typeck.c

gcc库的原代码,对编程有很大帮助.

        In that case we should be able to do better.  */
  if (IS_SIGNATURE (type))
    {
      error ("`__alignof' applied to a signature type");
      return size_int (1);
    }

  t = size_int (TYPE_ALIGN (type) / BITS_PER_UNIT);
  force_fit_type (t, 0);
  return t;
}

/* Perform default promotions for C data used in expressions.
   Arrays and functions are converted to pointers;
   enumeral types or short or char, to int.
   In addition, manifest constants symbols are replaced by their values.

   C++: this will automatically bash references to their target type.  */

tree
decay_conversion (exp)
     tree exp;
{
  register tree type = TREE_TYPE (exp);
  register enum tree_code code = TREE_CODE (type);

  if (code == OFFSET_TYPE /* || TREE_CODE (exp) == OFFSET_REF */ )
    {
      if (TREE_CODE (exp) == OFFSET_REF)
	return decay_conversion (resolve_offset_ref (exp));

      type = TREE_TYPE (type);
      code = TREE_CODE (type);
    }

  if (code == REFERENCE_TYPE)
    {
      exp = convert_from_reference (exp);
      type = TREE_TYPE (exp);
      code = TREE_CODE (type);
    }

  /* Constants can be used directly unless they're not loadable.  */
  if (TREE_CODE (exp) == CONST_DECL)
    exp = DECL_INITIAL (exp);
  /* Replace a nonvolatile const static variable with its value.  */
  else if (TREE_READONLY_DECL_P (exp))
    {
      exp = decl_constant_value (exp);
      type = TREE_TYPE (exp);
    }

  /* build_c_cast puts on a NOP_EXPR to make the result not an lvalue.
     Leave such NOP_EXPRs, since RHS is being used in non-lvalue context.  */

  if (code == VOID_TYPE)
    {
      error ("void value not ignored as it ought to be");
      return error_mark_node;
    }
  if (code == FUNCTION_TYPE)
    {
      return build_unary_op (ADDR_EXPR, exp, 0);
    }
  if (code == METHOD_TYPE)
    {
      if (TREE_CODE (exp) == OFFSET_REF)
	{
	  my_friendly_assert (TREE_CODE (TREE_OPERAND (exp, 1)) == FUNCTION_DECL,
			      308);
	  return build_unary_op (ADDR_EXPR, TREE_OPERAND (exp, 1), 0);
	}
      return build_unary_op (ADDR_EXPR, exp, 0);
    }
  if (code == ARRAY_TYPE)
    {
      register tree adr;
      tree restype;
      tree ptrtype;
      int constp, volatilep;

      if (TREE_CODE (exp) == INDIRECT_REF)
	{
	  /* Stripping away the INDIRECT_REF is not the right
	     thing to do for references...  */
	  tree inner = TREE_OPERAND (exp, 0);
	  if (TREE_CODE (TREE_TYPE (inner)) == REFERENCE_TYPE)
	    {
	      inner = build1 (CONVERT_EXPR,
			      build_pointer_type (TREE_TYPE (TREE_TYPE (inner))),
			      inner);
	      TREE_REFERENCE_EXPR (inner) = 1;
	    }
	  return convert (build_pointer_type (TREE_TYPE (type)), inner);
	}

      if (TREE_CODE (exp) == COMPOUND_EXPR)
	{
	  tree op1 = decay_conversion (TREE_OPERAND (exp, 1));
	  return build (COMPOUND_EXPR, TREE_TYPE (op1),
			TREE_OPERAND (exp, 0), op1);
	}

      if (!lvalue_p (exp)
	  && ! (TREE_CODE (exp) == CONSTRUCTOR && TREE_STATIC (exp)))
	{
	  error ("invalid use of non-lvalue array");
	  return error_mark_node;
	}

      constp = volatilep = 0;
      if (TREE_CODE_CLASS (TREE_CODE (exp)) == 'r'
	  || TREE_CODE_CLASS (TREE_CODE (exp)) == 'd')
	{
	  constp = TREE_READONLY (exp);
	  volatilep = TREE_THIS_VOLATILE (exp);
	}

      restype = TREE_TYPE (type);
      if (TYPE_READONLY (type) || TYPE_VOLATILE (type)
	  || constp || volatilep)
	restype = cp_build_type_variant (restype,
					TYPE_READONLY (type) || constp,
					TYPE_VOLATILE (type) || volatilep);
      ptrtype = build_pointer_type (restype);

      if (TREE_CODE (exp) == VAR_DECL)
	{
	  /* ??? This is not really quite correct
	     in that the type of the operand of ADDR_EXPR
	     is not the target type of the type of the ADDR_EXPR itself.
	     Question is, can this lossage be avoided?  */
	  adr = build1 (ADDR_EXPR, ptrtype, exp);
	  if (mark_addressable (exp) == 0)
	    return error_mark_node;
	  TREE_CONSTANT (adr) = staticp (exp);
	  TREE_SIDE_EFFECTS (adr) = 0;   /* Default would be, same as EXP.  */
	  return adr;
	}
      /* This way is better for a COMPONENT_REF since it can
	 simplify the offset for a component.  */
      adr = build_unary_op (ADDR_EXPR, exp, 1);
      return convert (ptrtype, adr);
    }

  return exp;
}

tree
default_conversion (exp)
     tree exp;
{
  tree type;
  enum tree_code code;

  exp = decay_conversion (exp);

  type = TREE_TYPE (exp);
  code = TREE_CODE (type);

  if (INTEGRAL_CODE_P (code))
    {
      tree t = type_promotes_to (type);
      if (t != type)
	return convert (t, exp);
    }
  if (flag_traditional
      && TYPE_MAIN_VARIANT (type) == float_type_node)
    return convert (double_type_node, exp);

  return exp;
}

tree
build_object_ref (datum, basetype, field)
     tree datum, basetype, field;
{
  tree dtype;
  if (datum == error_mark_node)
    return error_mark_node;

  dtype = TREE_TYPE (datum);
  if (TREE_CODE (dtype) == REFERENCE_TYPE)
    dtype = TREE_TYPE (dtype);
  if (! IS_AGGR_TYPE_CODE (TREE_CODE (dtype)))
    {
      cp_error ("request for member `%T::%D' in expression of non-aggregate type `%T'",
		basetype, field, dtype);
      return error_mark_node;
    }
  else if (IS_SIGNATURE (IDENTIFIER_TYPE_VALUE (basetype)))
    {
      warning ("signature name in scope resolution ignored");
      return build_component_ref (datum, field, NULL_TREE, 1);
    }
  else if (is_aggr_typedef (basetype, 1))
    {
      tree real_basetype = IDENTIFIER_TYPE_VALUE (basetype);
      tree binfo = binfo_or_else (real_basetype, TREE_TYPE (datum));
      if (binfo)
	return build_component_ref (build_scoped_ref (datum, basetype),
				    field, binfo, 1);
    }
  return error_mark_node;
}

/* Like `build_component_ref, but uses an already found field.
   Must compute access for C_C_D.  Otherwise, ok.  */
tree
build_component_ref_1 (datum, field, protect)
     tree datum, field;
     int protect;
{
  register tree basetype = TREE_TYPE (datum);
  register enum tree_code code = TREE_CODE (basetype);
  register tree ref;

  if (code == REFERENCE_TYPE)
    {
      datum = convert_from_reference (datum);
      basetype = TREE_TYPE (datum);
      code = TREE_CODE (basetype);
    }

  if (! IS_AGGR_TYPE_CODE (code))
    {
      if (code != ERROR_MARK)
	cp_error ("request for member `%D' in `%E', which is of non-aggregate type `%T'",
		  field, datum, basetype);
      return error_mark_node;
    }

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

  /* Look up component name in the structure type definition.  */

  if (field == error_mark_node)
    my_friendly_abort (115);

  if (TREE_STATIC (field))
    return field;

  if (datum == C_C_D)
    {
      enum access_type access
	= compute_access (TYPE_BINFO (current_class_type), field);

      if (access == access_private)
	{
	  cp_error ("field `%D' is private", field);
	  return error_mark_node;
	}
      else if (access == access_protected)
	{
	  cp_error ("field `%D' is protected", field);
	  return error_mark_node;
	}
    }

  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;
  if (DECL_MUTABLE_P (field))
    TREE_READONLY (ref) = 0;

  return ref;
}

/* Given a COND_EXPR in T, return it in a form that we can, for
   example, use as an lvalue.  This code used to be in unary_complex_lvalue,
   but we needed it to deal with `a = (d == c) ? b : c' expressions, where
   we're dealing with aggregates.  So, we now call this in unary_complex_lvalue,
   and in build_modify_expr.  The case (in particular) that led to this was
   with CODE == ADDR_EXPR, since it's not an lvalue when we'd get it there.  */
static tree
rationalize_conditional_expr (code, t)
     enum tree_code code;
     tree t;
{
  return
    build_conditional_expr (TREE_OPERAND (t, 0),
			    build_unary_op (code, TREE_OPERAND (t, 1), 0),
			    build_unary_op (code, TREE_OPERAND (t, 2), 0));
}

tree
build_component_ref (datum, component, basetype_path, protect)
     tree datum, component, basetype_path;
     int protect;
{
  register tree basetype = TREE_TYPE (datum);
  register enum tree_code code = TREE_CODE (basetype);
  register tree field = NULL;
  register tree ref;

  /* If DATUM is a COMPOUND_EXPR or COND_EXPR, move our reference inside it. */
  switch (TREE_CODE (datum))
    {
    case COMPOUND_EXPR:
      {
	tree value = build_component_ref (TREE_OPERAND (datum, 1), component,
					  basetype_path, protect);
	return build (COMPOUND_EXPR, TREE_TYPE (value),
		      TREE_OPERAND (datum, 0), value);
      }
    case COND_EXPR:
      return build_conditional_expr
	(TREE_OPERAND (datum, 0),
	 build_component_ref (TREE_OPERAND (datum, 1), component,
			      basetype_path, protect),
	 build_component_ref (TREE_OPERAND (datum, 2), component,
			      basetype_path, protect));
    }

  if (code == REFERENCE_TYPE)
    {
#if 0
      /* TREE_REFERENCE_EXPRs are not converted by `convert_from_reference'.
	 @@ Maybe that is not right.  */
      if (TREE_REFERENCE_EXPR (datum))
	datum = build1 (INDIRECT_REF, TREE_TYPE (basetype), datum);
      else
#endif
	datum = convert_from_reference (datum);
      basetype = TREE_TYPE (datum);
      code = TREE_CODE (basetype);
    }

  /* First, see if there is a field or component with name COMPONENT. */
  if (TREE_CODE (component) == TREE_LIST)
    {
      my_friendly_assert (!(TREE_CHAIN (component) == NULL_TREE
		&& DECL_CHAIN (TREE_VALUE (component)) == NULL_TREE), 309);
      return build (COMPONENT_REF, TREE_TYPE (component), datum, component);
    }
#if 0
  if (TREE_CODE (component) == TYPE_EXPR)
    return build_component_type_expr (datum, component, NULL_TREE, protect);
#endif

  if (! IS_AGGR_TYPE_CODE (code))
    {
      if (code != ERROR_MARK)
	cp_error ("request for member `%D' in `%E', which is of non-aggregate type `%T'",
		  component, datum, basetype);
      return error_mark_node;
    }

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

  if (TREE_CODE (component) == BIT_NOT_EXPR)
    {
      if (TYPE_IDENTIFIER (basetype) != TREE_OPERAND (component, 0))
	{
	  cp_error ("destructor specifier `%T::~%T' must have matching names",
		    basetype, TREE_OPERAND (component, 0));
	  return error_mark_node;
	}
      if (! TYPE_HAS_DESTRUCTOR (basetype))
	{
	  cp_error ("type `%T' has no destructor", basetype);
	  return error_mark_node;
	}
      return TREE_VEC_ELT (CLASSTYPE_METHOD_VEC (basetype), 0);
    }

  /* Look up component name in the structure type definition.  */
  if (CLASSTYPE_VFIELD (basetype)
      && DECL_NAME (CLASSTYPE_VFIELD (basetype)) == component)
    /* Special-case this because if we use normal lookups in an ambiguous
       hierarchy, the compiler will abort (because vptr lookups are
       not supposed to be ambiguous.  */
    field = CLASSTYPE_VFIELD (basetype);
  else
    {
      if (basetype_path == NULL_TREE)
	basetype_path = TYPE_BINFO (basetype);
      field = lookup_field (basetype_path, component,
			    protect && ! VFIELD_NAME_P (component), 0);
      if (field == error_mark_node)
	return error_mark_node;

      if (field == NULL_TREE)
	{
	  /* Not found as a data field, look for it as a method.  If found,
	     then if this is the only possible one, return it, else
	     report ambiguity error.  */
	  tree fndecls = lookup_fnfields (basetype_path, component, 1);
	  if (fndecls == error_mark_node)
	    return error_mark_node;
	  if (fndecls)
	    {
	      if (TREE_CHAIN (fndecls) == NULL_TREE
		  && DECL_CHAIN (TREE_VALUE (fndecls)) == NULL_TREE)
		{
		  enum access_type access;
		  tree fndecl;

		  /* Unique, so use this one now.  */
		  basetype = TREE_PURPOSE (fndecls);
		  fndecl = TREE_VALUE (fndecls);
		  access = compute_access (TREE_PURPOSE (fndecls), fndecl);
		  if (access == access_public)
		    {
		      if (DECL_VINDEX (fndecl)
			  && ! resolves_to_fixed_type_p (datum, 0))
			{
			  tree addr = build_unary_op (ADDR_EXPR, datum, 0);
			  addr = convert_pointer_to (DECL_CONTEXT (fndecl), addr);
			  datum = build_indirect_ref (addr, NULL_PTR);
			  my_friendly_assert (datum != error_mark_node, 310);
			  fndecl = build_vfn_ref (&addr, datum, DECL_VINDEX (fndecl));
			}
		      assemble_external (fndecl);
		      return fndecl;
		    }
		  if (access == access_protected)
		    cp_error ("member function `%D' is protected", fndecl);
		  else
		    cp_error ("member function `%D' is private", fndecl);
		  return error_mark_node;
		}
	      else
		{
		  /* Just act like build_offset_ref, since the object does
                     not matter unless we're actually calling the function.  */
		  tree t;

		  for (t = TREE_VALUE (fndecls); t; t = DECL_CHAIN (t))
		    assemble_external (t);

		  t = build_tree_list (error_mark_node, fndecls);
		  TREE_TYPE (t) = build_offset_type (basetype,
						     unknown_type_node);
		  return t;
		}
	    }