cvt.c

gcc-2.95.3 Linux下最常用的C编译器

    }
  else
    rval
      = convert_to_pointer_force (build_pointer_type (target_type), rval);
  rval = build1 (NOP_EXPR, type, rval);
  TREE_CONSTANT (rval) = TREE_CONSTANT (TREE_OPERAND (rval, 0));
  return rval;
}

/* For C++: Only need to do one-level references, but cannot
   get tripped up on signed/unsigned differences.

   DECL is either NULL_TREE or the _DECL node for a reference that is being
   initialized.  It can be error_mark_node if we don't know the _DECL but
   we know it's an initialization.  */

tree
convert_to_reference (reftype, expr, convtype, flags, decl)
     tree reftype, expr;
     int convtype, flags;
     tree decl;
{
  register tree type = TYPE_MAIN_VARIANT (TREE_TYPE (reftype));
  register tree intype = TREE_TYPE (expr);
  tree rval = NULL_TREE;
  tree rval_as_conversion = NULL_TREE;
  int i;

  if (TREE_CODE (type) == FUNCTION_TYPE && intype == unknown_type_node)
    {
      expr = instantiate_type (type, expr, 
			       (flags & LOOKUP_COMPLAIN) != 0);
      if (expr == error_mark_node)
	return error_mark_node;

      intype = TREE_TYPE (expr);
    }

  if (TREE_CODE (intype) == REFERENCE_TYPE)
    my_friendly_abort (364);

  intype = TYPE_MAIN_VARIANT (intype);

  i = comp_target_types (type, intype, 0);

  if (i <= 0 && (convtype & CONV_IMPLICIT) && IS_AGGR_TYPE (intype)
      && ! (flags & LOOKUP_NO_CONVERSION))
    {
      /* Look for a user-defined conversion to lvalue that we can use.  */

      rval_as_conversion
	= build_type_conversion (reftype, expr, 1);

      if (rval_as_conversion && rval_as_conversion != error_mark_node
	  && real_lvalue_p (rval_as_conversion))
	{
	  expr = rval_as_conversion;
	  rval_as_conversion = NULL_TREE;
	  intype = type;
	  i = 1;
	}
    }

  if (((convtype & CONV_STATIC) && i == -1)
      || ((convtype & CONV_IMPLICIT) && i == 1))
    {
      if (flags & LOOKUP_COMPLAIN)
	{
	  tree ttl = TREE_TYPE (reftype);
	  tree ttr = lvalue_type (expr);

	  /* [dcl.init.ref] says that if an rvalue is used to
	     initialize a reference, then the reference must be to a
	     non-volatile const type.  */
	  if (! real_lvalue_p (expr)
	      && !CP_TYPE_CONST_NON_VOLATILE_P (ttl))
	    {
	      const char *msg;

	      if (CP_TYPE_VOLATILE_P (ttl) && decl)
		msg = "initialization of volatile reference type `%#T'";
	      else if (CP_TYPE_VOLATILE_P (ttl))
		msg = "conversion to volatile reference type `%#T'";
	      else if (decl)
		msg = "initialization of non-const reference type `%#T'";
	      else
		msg = "conversion to non-const reference type `%#T'";

	      cp_pedwarn (msg, reftype);
	      cp_pedwarn ("from rvalue of type `%T'", intype);
	    }
	  else if (! (convtype & CONV_CONST)
		   && !at_least_as_qualified_p (ttl, ttr))
	    cp_pedwarn ("conversion from `%T' to `%T' discards qualifiers",
			ttr, reftype);
	}

      return build_up_reference (reftype, expr, flags);
    }
  else if ((convtype & CONV_REINTERPRET) && lvalue_p (expr))
    {
      /* When casting an lvalue to a reference type, just convert into
	 a pointer to the new type and deference it.  This is allowed
	 by San Diego WP section 5.2.9 paragraph 12, though perhaps it
	 should be done directly (jason).  (int &)ri ---> *(int*)&ri */

      /* B* bp; A& ar = (A&)bp; is valid, but it's probably not what they
         meant.  */
      if (TREE_CODE (intype) == POINTER_TYPE
	  && (comptypes (TREE_TYPE (intype), type, 
			 COMPARE_BASE | COMPARE_RELAXED )))
	cp_warning ("casting `%T' to `%T' does not dereference pointer",
		    intype, reftype);
	  
      rval = build_unary_op (ADDR_EXPR, expr, 0);
      if (rval != error_mark_node)
	rval = convert_force (build_pointer_type (TREE_TYPE (reftype)),
			      rval, 0);
      if (rval != error_mark_node)
	rval = build1 (NOP_EXPR, reftype, rval);
    }
  else
    {
      rval = convert_for_initialization (NULL_TREE, type, expr, flags,
					 "converting", 0, 0);
      if (rval == NULL_TREE || rval == error_mark_node)
	return rval;
      rval = build_up_reference (reftype, rval, flags);

      if (rval && ! CP_TYPE_CONST_P (TREE_TYPE (reftype)))
	cp_pedwarn ("initializing non-const `%T' with `%T' will use a temporary",
		    reftype, intype);
    }

  if (rval)
    {
      /* If we found a way to convert earlier, then use it.  */
      return rval;
    }

  my_friendly_assert (TREE_CODE (intype) != OFFSET_TYPE, 189);

  if (flags & LOOKUP_COMPLAIN)
    cp_error ("cannot convert type `%T' to type `%T'", intype, reftype);

  if (flags & LOOKUP_SPECULATIVELY)
    return NULL_TREE;

  return error_mark_node;
}

/* We are using a reference VAL for its value. Bash that reference all the
   way down to its lowest form.  */

tree
convert_from_reference (val)
     tree val;
{
  tree type = TREE_TYPE (val);

  if (TREE_CODE (type) == OFFSET_TYPE)
    type = TREE_TYPE (type);
  if (TREE_CODE (type) == REFERENCE_TYPE)
    return build_indirect_ref (val, NULL_PTR);
  return val;
}

/* Call this when we know (for any reason) that expr is not, in fact,
   zero.  This routine is like convert_pointer_to, but it pays
   attention to which specific instance of what type we want to
   convert to.  This routine should eventually become
   convert_to_pointer after all references to convert_to_pointer
   are removed.  */

tree
convert_pointer_to_real (binfo, expr)
     tree binfo, expr;
{
  register tree intype = TREE_TYPE (expr);
  tree ptr_type;
  tree type, rval;

  if (intype == error_mark_node)
    return error_mark_node;

  if (TREE_CODE (binfo) == TREE_VEC)
    type = BINFO_TYPE (binfo);
  else if (IS_AGGR_TYPE (binfo))
    {
      type = binfo;
    }
  else
    {
      type = binfo;
      binfo = NULL_TREE;
    }

  ptr_type = cp_build_qualified_type (type,
				      CP_TYPE_QUALS (TREE_TYPE (intype)));
  ptr_type = build_pointer_type (ptr_type);
  if (same_type_p (ptr_type, TYPE_MAIN_VARIANT (intype)))
    return expr;

  my_friendly_assert (!integer_zerop (expr), 191);

  intype = TYPE_MAIN_VARIANT (TREE_TYPE (intype));
  if (TREE_CODE (type) == RECORD_TYPE
      && TREE_CODE (intype) == RECORD_TYPE
      && type != intype)
    {
      tree path;
      int distance
	= get_base_distance (binfo, intype, 0, &path);

      /* This function shouldn't be called with unqualified arguments
	 but if it is, give them an error message that they can read.  */
      if (distance < 0)
	{
	  cp_error ("cannot convert a pointer of type `%T' to a pointer of type `%T'",
		    intype, type);

	  if (distance == -2)
	    cp_error ("because `%T' is an ambiguous base class", type);
	  return error_mark_node;
	}

      return build_vbase_path (PLUS_EXPR, ptr_type, expr, path, 1);
    }
  rval = build1 (NOP_EXPR, ptr_type,
		 TREE_CODE (expr) == NOP_EXPR ? TREE_OPERAND (expr, 0) : expr);
  TREE_CONSTANT (rval) = TREE_CONSTANT (expr);
  return rval;
}

/* Call this when we know (for any reason) that expr is
   not, in fact, zero.  This routine gets a type out of the first
   argument and uses it to search for the type to convert to.  If there
   is more than one instance of that type in the expr, the conversion is
   ambiguous.  This routine should eventually go away, and all
   callers should use convert_to_pointer_real.  */

tree
convert_pointer_to (binfo, expr)
     tree binfo, expr;
{
  tree type;

  if (TREE_CODE (binfo) == TREE_VEC)
    type = BINFO_TYPE (binfo);
  else if (IS_AGGR_TYPE (binfo))
      type = binfo;
  else
      type = binfo;
  return convert_pointer_to_real (type, expr);
}

/* C++ conversions, preference to static cast conversions.  */

tree
cp_convert (type, expr)
     tree type, expr;
{
  return ocp_convert (type, expr, CONV_OLD_CONVERT, LOOKUP_NORMAL);
}

/* Conversion...

   FLAGS indicates how we should behave.  */

tree
ocp_convert (type, expr, convtype, flags)
     tree type, expr;
     int convtype, flags;
{
  register tree e = expr;
  register enum tree_code code = TREE_CODE (type);

  if (e == error_mark_node
      || TREE_TYPE (e) == error_mark_node)
    return error_mark_node;

  if (TREE_READONLY_DECL_P (e))
    e = decl_constant_value (e);

  if (IS_AGGR_TYPE (type) && (convtype & CONV_FORCE_TEMP)
      /* Some internal structures (vtable_entry_type, sigtbl_ptr_type)
	 don't go through finish_struct, so they don't have the synthesized
	 constructors.  So don't force a temporary.  */
      && TYPE_HAS_CONSTRUCTOR (type))
    /* We need a new temporary; don't take this shortcut.  */;
  else if (TYPE_MAIN_VARIANT (type) == TYPE_MAIN_VARIANT (TREE_TYPE (e)))
    {
      if (same_type_p (type, TREE_TYPE (e)))
	/* The call to fold will not always remove the NOP_EXPR as
	   might be expected, since if one of the types is a typedef;
	   the comparsion in fold is just equality of pointers, not a
	   call to comptypes.  We don't call fold in this case because
	   that can result in infinite recursion; fold will call
	   convert, which will call ocp_convert, etc.  */
	return e;
      else
	return fold (build1 (NOP_EXPR, type, e));
    }

  if (code == VOID_TYPE && (convtype & CONV_STATIC))
    {
      e = require_complete_type_in_void (e);
      if (e != error_mark_node)
        e = build1 (CONVERT_EXPR, void_type_node, e);

      return e;
    }

#if 0
  /* This is incorrect.  A truncation can't be stripped this way.
     Extensions will be stripped by the use of get_unwidened.  */
  if (TREE_CODE (e) == NOP_EXPR)
    return cp_convert (type, TREE_OPERAND (e, 0));
#endif

  /* Just convert to the type of the member.  */
  if (code == OFFSET_TYPE)
    {
      type = TREE_TYPE (type);
      code = TREE_CODE (type);
    }

#if 0
  if (code == REFERENCE_TYPE)
    return fold (convert_to_reference (type, e, convtype, flags, NULL_TREE));
  else if (TREE_CODE (TREE_TYPE (e)) == REFERENCE_TYPE)
    e = convert_from_reference (e);
#endif

  if (TREE_CODE (e) == OFFSET_REF)
    e = resolve_offset_ref (e);

  if (INTEGRAL_CODE_P (code))
    {
      tree intype = TREE_TYPE (e);
      /* enum = enum, enum = int, enum = float, (enum)pointer are all
         errors.  */
      if (TREE_CODE (type) == ENUMERAL_TYPE
	  && ((ARITHMETIC_TYPE_P (intype) && ! (convtype & CONV_STATIC))
	      || (TREE_CODE (intype) == POINTER_TYPE)))
	{
	  cp_pedwarn ("conversion from `%#T' to `%#T'", intype, type);

	  if (flag_pedantic_errors)
	    return error_mark_node;
	}
      if (IS_AGGR_TYPE (intype))
	{
	  tree rval;
	  rval = build_type_conversion (type, e, 1);
	  if (rval)
	    return rval;
	  if (flags & LOOKUP_COMPLAIN)
	    cp_error ("`%#T' used where a `%T' was expected", intype, type);
	  if (flags & LOOKUP_SPECULATIVELY)
	    return NULL_TREE;
	  return error_mark_node;
	}
      if (code == BOOLEAN_TYPE)
	{
	  /* Common Ada/Pascal programmer's mistake.  We always warn
             about this since it is so bad.  */
	  if (TREE_CODE (expr) == FUNCTION_DECL)
	    cp_warning ("the address of `%D', will always be `true'", expr);
	  return truthvalue_conversion (e);
	}
      return fold (convert_to_integer (type, e));
    }
  if (code == POINTER_TYPE || code == REFERENCE_TYPE
      || TYPE_PTRMEMFUNC_P (type))
    return fold (cp_convert_to_pointer (type, e));
  if (code == REAL_TYPE || code == COMPLEX_TYPE)
    {
      if (IS_AGGR_TYPE (TREE_TYPE (e)))
	{
	  tree rval;