call.c

gcc-2.95.3 Linux下最常用的C编译器

   purposes of reference binding.  For lvalue binding, either pass a
   reference type to FROM or an lvalue expression to EXPR.

   Currently does not distinguish in the generated trees between binding to
   an lvalue and a temporary.  Should it?  */

static tree
reference_binding (rto, rfrom, expr, flags)
     tree rto, rfrom, expr;
     int flags;
{
  tree conv;
  int lvalue = 1;
  tree to = TREE_TYPE (rto);
  tree from = rfrom;
  int related;

  if (TREE_CODE (to) == FUNCTION_TYPE && expr && type_unknown_p (expr))
    {
      expr = instantiate_type (to, expr, 0);
      if (expr == error_mark_node)
	return NULL_TREE;
      from = TREE_TYPE (expr);
    }

  if (TREE_CODE (from) == REFERENCE_TYPE)
    from = TREE_TYPE (from);
  else if (! expr || ! real_lvalue_p (expr))
    lvalue = 0;

  related = (same_type_p (TYPE_MAIN_VARIANT (to),
			  TYPE_MAIN_VARIANT (from))
	     || (IS_AGGR_TYPE (to) && IS_AGGR_TYPE (from)
		 && DERIVED_FROM_P (to, from)));

  if (lvalue && related && at_least_as_qualified_p (to, from))
    {
      conv = build1 (IDENTITY_CONV, from, expr);

      if (same_type_p (TYPE_MAIN_VARIANT (to),
		       TYPE_MAIN_VARIANT (from)))
	conv = build_conv (REF_BIND, rto, conv);
      else
	{
	  conv = build_conv (REF_BIND, rto, conv);
	  ICS_STD_RANK (conv) = STD_RANK;
	}
    }
  else
    conv = NULL_TREE;

  if (! conv)
    {
      conv = standard_conversion (to, rfrom, expr);
      if (conv)
	{
	  conv = build_conv (REF_BIND, rto, conv);

	  /* Bind directly to a base subobject of a class rvalue.  Do it
             after building the conversion for proper handling of ICS_RANK.  */
	  if (TREE_CODE (TREE_OPERAND (conv, 0)) == BASE_CONV)
	    TREE_OPERAND (conv, 0) = TREE_OPERAND (TREE_OPERAND (conv, 0), 0);
	}
      if (conv
	  && ((! (CP_TYPE_CONST_NON_VOLATILE_P (to)
		  && (flags & LOOKUP_NO_TEMP_BIND) == 0))
	      /* If T1 is reference-related to T2, cv1 must be the same
		 cv-qualification as, or greater cv-qualification than,
		 cv2; otherwise, the program is ill-formed.  */
	      || (related && !at_least_as_qualified_p (to, from))))
	ICS_BAD_FLAG (conv) = 1;
    }

  return conv;
}

/* Returns the implicit conversion sequence (see [over.ics]) from type FROM
   to type TO.  The optional expression EXPR may affect the conversion.
   FLAGS are the usual overloading flags.  Only LOOKUP_NO_CONVERSION is
   significant.  */

static tree
implicit_conversion (to, from, expr, flags)
     tree to, from, expr;
     int flags;
{
  tree conv;
  struct z_candidate *cand;

  if (TREE_CODE (to) == REFERENCE_TYPE)
    conv = reference_binding (to, from, expr, flags);
  else
    conv = standard_conversion (to, from, expr);

  if (conv)
    ;
  else if (expr != NULL_TREE
	   && (IS_AGGR_TYPE (non_reference (from))
	       || IS_AGGR_TYPE (non_reference (to)))
	   && (flags & LOOKUP_NO_CONVERSION) == 0)
    {
      cand = build_user_type_conversion_1
	(to, expr, LOOKUP_ONLYCONVERTING);
      if (cand)
	conv = cand->second_conv;
      if ((! conv || ICS_BAD_FLAG (conv))
	  && TREE_CODE (to) == REFERENCE_TYPE
	  && (flags & LOOKUP_NO_TEMP_BIND) == 0)
	{
	  cand = build_user_type_conversion_1
	    (TYPE_MAIN_VARIANT (TREE_TYPE (to)), expr, LOOKUP_ONLYCONVERTING);
	  if (cand)
	    {
	      if (!CP_TYPE_CONST_NON_VOLATILE_P (TREE_TYPE (to)))
		ICS_BAD_FLAG (cand->second_conv) = 1;
	      if (!conv || (ICS_BAD_FLAG (conv)
			    > ICS_BAD_FLAG (cand->second_conv)))
		conv = build_conv (REF_BIND, to, cand->second_conv);
	    }
	}
    }

  return conv;
}

/* Add a new entry to the list of candidates.  Used by the add_*_candidate
   functions.  */

static struct z_candidate *
add_candidate (candidates, fn, convs, viable)
     struct z_candidate *candidates;
     tree fn, convs;
     int viable;
{
  struct z_candidate *cand
    = (struct z_candidate *) scratchalloc (sizeof (struct z_candidate));

  cand->fn = fn;
  cand->convs = convs;
  cand->second_conv = NULL_TREE;
  cand->viable = viable;
  cand->basetype_path = NULL_TREE;
  cand->template = NULL_TREE;
  cand->warnings = NULL_TREE;
  cand->next = candidates;

  return cand;
}

/* Create an overload candidate for the function or method FN called with
   the argument list ARGLIST and add it to CANDIDATES.  FLAGS is passed on
   to implicit_conversion.  */

static struct z_candidate *
add_function_candidate (candidates, fn, arglist, flags)
     struct z_candidate *candidates;
     tree fn, arglist;
     int flags;
{
  tree parmlist = TYPE_ARG_TYPES (TREE_TYPE (fn));
  int i, len;
  tree convs;
  tree parmnode, argnode;
  int viable = 1;

  /* The `this', `in_chrg', and `vlist' arguments to constructors are
     not considered in overload resolution.  */
  if (DECL_CONSTRUCTOR_P (fn))
    {
      parmlist = TREE_CHAIN (parmlist);
      arglist = TREE_CHAIN (arglist);
      if (TYPE_USES_VIRTUAL_BASECLASSES (DECL_CONTEXT (fn)))
	{
	  parmlist = TREE_CHAIN (parmlist);
	  arglist = TREE_CHAIN (arglist);
	}
      if ((flags & LOOKUP_HAS_VLIST)
	  && DECL_CONSTRUCTOR_FOR_PVBASE_P (fn))
	{
	  parmlist = TREE_CHAIN (parmlist);
	  arglist = TREE_CHAIN (arglist);
	}
      else if (!(flags & LOOKUP_HAS_VLIST)
	       && !DECL_CONSTRUCTOR_FOR_PVBASE_P (fn))
	/* Ok */;
      else
	{
	  /* The ctor expects a vlist and the arguments don't have
	     one, or vice versa, so fn is not even a candidate, since
	     the corresponding ctor would be the candidate.  */
	  return candidates;
	}
    }

  len = list_length (arglist);
  convs = make_scratch_vec (len);

  /* 13.3.2 - Viable functions [over.match.viable]
     First, to be a viable function, a candidate function shall have enough
     parameters to agree in number with the arguments in the list.

     We need to check this first; otherwise, checking the ICSes might cause
     us to produce an ill-formed template instantiation.  */

  parmnode = parmlist;
  for (i = 0; i < len; ++i)
    {
      if (parmnode == NULL_TREE || parmnode == void_list_node)
	break;
      parmnode = TREE_CHAIN (parmnode);
    }

  if (i < len && parmnode)
    viable = 0;

  /* Make sure there are default args for the rest of the parms.  */
  else for (; parmnode && parmnode != void_list_node;
	    parmnode = TREE_CHAIN (parmnode))
    if (! TREE_PURPOSE (parmnode))
      {
	viable = 0;
	break;
      }

  if (! viable)
    goto out;

  /* Second, for F to be a viable function, there shall exist for each
     argument an implicit conversion sequence that converts that argument
     to the corresponding parameter of F.  */

  parmnode = parmlist;
  argnode = arglist;

  for (i = 0; i < len; ++i)
    {
      tree arg = TREE_VALUE (argnode);
      tree argtype = lvalue_type (arg);
      tree t;

      if (parmnode == void_list_node)
	break;

      if (parmnode)
	{
	  tree parmtype = TREE_VALUE (parmnode);

	  /* [over.match.funcs] For conversion functions, the function is
	     considered to be a member of the class of the implicit object
	     argument for the purpose of defining the type of the implicit
	     object parameter.

	     Since build_over_call ignores the ICS for the `this' parameter,
	     we can just change the parm type.  */
	  if (DECL_CONV_FN_P (fn) && i == 0)
	    {
	      parmtype
		= build_qualified_type (TREE_TYPE (argtype),
					TYPE_QUALS (TREE_TYPE (parmtype)));
	      parmtype = build_pointer_type (parmtype);
	    }

	  t = implicit_conversion (parmtype, argtype, arg, flags);
	}
      else
	{
	  t = build1 (IDENTITY_CONV, argtype, arg);
	  ICS_ELLIPSIS_FLAG (t) = 1;
	}

      if (i == 0 && t && TREE_CODE (TREE_TYPE (fn)) == METHOD_TYPE
	  && ! DECL_CONSTRUCTOR_P (fn))
	ICS_THIS_FLAG (t) = 1;

      TREE_VEC_ELT (convs, i) = t;
      if (! t)
	{
	  viable = 0;
	  break;
	}

      if (ICS_BAD_FLAG (t))
	viable = -1;

      if (parmnode)
	parmnode = TREE_CHAIN (parmnode);
      argnode = TREE_CHAIN (argnode);
    }

 out:
  return add_candidate (candidates, fn, convs, viable);
}

/* Create an overload candidate for the conversion function FN which will
   be invoked for expression OBJ, producing a pointer-to-function which
   will in turn be called with the argument list ARGLIST, and add it to
   CANDIDATES.  FLAGS is passed on to implicit_conversion.

   Actually, we don't really care about FN; we care about the type it
   converts to.  There may be multiple conversion functions that will
   convert to that type, and we rely on build_user_type_conversion_1 to
   choose the best one; so when we create our candidate, we record the type
   instead of the function.  */

static struct z_candidate *
add_conv_candidate (candidates, fn, obj, arglist)
     struct z_candidate *candidates;
     tree fn, obj, arglist;
{
  tree totype = TREE_TYPE (TREE_TYPE (fn));
  tree parmlist = TYPE_ARG_TYPES (TREE_TYPE (totype));
  int i, len = list_length (arglist) + 1;
  tree convs = make_scratch_vec (len);
  tree parmnode = parmlist;
  tree argnode = arglist;
  int viable = 1;
  int flags = LOOKUP_NORMAL;

  /* Don't bother looking up the same type twice.  */
  if (candidates && candidates->fn == totype)
    return candidates;

  for (i = 0; i < len; ++i)
    {
      tree arg = i == 0 ? obj : TREE_VALUE (argnode);
      tree argtype = lvalue_type (arg);
      tree t;

      if (i == 0)
	t = implicit_conversion (totype, argtype, arg, flags);
      else if (parmnode == void_list_node)
	break;
      else if (parmnode)
	t = implicit_conversion (TREE_VALUE (parmnode), argtype, arg, flags);
      else
	{
	  t = build1 (IDENTITY_CONV, argtype, arg);
	  ICS_ELLIPSIS_FLAG (t) = 1;
	}

      TREE_VEC_ELT (convs, i) = t;
      if (! t)
	break;

      if (ICS_BAD_FLAG (t))
	viable = -1;

      if (i == 0)
	continue;

      if (parmnode)
	parmnode = TREE_CHAIN (parmnode);
      argnode = TREE_CHAIN (argnode);
    }

  if (i < len)
    viable = 0;

  for (; parmnode && parmnode != void_list_node;
       parmnode = TREE_CHAIN (parmnode))
    if (! TREE_PURPOSE (parmnode))
      {
	viable = 0;
	break;
      }

  return add_candidate (candidates, totype, convs, viable);
}

static struct z_candidate *
build_builtin_candidate (candidates, fnname, type1, type2,
			 args, argtypes, flags)
     struct z_candidate *candidates;
     tree fnname, type1, type2, *args, *argtypes;
     int flags;

{
  tree t, convs;
  int viable = 1, i;
  tree types[2];

  types[0] = type1;
  types[1] = type2;

  convs = make_scratch_vec (args[2] ? 3 : (args[1] ? 2 : 1));

  for (i = 0; i < 2; ++i)
    {
      if (! args[i])
	break;

      t = implicit_conversion (types[i], argtypes[i], args[i], flags);
      if (! t)
	{
	  viable = 0;
	  /* We need something for printing the candidate.  */
	  t = build1 (IDENTITY_CONV, types[i], NULL_TREE);
	}
      else if (ICS_BAD_FLAG (t))
	viable = 0;
      TREE_VEC_ELT (convs, i) = t;
    }

  /* For COND_EXPR we rearranged the arguments; undo that now.  */
  if (args[2])
    {
      TREE_VEC_ELT (convs, 2) = TREE_VEC_ELT (convs, 1);
      TREE_VEC_ELT (convs, 1) = TREE_VEC_ELT (convs, 0);
      t = implicit_conversion (boolean_type_node, argtypes[2], args[2], flags);
      if (t)
	TREE_VEC_ELT (convs, 0) = t;
      else
	viable = 0;
    }      

  return add_candidate (candidates, fnname, convs, viable);
}

static int
is_complete (t)
     tree t;
{
  return TYPE_SIZE (complete_type (t)) != NULL_TREE;
}

/* Create any builtin operator overload candidates for the operator in
   question given the converted operand types TYPE1 and TYPE2.  The other
   args are passed through from add_builtin_candidates to
   build_builtin_candidate.  */

static struct z_candidate *
add_builtin_candidate (candidates, code, code2, fnname, type1, type2,
		       args, argtypes, flags)
     struct z_candidate *candidates;
     enum tree_code code, code2;
     tree fnname, type1, type2, *args, *argtypes;
     int flags;
{
  switch (code)
    {
    case POSTINCREMENT_EXPR:
    case POSTDECREMENT_EXPR:
      args[1] = integer_zero_node;
      type2 = integer_type_node;
      break;
    default:
      break;
    }

  switch (code)
    {