case '!':
		value = EQCOMPARE; yylval.code = NE_EXPR; goto done;
	      case '=':
		value = EQCOMPARE; yylval.code = EQ_EXPR; goto done;
	      }
	    value = ASSIGN; goto done;
	  }
	else if (c == c1)
	  switch (c)
	    {
	    case '+':
	      value = PLUSPLUS; goto done;
	    case '-':
	      value = MINUSMINUS; goto done;
	    case '&':
	      value = ANDAND; goto done;
	    case '|':
	      value = OROR; goto done;
	    case '<':
	      c = LSHIFT;
	      goto combine;
	    case '>':
	      c = RSHIFT;
	      goto combine;
	    }
	else
	  switch (c)
	    {
	    case '-':
	      if (c1 == '>')
		{ value = POINTSAT; goto done; }
	      break;
	    case ':':
	      if (c1 == '>')
		{ value = ']'; goto done; }
	      break;
	    case '<':
	      if (c1 == '%')
		{ value = '{'; goto done; }
	      if (c1 == ':')
		{ value = '['; goto done; }
	      break;
	    case '%':
	      if (c1 == '>')
		{ value = '}'; goto done; }
	      break;
	    }
	ungetc (c1, finput);
	token_buffer[1] = 0;

	if ((c == '<') || (c == '>'))
	  value = ARITHCOMPARE;
	else value = c;
	goto done;
      }

    case 0:
      /* Don't make yyparse think this is eof.  */
      value = 1;
      break;

    default:
      value = c;
    }

done:
/*  yylloc.last_line = lineno; */

  return value;
}

/* Sets the value of the 'yydebug' variable to VALUE.
   This is a function so we don't have to have YYDEBUG defined
   in order to build the compiler.  */

void
set_yydebug (value)
     int value;
{
#if YYDEBUG != 0
  yydebug = value;
#else
  warning ("YYDEBUG not defined.");
#endif
}