typeck.c

gcc-2.95.3 Linux下最常用的C编译器

/* Build expressions with type checking for C++ compiler.
   Copyright (C) 1987, 88, 89, 92-98, 1999 Free Software Foundation, Inc.
   Hacked by Michael Tiemann ([e-mail])

This file is part of GNU CC.

GNU CC is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2, or (at your option)
any later version.

GNU CC is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with GNU CC; see the file COPYING.  If not, write to
the Free Software Foundation, 59 Temple Place - Suite 330,
Boston, MA 02111-1307, USA.  */


/* This file is part of the C++ front end.
   It contains routines to build C++ expressions given their operands,
   including computing the types of the result, C and C++ specific error
   checks, and some optimization.

   There are also routines to build RETURN_STMT nodes and CASE_STMT nodes,
   and to process initializations in declarations (since they work
   like a strange sort of assignment).  */

#include "config.h"
#include "system.h"
#include "tree.h"
#include "rtl.h"
#include "cp-tree.h"
#include "flags.h"
#include "output.h"
#include "expr.h"
#include "toplev.h"

static tree convert_for_assignment PROTO((tree, tree, const char *, tree,
					  int));
static tree pointer_int_sum PROTO((enum tree_code, tree, tree));
static tree rationalize_conditional_expr PROTO((enum tree_code, tree));
static int comp_target_parms PROTO((tree, tree, int));
static int comp_ptr_ttypes_real PROTO((tree, tree, int));
static int comp_ptr_ttypes_const PROTO((tree, tree));
static int comp_ptr_ttypes_reinterpret PROTO((tree, tree));
static int comp_array_types PROTO((int (*) (tree, tree, int), tree,
				   tree, int));
static tree common_base_type PROTO((tree, tree));
#if 0
static tree convert_sequence PROTO((tree, tree));
#endif
static tree lookup_anon_field PROTO((tree, tree));
static tree pointer_diff PROTO((tree, tree, tree));
static tree build_component_addr PROTO((tree, tree));
static tree qualify_type PROTO((tree, tree));
static tree get_delta_difference PROTO((tree, tree, int));
static int comp_cv_target_types PROTO((tree, tree, int));

/* Return the target type of TYPE, which meas return T for:
   T*, T&, T[], T (...), and otherwise, just T.  */

tree
target_type (type)
     tree type;
{
  if (TREE_CODE (type) == REFERENCE_TYPE)
    type = TREE_TYPE (type);
  while (TREE_CODE (type) == POINTER_TYPE
	 || TREE_CODE (type) == ARRAY_TYPE
	 || TREE_CODE (type) == FUNCTION_TYPE
	 || TREE_CODE (type) == METHOD_TYPE
	 || TREE_CODE (type) == OFFSET_TYPE)
    type = TREE_TYPE (type);
  return type;
}

/* Do `exp = require_complete_type (exp);' to make sure exp
   does not have an incomplete type.  (That includes void types.)
   Returns the error_mark_node if the VALUE does not have
   complete type when this function returns.  */

tree
require_complete_type (value)
     tree value;
{
  tree type;

  if (processing_template_decl || value == error_mark_node)
    return value;

  if (TREE_CODE (value) == OVERLOAD)
    type = unknown_type_node;
  else
    type = TREE_TYPE (value);

  /* First, detect a valid value with a complete type.  */
  if (TYPE_SIZE (type) != 0
      && TYPE_SIZE (type) != size_zero_node
      && ! (TYPE_LANG_SPECIFIC (type)
	    && (IS_SIGNATURE_POINTER (type) || IS_SIGNATURE_REFERENCE (type))
	    && TYPE_SIZE (SIGNATURE_TYPE (type)) == 0))
    return value;

  /* If we see X::Y, we build an OFFSET_TYPE which has
     not been laid out.  Try to avoid an error by interpreting
     it as this->X::Y, if reasonable.  */
  if (TREE_CODE (value) == OFFSET_REF
      && current_class_ref != 0
      && TREE_OPERAND (value, 0) == current_class_ref)
    {
      tree base, member = TREE_OPERAND (value, 1);
      tree basetype = TYPE_OFFSET_BASETYPE (type);
      my_friendly_assert (TREE_CODE (member) == FIELD_DECL, 305);
      base = convert_pointer_to (basetype, current_class_ptr);
      value = build (COMPONENT_REF, TREE_TYPE (member),
		     build_indirect_ref (base, NULL_PTR), member);
      return require_complete_type (value);
    }

  if (complete_type_or_else (type, value))
    return value;
  else
    return error_mark_node;
}

/* Makes sure EXPR is a complete type when used in a void context, like a
   whole expression, or lhs of a comma operator. Issue a diagnostic and
   return error_mark_node on failure. This is a little tricky, because some
   valid void types look stunningly similar to invalid void types. We err on
   the side of caution */

tree
require_complete_type_in_void (expr)
     tree expr;
{
  switch (TREE_CODE (expr))
    {
    case COND_EXPR:
      {
        tree op;
        
        op = TREE_OPERAND (expr,2);
        op = require_complete_type_in_void (op);
        TREE_OPERAND (expr,2) = op;
        if (op == error_mark_node)
          {
            expr = op;
            break;
          }
        
        /* fallthrough */
      }
    
    case COMPOUND_EXPR:
      {
        tree op;
        
        op = TREE_OPERAND (expr,1);
        op = require_complete_type_in_void (op);
        TREE_OPERAND (expr,1) = op;
        if (op == error_mark_node)
          {
            expr = op;
            break;
          }
        
        break;
      }
    
    case NON_LVALUE_EXPR:
    case NOP_EXPR:
      {
        tree op;
        
        op = TREE_OPERAND (expr,0);
        op = require_complete_type_in_void (op);
        TREE_OPERAND (expr,0) = op;
        if (op == error_mark_node)
          {
            expr = op;
            break;
          }
        break;
      }
    
    case CALL_EXPR:   /* function call return can be ignored */
    case RTL_EXPR:    /* RTL nodes have no value */
    case DELETE_EXPR: /* delete expressions have no type */
    case VEC_DELETE_EXPR:
    case INTEGER_CST: /* used for null pointer */
    case EXIT_EXPR:   /* have no return */
    case LOOP_EXPR:   /* have no return */
    case BIND_EXPR:   /* have no return */
    case THROW_EXPR:  /* have no return */
    case MODIFY_EXPR: /* sometimes this has a void type, but that's ok */
    case CONVERT_EXPR:  /* sometimes has a void type */
      break;
    
    case INDIRECT_REF:
      {
        tree op = TREE_OPERAND (expr,0);
        
        /* Calling a function returning a reference has an implicit
           dereference applied. We don't want to make that an error. */
        if (TREE_CODE (op) == CALL_EXPR
            && TREE_CODE (TREE_TYPE (op)) == REFERENCE_TYPE)
          break;
        /* else fallthrough */
      }
    
    default:
      expr = require_complete_type (expr);
      break;
    }

  return expr;
}

/* Try to complete TYPE, if it is incomplete.  For example, if TYPE is
   a template instantiation, do the instantiation.  Returns TYPE,
   whether or not it could be completed, unless something goes
   horribly wrong, in which case the error_mark_node is returned.  */

tree
complete_type (type)
     tree type;
{
  if (type == NULL_TREE)
    /* Rather than crash, we return something sure to cause an error
       at some point.  */
    return error_mark_node;

  if (type == error_mark_node || TYPE_SIZE (type) != NULL_TREE)
    ;
  else if (TREE_CODE (type) == ARRAY_TYPE && TYPE_DOMAIN (type))
    {
      tree t = complete_type (TREE_TYPE (type));
      if (TYPE_SIZE (t) != NULL_TREE && ! processing_template_decl)
	layout_type (type);
      TYPE_NEEDS_CONSTRUCTING (type)
	= TYPE_NEEDS_CONSTRUCTING (TYPE_MAIN_VARIANT (t));
      TYPE_NEEDS_DESTRUCTOR (type)
	= TYPE_NEEDS_DESTRUCTOR (TYPE_MAIN_VARIANT (t));
    }
  else if (CLASS_TYPE_P (type) && CLASSTYPE_TEMPLATE_INSTANTIATION (type))
    instantiate_class_template (TYPE_MAIN_VARIANT (type));

  return type;
}

/* Like complete_type, but issue an error if the TYPE cannot be
   completed.  VALUE is used for informative diagnostics.
   Returns NULL_TREE if the type cannot be made complete.  */

tree
complete_type_or_else (type, value)
     tree type;
     tree value;
{
  type = complete_type (type);
  if (type == error_mark_node)
    /* We already issued an error.  */
    return NULL_TREE;
  else if (!TYPE_SIZE (type) || TYPE_SIZE (type) == size_zero_node)
    {
      incomplete_type_error (value, type);
      return NULL_TREE;
    }
  else
    return type;
}

/* Return truthvalue of whether type of EXP is instantiated.  */

int
type_unknown_p (exp)
     tree exp;
{
  return (TREE_CODE (exp) == OVERLOAD
          || TREE_CODE (exp) == TREE_LIST
	  || TREE_TYPE (exp) == unknown_type_node
	  || (TREE_CODE (TREE_TYPE (exp)) == OFFSET_TYPE
	      && TREE_TYPE (TREE_TYPE (exp)) == unknown_type_node));
}

/* Return truthvalue of whether T is function (or pfn) type.  */

int
fntype_p (t)
     tree t;
{
  return (TREE_CODE (t) == FUNCTION_TYPE || TREE_CODE (t) == METHOD_TYPE
	  || (TREE_CODE (t) == POINTER_TYPE
	      && (TREE_CODE (TREE_TYPE (t)) == FUNCTION_TYPE
		  || TREE_CODE (TREE_TYPE (t)) == METHOD_TYPE)));
}

/* Return a variant of TYPE which has all the type qualifiers of LIKE
   as well as those of TYPE.  */

static tree
qualify_type (type, like)
     tree type, like;
{
  /* @@ Must do member pointers here.  */
  return cp_build_qualified_type (type, (CP_TYPE_QUALS (type) 
					 | CP_TYPE_QUALS (like)));
}

/* Return the common type of two parameter lists.
   We assume that comptypes has already been done and returned 1;
   if that isn't so, this may crash.

   As an optimization, free the space we allocate if the parameter
   lists are already common.  */

tree
commonparms (p1, p2)
     tree p1, p2;
{
  tree oldargs = p1, newargs, n;
  int i, len;
  int any_change = 0;
  char *first_obj = (char *) oballoc (0);

  len = list_length (p1);
  newargs = tree_last (p1);

  if (newargs == void_list_node)
    i = 1;
  else
    {
      i = 0;
      newargs = 0;
    }

  for (; i < len; i++)
    newargs = tree_cons (NULL_TREE, NULL_TREE, newargs);

  n = newargs;

  for (i = 0; p1;
       p1 = TREE_CHAIN (p1), p2 = TREE_CHAIN (p2), n = TREE_CHAIN (n), i++)
    {
      if (TREE_PURPOSE (p1) && !TREE_PURPOSE (p2))
	{
	  TREE_PURPOSE (n) = TREE_PURPOSE (p1);
	  any_change = 1;
	}
      else if (! TREE_PURPOSE (p1))
	{
	  if (TREE_PURPOSE (p2))
	    {
	      TREE_PURPOSE (n) = TREE_PURPOSE (p2);
	      any_change = 1;
	    }
	}
      else
	{
	  if (1 != simple_cst_equal (TREE_PURPOSE (p1), TREE_PURPOSE (p2)))
	    any_change = 1;
	  TREE_PURPOSE (n) = TREE_PURPOSE (p2);
	}
      if (TREE_VALUE (p1) != TREE_VALUE (p2))
	{
	  any_change = 1;
	  TREE_VALUE (n) = common_type (TREE_VALUE (p1), TREE_VALUE (p2));
	}
      else
	TREE_VALUE (n) = TREE_VALUE (p1);
    }
  if (! any_change)
    {
      obfree (first_obj);
      return oldargs;
    }

  return newargs;
}

/* Given a type, perhaps copied for a typedef,
   find the "original" version of it.  */
tree
original_type (t)
     tree t;
{
  while (TYPE_NAME (t) != NULL_TREE)
    {
      tree x = TYPE_NAME (t);
      if (TREE_CODE (x) != TYPE_DECL)
	break;
      x = DECL_ORIGINAL_TYPE (x);
      if (x == NULL_TREE)
	break;
      t = x;
    }
  return t;
}

/* Return the common type of two types.
   We assume that comptypes has already been done and returned 1;
   if that isn't so, this may crash.

   This is the type for the result of most arithmetic operations
   if the operands have the given two types.

   We do not deal with enumeral types here because they have already been
   converted to integer types.  */

tree
common_type (t1, t2)
     tree t1, t2;
{
  register enum tree_code code1;
  register enum tree_code code2;
  tree attributes;

  /* Save time if the two types are the same.  */
  if (t1 == t2)
    return t1;
  t1 = original_type (t1);
  t2 = original_type (t2);
  if (t1 == t2)
    return t1;

  /* If one type is nonsense, use the other.  */
  if (t1 == error_mark_node)
    return t2;
  if (t2 == error_mark_node)
    return t1;

  /* Merge the attributes.  */
  attributes = merge_machine_type_attributes (t1, t2);

  { register tree a1, a2;
    a1 = TYPE_ATTRIBUTES (t1);
    a2 = TYPE_ATTRIBUTES (t2);

    /* Either one unset?  Take the set one.  */

    if (!(attributes = a1))
       attributes = a2;

    /* One that completely contains the other?  Take it.  */

    else if (a2 && !attribute_list_contained (a1, a2))
      {
	if (attribute_list_contained (a2, a1))
	  attributes = a2;
	else
	  {
	    /* Pick the longest list, and hang on the other list.  */
	    /* ??? For the moment we punt on the issue of attrs with args.  */