cexp.c

这是完整的gcc源代码

    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;
}
#line 203 "./cexp.y"


/* During parsing of a C expression, the pointer to the next character
   is in this variable.  */

static char *lexptr;

/* Take care of parsing a number (anything that starts with a digit).
   Set yylval and return the token type; update lexptr.
   LEN is the number of characters in it.  */

/* maybe needs to actually deal with floating point numbers */

int
parse_number (olen)
     int olen;
{
  register char *p = lexptr;
  register long n = 0;
  register int c;
  register int base = 10;
  register int len = olen;

  for (c = 0; c < len; c++)
    if (p[c] == '.') {
      /* It's a float since it contains a point.  */
      yyerror ("floating point numbers not allowed in #if expressions");
      return ERROR;
    }

  yylval.integer.unsignedp = 0;

  if (len >= 3 && (!strncmp (p, "0x", 2) || !strncmp (p, "0X", 2))) {
    p += 2;
    base = 16;
    len -= 2;
  }
  else if (*p == '0')
    base = 8;

  while (len > 0) {
    c = *p++;
    len--;
    if (c >= 'A' && c <= 'Z') c += 'a' - 'A';

    if (c >= '0' && c <= '9') {
      n *= base;
      n += c - '0';
    } else if (base == 16 && c >= 'a' && c <= 'f') {
      n *= base;
      n += c - 'a' + 10;
    } else {
      /* `l' means long, and `u' means unsigned.  */
      while (1) {
	if (c == 'l' || c == 'L')
	  ;
	else if (c == 'u' || c == 'U')
	  yylval.integer.unsignedp = 1;
	else
	  break;

	if (len == 0)
	  break;
	c = *p++;
	len--;
      }
      /* Don't look for any more digits after the suffixes.  */
      break;
    }
  }

  if (len != 0) {
    yyerror ("Invalid number in #if expression");
    return ERROR;
  }

  /* If too big to be signed, consider it unsigned.  */
  if (n < 0)
    yylval.integer.unsignedp = 1;

  lexptr = p;
  yylval.integer.value = n;
  return INT;
}

struct token {
  char *operator;
  int token;
};

#ifndef NULL
#define NULL 0
#endif

static struct token tokentab2[] = {
  {"&&", AND},
  {"||", OR},
  {"<<", LSH},
  {">>", RSH},
  {"==", EQUAL},
  {"!=", NOTEQUAL},
  {"<=", LEQ},
  {">=", GEQ},
  {NULL, ERROR}
};

/* Read one token, getting characters through lexptr.  */

int
yylex ()
{
  register int c;
  register int namelen;
  register char *tokstart;
  register struct token *toktab;

 retry:

  tokstart = lexptr;
  c = *tokstart;
  /* See if it is a special token of length 2.  */
  for (toktab = tokentab2; toktab->operator != NULL; toktab++)
    if (c == *toktab->operator && tokstart[1] == toktab->operator[1]) {
      lexptr += 2;
      return toktab->token;
    }

  switch (c) {
  case 0:
    return 0;
    
  case ' ':
  case '\t':
  case '\r':
  case '\n':
    lexptr++;
    goto retry;
    
  case '\'':
    lexptr++;
    c = *lexptr++;
    if (c == '\\')
      c = parse_escape (&lexptr);

    /* Sign-extend the constant if chars are signed on target machine.  */
    {
      if (lookup ("__CHAR_UNSIGNED__", sizeof ("__CHAR_UNSIGNED__")-1, -1)
	  || ((c >> (CHAR_TYPE_SIZE - 1)) & 1) == 0)
	yylval.integer.value = c & ((1 << CHAR_TYPE_SIZE) - 1);
      else
	yylval.integer.value = c | ~((1 << CHAR_TYPE_SIZE) - 1);
    }

    yylval.integer.unsignedp = 0;
    c = *lexptr++;
    if (c != '\'') {
      yyerror ("Invalid character constant in #if");
      return ERROR;
    }
    
    return CHAR;

    /* some of these chars are invalid in constant expressions;
       maybe do something about them later */
  case '/':
  case '+':
  case '-':
  case '*':
  case '%':
  case '|':
  case '&':
  case '^':
  case '~':
  case '!':
  case '@':
  case '<':
  case '>':
  case '(':
  case ')':
  case '[':
  case ']':
  case '.':
  case '?':
  case ':':
  case '=':
  case '{':
  case '}':
  case ',':
    lexptr++;
    return c;
    
  case '"':
    yyerror ("double quoted strings not allowed in #if expressions");
    return ERROR;
  }
  if (c >= '0' && c <= '9') {
    /* It's a number */
    for (namelen = 0;
	 c = tokstart[namelen], is_idchar[c] || c == '.'; 
	 namelen++)
      ;
    return parse_number (namelen);
  }
  
  if (!is_idstart[c]) {
    yyerror ("Invalid token in expression");
    return ERROR;
  }
  
  /* It is a name.  See how long it is.  */
  
  for (namelen = 0; is_idchar[tokstart[namelen]]; namelen++)
    ;
  
  lexptr += namelen;
  return NAME;
}


/* Parse a C escape sequence.  STRING_PTR points to a variable
   containing a pointer to the string to parse.  That pointer
   is updated past the characters we use.  The value of the
   escape sequence is returned.

   A negative value means the sequence \ newline was seen,
   which is supposed to be equivalent to nothing at all.

   If \ is followed by a null character, we return a negative
   value and leave the string pointer pointing at the null character.

   If \ is followed by 000, we return 0 and leave the string pointer
   after the zeros.  A value of 0 does not mean end of string.  */

int
parse_escape (string_ptr)
     char **string_ptr;
{
  register int c = *(*string_ptr)++;
  switch (c)
    {
    case 'a':
      return TARGET_BELL;
    case 'b':
      return TARGET_BS;
    case 'e':
      return 033;
    case 'f':
      return TARGET_FF;
    case 'n':
      return TARGET_NEWLINE;
    case 'r':
      return TARGET_CR;
    case 't':
      return TARGET_TAB;
    case 'v':
      return TARGET_VT;
    case '\n':
      return -2;
    case 0:
      (*string_ptr)--;
      return 0;
    case '^':
      c = *(*string_ptr)++;
      if (c == '\\')
	c = parse_escape (string_ptr);
      if (c == '?')
	return 0177;
      return (c & 0200) | (c & 037);
      
    case '0':
    case '1':
    case '2':
    case '3':
    case '4':
    case '5':
    case '6':
    case '7':
      {
	register int i = c - '0';
	register int count = 0;
	while (++count < 3)
	  {
	    c = *(*string_ptr)++;
	    if (c >= '0' && c <= '7')
	      i = (i << 3) + c - '0';
	    else
	      {
		(*string_ptr)--;
		break;
	      }
	  }
	if ((i & ~((1 << CHAR_TYPE_SIZE) - 1)) != 0)
	  {
	    i &= (1 << CHAR_TYPE_SIZE) - 1;
	    warning ("octal character constant does not fit in a byte");
	  }
	return i;
      }
    case 'x':
      {
	register int i = 0;
	register int count = 0;
	for (;;)
	  {
	    c = *(*string_ptr)++;
	    if (c >= '0' && c <= '9')
	      i = (i << 4) + c - '0';
	    else if (c >= 'a' && c <= 'f')
	      i = (i << 4) + c - 'a' + 10;
	    else if (c >= 'A' && c <= 'F')
	      i = (i << 4) + c - 'A' + 10;
	    else
	      {
		(*string_ptr)--;
		break;
	      }
	  }
	if ((i & ~((1 << BITS_PER_UNIT) - 1)) != 0)
	  {
	    i &= (1 << BITS_PER_UNIT) - 1;
	    warning ("hex character constant does not fit in a byte");
	  }
	return i;
      }
    default:
      return c;
    }
}

void
yyerror (s)
     char *s;
{
  error (s);
  longjmp (parse_return_error, 1);
}

/* This page contains the entry point to this file.  */

/* Parse STRING as an expression, and complain if this fails
   to use up all of the contents of STRING.  */
/* We do not support C comments.  They should be removed before
   this function is called.  */

int
parse_c_expression (string)
     char *string;
{
  lexptr = string;
  
  if (lexptr == 0 || *lexptr == 0) {
    error ("empty #if expression");
    return 0;			/* don't include the #if group */
  }

  /* if there is some sort of scanning error, just return 0 and assume
     the parsing routine has printed an error message somewhere.
     there is surely a better thing to do than this.     */
  if (setjmp (parse_return_error))
    return 0;

  if (yyparse ())
    return 0;			/* actually this is never reached
				   the way things stand. */
  if (*lexptr)
    error ("Junk after end of expression.");

  return expression_value;	/* set by yyparse () */
}

#ifdef TEST_EXP_READER
/* main program, for testing purposes. */
main ()
{
  int n, c;
  char buf[1024];
  extern int yydebug;
/*
  yydebug = 1;
*/
  initialize_random_junk ();

  for (;;) {
    printf ("enter expression: ");
    n = 0;
    while ((buf[n] = getchar ()) != '\n' && buf[n] != EOF)
      n++;
    if (buf[n] == EOF)
      break;
    buf[n] = '\0';
    printf ("parser returned %d\n", parse_c_expression (buf));
  }
}

/* table to tell if char can be part of a C identifier. */
unsigned char is_idchar[256];
/* table to tell if char can be first char of a c identifier. */
unsigned char is_idstart[256];
/* table to tell if c is horizontal space.  isspace () thinks that
   newline is space; this is not a good idea for this program. */
char is_hor_space[256];

/*
 * initialize random junk in the hash table and maybe other places
 */
initialize_random_junk ()
{
  register int i;

  /*
   * Set up is_idchar and is_idstart tables.  These should be
   * faster than saying (is_alpha (c) || c == '_'), etc.
   * Must do set up these things before calling any routines tthat
   * refer to them.
   */
  for (i = 'a'; i <= 'z'; i++) {
    ++is_idchar[i - 'a' + 'A'];
    ++is_idchar[i];
    ++is_idstart[i - 'a' + 'A'];
    ++is_idstart[i];
  }
  for (i = '0'; i <= '9'; i++)
    ++is_idchar[i];
  ++is_idchar['_'];
  ++is_idstart['_'];
#if DOLLARS_IN_IDENTIFIERS
  ++is_idchar['$'];
  ++is_idstart['$'];
#endif

  /* horizontal space table */
  ++is_hor_space[' '];
  ++is_hor_space['\t'];
}

error (msg)
{
  printf ("error: %s\n", msg);
}

warning (msg)
{
  printf ("warning: %s\n", msg);
}

struct hashnode *
lookup (name, len, hash)
     char *name;
     int len;
     int hash;
{
  return (DEFAULT_SIGNED_CHAR) ? 0 : ((struct hashnode *) -1);
}
#endif