call.c

gcc库的原代码,对编程有很大帮助.

/* Functions related to invoking methods and overloaded functions.
   Copyright (C) 1987, 1992, 1993, 1994, 1995 Free Software Foundation, Inc.
   Contributed by Michael Tiemann ([e-mail]) and
   hacked by Brendan Kehoe ([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.  */


/* High-level class interface. */

#include "config.h"
#include "tree.h"
#include <stdio.h>
#include "cp-tree.h"
#include "class.h"
#include "output.h"
#include "flags.h"

#include "obstack.h"
#define obstack_chunk_alloc xmalloc
#define obstack_chunk_free free

extern void sorry ();

extern int inhibit_warnings;
extern int flag_assume_nonnull_objects;
extern tree ctor_label, dtor_label;

/* From typeck.c:  */
extern tree unary_complex_lvalue ();

/* Compute the ease with which a conversion can be performed
   between an expected and the given type.  */
static struct harshness_code convert_harshness ();

#define EVIL_RETURN(ARG)	((ARG).code = EVIL_CODE, (ARG))
#define STD_RETURN(ARG)		((ARG).code = STD_CODE, (ARG))
#define QUAL_RETURN(ARG)	((ARG).code = QUAL_CODE, (ARG))
#define TRIVIAL_RETURN(ARG)	((ARG).code = TRIVIAL_CODE, (ARG))
#define ZERO_RETURN(ARG)	((ARG).code = 0, (ARG))

/* Ordering function for overload resolution.  Compare two candidates
   by gross quality.  */
int
rank_for_overload (x, y)
     struct candidate *x, *y;
{
  if (y->h.code & (EVIL_CODE|ELLIPSIS_CODE|USER_CODE))
    return y->h.code - x->h.code;
  if (x->h.code & (EVIL_CODE|ELLIPSIS_CODE|USER_CODE))
    return -1;

  /* This is set by compute_conversion_costs, for calling a non-const
     member function from a const member function.  */
  if ((y->harshness[0].code & CONST_CODE) ^ (x->harshness[0].code & CONST_CODE))
    return y->harshness[0].code - x->harshness[0].code;

  if (y->h.code & STD_CODE)
    {
      if (x->h.code & STD_CODE)
	return y->h.distance - x->h.distance;
      return 1;
    }
  if (x->h.code & STD_CODE)
    return -1;

  return y->h.code - x->h.code;
}

/* Compare two candidates, argument by argument.  */
int
rank_for_ideal (x, y)
     struct candidate *x, *y;
{
  int i;

  if (x->h_len != y->h_len)
    abort ();

  for (i = 0; i < x->h_len; i++)
    {
      if (y->harshness[i].code - x->harshness[i].code)
	return y->harshness[i].code - x->harshness[i].code;
      if ((y->harshness[i].code & STD_CODE)
	  && (y->harshness[i].distance - x->harshness[i].distance))
	return y->harshness[i].distance - x->harshness[i].distance;

      /* They're both the same code.  Now see if we're dealing with an
	 integral promotion that needs a finer grain of accuracy.  */
      if (y->harshness[0].code & PROMO_CODE
	  && (y->harshness[i].int_penalty ^ x->harshness[i].int_penalty))
	return y->harshness[i].int_penalty - x->harshness[i].int_penalty;
    }
  return 0;
}

/* TYPE is the type we wish to convert to.  PARM is the parameter
   we have to work with.  We use a somewhat arbitrary cost function
   to measure this conversion.  */
static struct harshness_code
convert_harshness (type, parmtype, parm)
     register tree type, parmtype;
     tree parm;
{
  struct harshness_code h;
  register enum tree_code codel;
  register enum tree_code coder;
  int lvalue;

  h.code = 0;
  h.distance = 0;
  h.int_penalty = 0;

#ifdef GATHER_STATISTICS
  n_convert_harshness++;
#endif

  if (TREE_CODE (parmtype) == REFERENCE_TYPE)
    {
      if (parm)
	parm = convert_from_reference (parm);
      parmtype = TREE_TYPE (parmtype);
      lvalue = 1;
    }
  else if (parm)
    lvalue = lvalue_p (parm);
  else
    lvalue = 0;

  if (TYPE_PTRMEMFUNC_P (type))
    type = TYPE_PTRMEMFUNC_FN_TYPE (type);
  if (TYPE_PTRMEMFUNC_P (parmtype))
    parmtype = TYPE_PTRMEMFUNC_FN_TYPE (parmtype);

  codel = TREE_CODE (type);
  coder = TREE_CODE (parmtype);

  if (TYPE_MAIN_VARIANT (parmtype) == TYPE_MAIN_VARIANT (type))
    return ZERO_RETURN (h);

  if (coder == ERROR_MARK)
    return EVIL_RETURN (h);

  if (codel == REFERENCE_TYPE)
    {
      tree ttl, ttr;
      int constp = parm ? TREE_READONLY (parm) : TYPE_READONLY (parmtype);
      int volatilep = (parm ? TREE_THIS_VOLATILE (parm)
		       : TYPE_VOLATILE (parmtype));
      register tree intype = TYPE_MAIN_VARIANT (parmtype);
      register enum tree_code form = TREE_CODE (intype);
      int penalty = 0;

      ttl = TREE_TYPE (type);

      /* Only allow const reference binding if we were given a parm to deal
         with, since it isn't really a conversion.  This is a hack to
         prevent build_type_conversion from finding this conversion, but
         still allow overloading to find it.  */
      if (! lvalue && ! (parm && TYPE_READONLY (ttl)))
	return EVIL_RETURN (h);

      if (TYPE_READONLY (ttl) < constp
	  || TYPE_VOLATILE (ttl) < volatilep)
	return EVIL_RETURN (h);

      /* When passing a non-const argument into a const reference, dig it a
	 little, so a non-const reference is preferred over this one.  */
      penalty = ((TYPE_READONLY (ttl) > constp)
		 + (TYPE_VOLATILE (ttl) > volatilep));

      ttl = TYPE_MAIN_VARIANT (ttl);

      if (form == OFFSET_TYPE)
	{
	  intype = TREE_TYPE (intype);
	  form = TREE_CODE (intype);
	}

      ttr = intype;

      if (TREE_CODE (ttl) == ARRAY_TYPE && TREE_CODE (ttr) == ARRAY_TYPE)
	{
	  if (comptypes (ttl, ttr, 1))
	    return ZERO_RETURN (h);
	  return EVIL_RETURN (h);
	}

      h = convert_harshness (ttl, ttr, NULL_TREE);
      if (penalty && h.code == 0)
	{
	  h.code = QUAL_CODE;
	  h.int_penalty = penalty;
	}
      return h;
    }

  if (codel == POINTER_TYPE && fntype_p (parmtype))
    {
      tree p1, p2;
      struct harshness_code h1, h2;

      /* Get to the METHOD_TYPE or FUNCTION_TYPE that this might be.  */
      type = TREE_TYPE (type);

      if (coder == POINTER_TYPE)
	{
	  parmtype = TREE_TYPE (parmtype);
	  coder = TREE_CODE (parmtype);
	}

      if (coder != TREE_CODE (type))
	return EVIL_RETURN (h);

      if (type != parmtype && coder == METHOD_TYPE)
	{
	  tree ttl = TYPE_METHOD_BASETYPE (type);
	  tree ttr = TYPE_METHOD_BASETYPE (parmtype);

	  int b_or_d = get_base_distance (ttr, ttl, 0, 0);
	  if (b_or_d < 0)
	    {
	      b_or_d = get_base_distance (ttl, ttr, 0, 0);
	      if (b_or_d < 0)
		return EVIL_RETURN (h);
	      h.distance = -b_or_d;
	    }
	  else
	    h.distance = b_or_d;
	  h.code = STD_CODE;

	  type = build_function_type
	    (TREE_TYPE (type), TREE_CHAIN (TYPE_ARG_TYPES (type)));
	  parmtype = build_function_type
	    (TREE_TYPE (parmtype), TREE_CHAIN (TYPE_ARG_TYPES (parmtype)));
	}

      /* We allow the default conversion between function type
	 and pointer-to-function type for free.  */
      if (comptypes (type, parmtype, 1))
	return h;

      if (pedantic)
	return EVIL_RETURN (h);

      /* Compare return types.  */
      p1 = TREE_TYPE (type);
      p2 = TREE_TYPE (parmtype);
      h2 = convert_harshness (p1, p2, NULL_TREE);
      if (h2.code & EVIL_CODE)
	return h2;

      h1.code = TRIVIAL_CODE;
      h1.distance = 0;

      if (h2.distance != 0)
	{
	  tree binfo;

	  /* This only works for pointers.  */
	  if (TREE_CODE (p1) != POINTER_TYPE
	      && TREE_CODE (p1) != REFERENCE_TYPE)
	    return EVIL_RETURN (h);

	  p1 = TREE_TYPE (p1);
	  p2 = TREE_TYPE (p2);
	  /* Don't die if we happen to be dealing with void*.  */
	  if (!IS_AGGR_TYPE (p1) || !IS_AGGR_TYPE (p2))
	    return EVIL_RETURN (h);
	  if (h2.distance < 0)
	    binfo = get_binfo (p2, p1, 0);
	  else
	    binfo = get_binfo (p1, p2, 0);

	  if (! BINFO_OFFSET_ZEROP (binfo))
	    {
#if 0
	      static int explained = 0;
	      if (h2.distance < 0)
		message_2_types (sorry, "cannot cast `%s' to `%s' at function call site", p2, p1);
	      else
		message_2_types (sorry, "cannot cast `%s' to `%s' at function call site", p1, p2);

	      if (! explained++)
		sorry ("(because pointer values change during conversion)");
#endif
	      return EVIL_RETURN (h);
	    }
	}

      h1.code |= h2.code;
      if (h2.distance > h1.distance)
	h1.distance = h2.distance;

      p1 = TYPE_ARG_TYPES (type);
      p2 = TYPE_ARG_TYPES (parmtype);
      while (p1 && TREE_VALUE (p1) != void_type_node
	     && p2 && TREE_VALUE (p2) != void_type_node)
	{
	  h2 = convert_harshness (TREE_VALUE (p1), TREE_VALUE (p2),
				       NULL_TREE);
	  if (h2.code & EVIL_CODE)
	    return h2;

	  if (h2.distance)
	    {
	      /* This only works for pointers and references. */
	      if (TREE_CODE (TREE_VALUE (p1)) != POINTER_TYPE
		  && TREE_CODE (TREE_VALUE (p1)) != REFERENCE_TYPE)
		return EVIL_RETURN (h);
	      h2.distance = - h2.distance;
	    }

	  h1.code |= h2.code;
	  if (h2.distance > h1.distance)
	    h1.distance = h2.distance;
	  p1 = TREE_CHAIN (p1);
	  p2 = TREE_CHAIN (p2);
	}
      if (p1 == p2)
	return h1;
      if (p2)
	{
	  if (p1)
	    return EVIL_RETURN (h);
	  h1.code |= ELLIPSIS_CODE;
	  return h1;
	}
      if (p1)
	{
	  if (TREE_PURPOSE (p1) == NULL_TREE)
	    h1.code |= EVIL_CODE;
	  return h1;
	}
    }
  else if (codel == POINTER_TYPE && coder == OFFSET_TYPE)
    {
      tree ttl, ttr;

      /* Get to the OFFSET_TYPE that this might be.  */
      type = TREE_TYPE (type);

      if (coder != TREE_CODE (type))
	return EVIL_RETURN (h);

      ttl = TYPE_OFFSET_BASETYPE (type);
      ttr = TYPE_OFFSET_BASETYPE (parmtype);

      if (ttl == ttr)
	h.code = 0;
      else
	{
	  int b_or_d = get_base_distance (ttr, ttl, 0, 0);
	  if (b_or_d < 0)
	    {
	      b_or_d = get_base_distance (ttl, ttr, 0, 0);
	      if (b_or_d < 0)
		return EVIL_RETURN (h);
	      h.distance = -b_or_d;
	    }
	  else
	    h.distance = b_or_d;
	  h.code = STD_CODE;
	}

      /* Now test the OFFSET_TYPE's target compatibility.  */
      type = TREE_TYPE (type);
      parmtype = TREE_TYPE (parmtype);
    }

  if (coder == UNKNOWN_TYPE)
    {
      if (codel == FUNCTION_TYPE
	  || codel == METHOD_TYPE
	  || (codel == POINTER_TYPE
	      && (TREE_CODE (TREE_TYPE (type)) == FUNCTION_TYPE
		  || TREE_CODE (TREE_TYPE (type)) == METHOD_TYPE)))
	return TRIVIAL_RETURN (h);
      return EVIL_RETURN (h);
    }

  if (coder == VOID_TYPE)
    return EVIL_RETURN (h);

  if (codel == BOOLEAN_TYPE)
    {
      if (INTEGRAL_CODE_P (coder) || coder == REAL_TYPE)
	return STD_RETURN (h);
      else if (coder == POINTER_TYPE || coder == OFFSET_TYPE)
	{
	  /* Make this worse than any conversion to another pointer.
	     FIXME this is how I think the language should work, but it may not
	     end up being how the language is standardized (jason 1/30/95).  */
	  h.distance = 32767;
	  return STD_RETURN (h);
	}
      return EVIL_RETURN (h);
    }

  if (INTEGRAL_CODE_P (codel))
    {
      /* Control equivalence of ints an enums.  */

      if (codel == ENUMERAL_TYPE
	  && flag_int_enum_equivalence == 0)
	{
	  /* Enums can be converted to ints, but not vice-versa.  */
	  if (coder != ENUMERAL_TYPE
	      || TYPE_MAIN_VARIANT (type) != TYPE_MAIN_VARIANT (parmtype))
	    return EVIL_RETURN (h);
	}

      /* else enums and ints (almost) freely interconvert.  */

      if (INTEGRAL_CODE_P (coder))
	{
	  if (TYPE_MAIN_VARIANT (type)
	      == TYPE_MAIN_VARIANT (type_promotes_to (parmtype)))
	    {
	      h.code = PROMO_CODE;
#if 0 /* What purpose does this serve?  -jason */
	      /* A char, short, wchar_t, etc., should promote to an int if
		 it can handle it, otherwise to an unsigned.  So we'll make
		 an unsigned.  */
	      if (type != integer_type_node)
		h.int_penalty = 1;
#endif
	    }
	  else
	    h.code = STD_CODE;
	    
	  return h;
	}
      else if (coder == REAL_TYPE)
	{
	  h.code = STD_CODE;
	  h.distance = 0;
	  return h;
	}
    }