c-typeck.c

gcc库的原代码,对编程有很大帮助.

  /* See if there is a field or component with name COMPONENT.  */

  if (code == RECORD_TYPE || code == UNION_TYPE)
    {
      tree indirect = 0;

      if (TYPE_SIZE (type) == 0)
	{
	  incomplete_type_error (NULL_TREE, type);
	  return error_mark_node;
	}

      field = lookup_field (type, component, &indirect);

      if (!field)
	{
	  error (code == RECORD_TYPE
		 ? "structure has no member named `%s'"
		 : "union has no member named `%s'",
		 IDENTIFIER_POINTER (component));
	  return error_mark_node;
	}
      if (TREE_TYPE (field) == error_mark_node)
	return error_mark_node;

      /* If FIELD was found buried within an anonymous union,
	 make one COMPONENT_REF to get that anonymous union,
	 then fall thru to make a second COMPONENT_REF to get FIELD.  */
      if (indirect != 0)
	{
	  ref = build (COMPONENT_REF, TREE_TYPE (indirect), datum, indirect);
	  if (TREE_READONLY (datum) || TREE_READONLY (indirect))
	    TREE_READONLY (ref) = 1;
	  if (TREE_THIS_VOLATILE (datum) || TREE_THIS_VOLATILE (indirect))
	    TREE_THIS_VOLATILE (ref) = 1;
	  datum = ref;
	}

      ref = build (COMPONENT_REF, TREE_TYPE (field), datum, field);

      if (TREE_READONLY (datum) || TREE_READONLY (field))
	TREE_READONLY (ref) = 1;
      if (TREE_THIS_VOLATILE (datum) || TREE_THIS_VOLATILE (field))
	TREE_THIS_VOLATILE (ref) = 1;

      return ref;
    }
  else if (code != ERROR_MARK)
    error ("request for member `%s' in something not a structure or union",
	    IDENTIFIER_POINTER (component));

  return error_mark_node;
}

/* Given an expression PTR for a pointer, return an expression
   for the value pointed to.
   ERRORSTRING is the name of the operator to appear in error messages.  */

tree
build_indirect_ref (ptr, errorstring)
     tree ptr;
     char *errorstring;
{
  register tree pointer = default_conversion (ptr);
  register tree type = TREE_TYPE (pointer);

  if (TREE_CODE (type) == POINTER_TYPE)
    {
      if (TREE_CODE (pointer) == ADDR_EXPR
	  && !flag_volatile
	  && (TREE_TYPE (TREE_OPERAND (pointer, 0))
	      == TREE_TYPE (type)))
	return TREE_OPERAND (pointer, 0);
      else
	{
	  tree t = TREE_TYPE (type);
	  register tree ref = build1 (INDIRECT_REF,
				      TYPE_MAIN_VARIANT (t), pointer);

	  if (TYPE_SIZE (t) == 0 && TREE_CODE (t) != ARRAY_TYPE)
	    {
	      error ("dereferencing pointer to incomplete type");
	      return error_mark_node;
	    }
	  if (TREE_CODE (t) == VOID_TYPE)
	    warning ("dereferencing `void *' pointer");

	  /* We *must* set TREE_READONLY when dereferencing a pointer to const,
	     so that we get the proper error message if the result is used
	     to assign to.  Also, &* is supposed to be a no-op.
	     And ANSI C seems to specify that the type of the result
	     should be the const type.  */
	  /* A de-reference of a pointer to const is not a const.  It is valid
	     to change it via some other pointer.  */
	  TREE_READONLY (ref) = TYPE_READONLY (t);
	  TREE_SIDE_EFFECTS (ref)
	    = TYPE_VOLATILE (t) || TREE_SIDE_EFFECTS (pointer) || flag_volatile;
	  TREE_THIS_VOLATILE (ref) = TYPE_VOLATILE (t);
	  return ref;
	}
    }
  else if (TREE_CODE (pointer) != ERROR_MARK)
    error ("invalid type argument of `%s'", errorstring);
  return error_mark_node;
}

/* This handles expressions of the form "a[i]", which denotes
   an array reference.

   This is logically equivalent in C to *(a+i), but we may do it differently.
   If A is a variable or a member, we generate a primitive ARRAY_REF.
   This avoids forcing the array out of registers, and can work on
   arrays that are not lvalues (for example, members of structures returned
   by functions).  */

tree
build_array_ref (array, index)
     tree array, index;
{
  if (index == 0)
    {
      error ("subscript missing in array reference");
      return error_mark_node;
    }

  if (TREE_TYPE (array) == error_mark_node
      || TREE_TYPE (index) == error_mark_node)
    return error_mark_node;

  if (TREE_CODE (TREE_TYPE (array)) == ARRAY_TYPE
      && TREE_CODE (array) != INDIRECT_REF)
    {
      tree rval, type;

      /* Subscripting with type char is likely to lose
	 on a machine where chars are signed.
	 So warn on any machine, but optionally.
	 Don't warn for unsigned char since that type is safe.
	 Don't warn for signed char because anyone who uses that
	 must have done so deliberately.  */
      if (warn_char_subscripts
	  && TYPE_MAIN_VARIANT (TREE_TYPE (index)) == char_type_node)
	warning ("array subscript has type `char'");

      /* Apply default promotions *after* noticing character types.  */
      index = default_conversion (index);

      /* Require integer *after* promotion, for sake of enums.  */
      if (TREE_CODE (TREE_TYPE (index)) != INTEGER_TYPE)
	{
	  error ("array subscript is not an integer");
	  return error_mark_node;
	}

      /* An array that is indexed by a non-constant
	 cannot be stored in a register; we must be able to do
	 address arithmetic on its address.
	 Likewise an array of elements of variable size.  */
      if (TREE_CODE (index) != INTEGER_CST
	  || (TYPE_SIZE (TREE_TYPE (TREE_TYPE (array))) != 0
	      && TREE_CODE (TYPE_SIZE (TREE_TYPE (TREE_TYPE (array)))) != INTEGER_CST))
	{
	  if (mark_addressable (array) == 0)
	    return error_mark_node;
	}
      /* An array that is indexed by a constant value which is not within
	 the array bounds cannot be stored in a register either; because we
	 would get a crash in store_bit_field/extract_bit_field when trying
	 to access a non-existent part of the register.  */
      if (TREE_CODE (index) == INTEGER_CST
	  && TYPE_VALUES (TREE_TYPE (array))
	  && ! int_fits_type_p (index, TYPE_VALUES (TREE_TYPE (array))))
	{
	  if (mark_addressable (array) == 0)
	    return error_mark_node;
	}

      if (pedantic && !lvalue_p (array))
	{
	  if (DECL_REGISTER (array))
	    pedwarn ("ANSI C forbids subscripting `register' array");
	  else
	    pedwarn ("ANSI C forbids subscripting non-lvalue array");
	}

      if (pedantic)
	{
	  tree foo = array;
	  while (TREE_CODE (foo) == COMPONENT_REF)
	    foo = TREE_OPERAND (foo, 0);
	  if (TREE_CODE (foo) == VAR_DECL && DECL_REGISTER (foo))
	    pedwarn ("ANSI C forbids subscripting non-lvalue array");
	}

      type = TYPE_MAIN_VARIANT (TREE_TYPE (TREE_TYPE (array)));
      rval = build (ARRAY_REF, type, array, index);
      /* Array ref is const/volatile if the array elements are
         or if the array is.  */
      TREE_READONLY (rval)
	|= (TYPE_READONLY (TREE_TYPE (TREE_TYPE (array)))
	    | TREE_READONLY (array));
      TREE_SIDE_EFFECTS (rval)
	|= (TYPE_VOLATILE (TREE_TYPE (TREE_TYPE (array)))
	    | TREE_SIDE_EFFECTS (array));
      TREE_THIS_VOLATILE (rval)
	|= (TYPE_VOLATILE (TREE_TYPE (TREE_TYPE (array)))
	    /* This was added by rms on 16 Nov 91.
	       It fixes  vol struct foo *a;  a->elts[1] 
	       in an inline function.
	       Hope it doesn't break something else.  */
	    | TREE_THIS_VOLATILE (array));
      return require_complete_type (fold (rval));
    }

  {
    tree ar = default_conversion (array);
    tree ind = default_conversion (index);

    /* Put the integer in IND to simplify error checking.  */
    if (TREE_CODE (TREE_TYPE (ar)) == INTEGER_TYPE)
      {
	tree temp = ar;
	ar = ind;
	ind = temp;
      }

    if (ar == error_mark_node)
      return ar;

    if (TREE_CODE (TREE_TYPE (ar)) != POINTER_TYPE)
      {
	error ("subscripted value is neither array nor pointer");
	return error_mark_node;
      }
    if (TREE_CODE (TREE_TYPE (ind)) != INTEGER_TYPE)
      {
	error ("array subscript is not an integer");
	return error_mark_node;
      }

    return build_indirect_ref (build_binary_op (PLUS_EXPR, ar, ind, 0),
			       "array indexing");
  }
}

/* Build a function call to function FUNCTION with parameters PARAMS.
   PARAMS is a list--a chain of TREE_LIST nodes--in which the
   TREE_VALUE of each node is a parameter-expression.
   FUNCTION's data type may be a function type or a pointer-to-function.  */

tree
build_function_call (function, params)
     tree function, params;
{
  register tree fntype, fundecl = 0;
  register tree coerced_params;
  tree name = NULL_TREE, assembler_name = NULL_TREE;

  /* Strip NON_LVALUE_EXPRs, etc., since we aren't using as an lvalue.  */
  STRIP_TYPE_NOPS (function);

  /* Convert anything with function type to a pointer-to-function.  */
  if (TREE_CODE (function) == FUNCTION_DECL)
    {
      name = DECL_NAME (function);
      assembler_name = DECL_ASSEMBLER_NAME (function);

      /* Differs from default_conversion by not setting TREE_ADDRESSABLE
	 (because calling an inline function does not mean the function
	 needs to be separately compiled).  */
      fntype = build_type_variant (TREE_TYPE (function),
				   TREE_READONLY (function),
				   TREE_THIS_VOLATILE (function));
      fundecl = function;
      function = build1 (ADDR_EXPR, build_pointer_type (fntype), function);
    }
  else
    function = default_conversion (function);

  fntype = TREE_TYPE (function);

  if (TREE_CODE (fntype) == ERROR_MARK)
    return error_mark_node;

  if (!(TREE_CODE (fntype) == POINTER_TYPE
	&& TREE_CODE (TREE_TYPE (fntype)) == FUNCTION_TYPE))
    {
      error ("called object is not a function");
      return error_mark_node;
    }

  /* fntype now gets the type of function pointed to.  */
  fntype = TREE_TYPE (fntype);

  /* Convert the parameters to the types declared in the
     function prototype, or apply default promotions.  */

  coerced_params
    = convert_arguments (TYPE_ARG_TYPES (fntype), params, name, fundecl);

  /* Check for errors in format strings.  */

  if (warn_format && (name || assembler_name))
    check_function_format (name, assembler_name, coerced_params);

  /* Recognize certain built-in functions so we can make tree-codes
     other than CALL_EXPR.  We do this when it enables fold-const.c
     to do something useful.  */

  if (TREE_CODE (function) == ADDR_EXPR
      && TREE_CODE (TREE_OPERAND (function, 0)) == FUNCTION_DECL
      && DECL_BUILT_IN (TREE_OPERAND (function, 0)))
    switch (DECL_FUNCTION_CODE (TREE_OPERAND (function, 0)))
      {
      case BUILT_IN_ABS:
      case BUILT_IN_LABS:
      case BUILT_IN_FABS:
	if (coerced_params == 0)
	  return integer_zero_node;
	return build_unary_op (ABS_EXPR, TREE_VALUE (coerced_params), 0);
      }

  {
    register tree result
      = build (CALL_EXPR, TREE_TYPE (fntype),
	       function, coerced_params, NULL_TREE);

    TREE_SIDE_EFFECTS (result) = 1;
    if (TREE_TYPE (result) == void_type_node)
      return result;
    return require_complete_type (result);
  }
}

/* Convert the argument expressions in the list VALUES
   to the types in the list TYPELIST.  The result is a list of converted
   argument expressions.

   If TYPELIST is exhausted, or when an element has NULL as its type,
   perform the default conversions.

   PARMLIST is the chain of parm decls for the function being called.
   It may be 0, if that info is not available.
   It is used only for generating error messages.

   NAME is an IDENTIFIER_NODE or 0.  It is used only for error messages.

   This is also where warnings about wrong number of args are generated.

   Both VALUES and the returned value are chains of TREE_LIST nodes
   with the elements of the list in the TREE_VALUE slots of those nodes.  */

static tree
convert_arguments (typelist, values, name, fundecl)
     tree typelist, values, name, fundecl;
{
  register tree typetail, valtail;
  register tree result = NULL;
  int parmnum;

  /* Scan the given expressions and types, producing individual
     converted arguments and pushing them on RESULT in reverse order.  */

  for (valtail = values, typetail = typelist, parmnum = 0;
       valtail;
       valtail = TREE_CHAIN (valtail), parmnum++)
    {
      register tree type = typetail ? TREE_VALUE (typetail) : 0;
      register tree val = TREE_VALUE (valtail);

      if (type == void_type_node)
	{
	  if (name)
	    error ("too many arguments to function `%s'",
		   IDENTIFIER_POINTER (name));
	  else
	    error ("too many arguments to function");
	  break;
	}

      /* Strip NON_LVALUE_EXPRs since we aren't using as an lvalue.  */
      /* Do not use STRIP_NOPS here!  We do not want an enumerator with value 0
	 to convert automatically to a pointer.  */
      if (TREE_CODE (val) == NON_LVALUE_EXPR)
	val = TREE_OPERAND (val, 0);

      if (TREE_CODE (TREE_TYPE (val)) == ARRAY_TYPE
	  || TREE_CODE (TREE_TYPE (val)) == FUNCTION_TYPE)
	val = default_conversion (val);

      val = require_complete_type (val);

      if (type != 0)
	{
	  /* Formal parm type is specified by a function prototype.  */
	  tree parmval;

	  if (TYPE_SIZE (type) == 0)
	    {
	      error ("type of formal parameter %d is incomplete", parmnum + 1);
	      parmval = val;
	    }
	  else
	    {
	      /* Optionally warn about conversions that
		 differ from the default conversions.  */
	      if (warn_conversion)
		{
		  int formal_prec = TYPE_PRECISION (type);

		  if (INTEGRAL_TYPE_P (type)
		      && TREE_CODE (TREE_TYPE (val)) == REAL_TYPE)
		    warn_for_assignment ("%s as integer rather than floating due to prototype", (char *) 0, name, parmnum + 1);
		  else if (TREE_CODE (type) == COMPLEX_TYPE
			   && TREE_CODE (TREE_TYPE (val)) == REAL_TYPE)