call.c

gcc-2.95.3 Linux下最常用的C编译器

    }

  types[0] = types[1] = NULL_TREE;

  for (i = 0; i < 2; ++i)
    {
      if (! args[i])
	;
      else if (IS_AGGR_TYPE (argtypes[i]))
	{
	  tree convs;

	  if (i == 0 && code == MODIFY_EXPR && code2 == NOP_EXPR)
	    return candidates;

	  convs = lookup_conversions (argtypes[i]);

	  if (code == COND_EXPR)
	    {
	      if (real_lvalue_p (args[i]))
		types[i] = scratch_tree_cons
		  (NULL_TREE, build_reference_type (argtypes[i]), types[i]);

	      types[i] = scratch_tree_cons
		(NULL_TREE, TYPE_MAIN_VARIANT (argtypes[i]), types[i]);
	    }

	  else if (! convs)
	    return candidates;

	  for (; convs; convs = TREE_CHAIN (convs))
	    {
	      type = TREE_TYPE (TREE_TYPE (OVL_CURRENT (TREE_VALUE (convs))));

	      if (i == 0 && ref1
		  && (TREE_CODE (type) != REFERENCE_TYPE
		      || CP_TYPE_CONST_P (TREE_TYPE (type))))
		continue;

	      if (code == COND_EXPR && TREE_CODE (type) == REFERENCE_TYPE)
		types[i] = scratch_tree_cons (NULL_TREE, type, types[i]);

	      type = non_reference (type);
	      if (i != 0 || ! ref1)
		{
		  type = TYPE_MAIN_VARIANT (type_decays_to (type));
		  if (code == COND_EXPR && TREE_CODE (type) == ENUMERAL_TYPE)
		    types[i] = scratch_tree_cons (NULL_TREE, type, types[i]);
		  if (INTEGRAL_TYPE_P (type))
		    type = type_promotes_to (type);
		}

	      if (! value_member (type, types[i]))
		types[i] = scratch_tree_cons (NULL_TREE, type, types[i]);
	    }
	}
      else
	{
	  if (code == COND_EXPR && real_lvalue_p (args[i]))
	    types[i] = scratch_tree_cons
	      (NULL_TREE, build_reference_type (argtypes[i]), types[i]);
	  type = non_reference (argtypes[i]);
	  if (i != 0 || ! ref1)
	    {
	      type = TYPE_MAIN_VARIANT (type_decays_to (type));
	      if (code == COND_EXPR && TREE_CODE (type) == ENUMERAL_TYPE)
		types[i] = scratch_tree_cons (NULL_TREE, type, types[i]);
	      if (INTEGRAL_TYPE_P (type))
		type = type_promotes_to (type);
	    }
	  types[i] = scratch_tree_cons (NULL_TREE, type, types[i]);
	}
    }

  for (; types[0]; types[0] = TREE_CHAIN (types[0]))
    {
      if (types[1])
	for (type = types[1]; type; type = TREE_CHAIN (type))
	  candidates = add_builtin_candidate
	    (candidates, code, code2, fnname, TREE_VALUE (types[0]),
	     TREE_VALUE (type), args, argtypes, flags);
      else
	candidates = add_builtin_candidate
	  (candidates, code, code2, fnname, TREE_VALUE (types[0]),
	   NULL_TREE, args, argtypes, flags);
    }

  return candidates;
}


/* If TMPL can be successfully instantiated as indicated by
   EXPLICIT_TARGS and ARGLIST, adds the instantiation to CANDIDATES.

   TMPL is the template.  EXPLICIT_TARGS are any explicit template
   arguments.  ARGLIST is the arguments provided at the call-site.
   The RETURN_TYPE is the desired type for conversion operators.  If
   OBJ is NULL_TREE, FLAGS are as for add_function_candidate.  If an
   OBJ is supplied, FLAGS are ignored, and OBJ is as for
   add_conv_candidate.  */

static struct z_candidate*
add_template_candidate_real (candidates, tmpl, explicit_targs,
			     arglist, return_type, flags,
			     obj, strict)
     struct z_candidate *candidates;
     tree tmpl, explicit_targs, arglist, return_type;
     int flags;
     tree obj;
     unification_kind_t strict;
{
  int ntparms = DECL_NTPARMS (tmpl);
  tree targs = make_scratch_vec (ntparms);
  struct z_candidate *cand;
  int i;
  tree fn;

  i = fn_type_unification (tmpl, explicit_targs, targs, arglist,
			   return_type, strict);

  if (i != 0)
    return candidates;

  fn = instantiate_template (tmpl, targs);
  if (fn == error_mark_node)
    return candidates;

  if (obj != NULL_TREE)
    /* Aha, this is a conversion function.  */
    cand = add_conv_candidate (candidates, fn, obj, arglist);
  else
    cand = add_function_candidate (candidates, fn, arglist, flags);
  if (DECL_TI_TEMPLATE (fn) != tmpl)
    /* This situation can occur if a member template of a template
       class is specialized.  Then, instantiate_template might return
       an instantiation of the specialization, in which case the
       DECL_TI_TEMPLATE field will point at the original
       specialization.  For example:

	 template <class T> struct S { template <class U> void f(U);
				       template <> void f(int) {}; };
	 S<double> sd;
	 sd.f(3);

       Here, TMPL will be template <class U> S<double>::f(U).
       And, instantiate template will give us the specialization
       template <> S<double>::f(int).  But, the DECL_TI_TEMPLATE field
       for this will point at template <class T> template <> S<T>::f(int),
       so that we can find the definition.  For the purposes of
       overload resolution, however, we want the original TMPL.  */
    cand->template = tree_cons (tmpl, targs, NULL_TREE);
  else
    cand->template = DECL_TEMPLATE_INFO (fn);

  return cand;
}


static struct z_candidate *
add_template_candidate (candidates, tmpl, explicit_targs, 
			arglist, return_type, flags, strict)
     struct z_candidate *candidates;
     tree tmpl, explicit_targs, arglist, return_type;
     int flags;
     unification_kind_t strict;
{
  return 
    add_template_candidate_real (candidates, tmpl, explicit_targs,
				 arglist, return_type, flags,
				 NULL_TREE, strict);
}


static struct z_candidate *
add_template_conv_candidate (candidates, tmpl, obj, arglist, return_type)
     struct z_candidate *candidates;
     tree tmpl, obj, arglist, return_type;
{
  return 
    add_template_candidate_real (candidates, tmpl, NULL_TREE, arglist,
				 return_type, 0, obj, DEDUCE_CONV);
}


static int
any_viable (cands)
     struct z_candidate *cands;
{
  for (; cands; cands = cands->next)
    if (pedantic ? cands->viable == 1 : cands->viable)
      return 1;
  return 0;
}

static struct z_candidate *
splice_viable (cands)
     struct z_candidate *cands;
{
  struct z_candidate **p = &cands;

  for (; *p; )
    {
      if (pedantic ? (*p)->viable == 1 : (*p)->viable)
	p = &((*p)->next);
      else
	*p = (*p)->next;
    }

  return cands;
}

static tree
build_this (obj)
     tree obj;
{
  /* Fix this to work on non-lvalues.  */
  if (IS_SIGNATURE_POINTER (TREE_TYPE (obj))
      || IS_SIGNATURE_REFERENCE (TREE_TYPE (obj)))
    return obj;
  else
    return build_unary_op (ADDR_EXPR, obj, 0);
}

static void
print_z_candidates (candidates)
     struct z_candidate *candidates;
{
  const char *str = "candidates are:";
  for (; candidates; candidates = candidates->next)
    {
      if (TREE_CODE (candidates->fn) == IDENTIFIER_NODE)
	{
	  if (candidates->fn == ansi_opname [COND_EXPR])
	    cp_error ("%s %D(%T, %T, %T) <builtin>", str, candidates->fn,
		      TREE_TYPE (TREE_VEC_ELT (candidates->convs, 0)),
		      TREE_TYPE (TREE_VEC_ELT (candidates->convs, 1)),
		      TREE_TYPE (TREE_VEC_ELT (candidates->convs, 2)));
	  else if (TREE_VEC_LENGTH (candidates->convs) == 2)
	    cp_error ("%s %D(%T, %T) <builtin>", str, candidates->fn,
		      TREE_TYPE (TREE_VEC_ELT (candidates->convs, 0)),
		      TREE_TYPE (TREE_VEC_ELT (candidates->convs, 1)));
	  else
	    cp_error ("%s %D(%T) <builtin>", str, candidates->fn,
		      TREE_TYPE (TREE_VEC_ELT (candidates->convs, 0)));
	}
      else if (TYPE_P (candidates->fn))
	cp_error ("%s %T <conversion>", str, candidates->fn);
      else
	cp_error_at ("%s %+#D%s", str, candidates->fn,
		     candidates->viable == -1 ? " <near match>" : "");
      str = "               "; 
    }
}

/* Returns the best overload candidate to perform the requested
   conversion.  This function is used for three the overloading situations
   described in [over.match.copy], [over.match.conv], and [over.match.ref].
   If TOTYPE is a REFERENCE_TYPE, we're trying to find an lvalue binding as
   per [dcl.init.ref], so we ignore temporary bindings.  */

static struct z_candidate *
build_user_type_conversion_1 (totype, expr, flags)
     tree totype, expr;
     int flags;
{
  struct z_candidate *candidates, *cand;
  tree fromtype = TREE_TYPE (expr);
  tree ctors = NULL_TREE, convs = NULL_TREE, *p;
  tree args = NULL_TREE;
  tree templates = NULL_TREE;

  if (IS_AGGR_TYPE (totype))
    ctors = lookup_fnfields (TYPE_BINFO (totype), ctor_identifier, 0);
  if (IS_AGGR_TYPE (fromtype)
      && (! IS_AGGR_TYPE (totype) || ! DERIVED_FROM_P (totype, fromtype)))
    convs = lookup_conversions (fromtype);

  candidates = 0;
  flags |= LOOKUP_NO_CONVERSION;

  if (ctors)
    {
      tree t = build_int_2 (0, 0);
      TREE_TYPE (t) = build_pointer_type (totype);
      args = build_scratch_list (NULL_TREE, expr);
      if (TYPE_USES_PVBASES (totype) && !flag_vtable_thunks_compat)
	{
	  args = scratch_tree_cons (NULL_TREE, vlist_zero_node, args);
	  flags |= LOOKUP_HAS_VLIST;
	}
      if (TYPE_USES_VIRTUAL_BASECLASSES (totype))
	args = scratch_tree_cons (NULL_TREE, integer_one_node, args);
      args = scratch_tree_cons (NULL_TREE, t, args);

      ctors = TREE_VALUE (ctors);
    }
  for (; ctors; ctors = OVL_NEXT (ctors))
    {
      tree ctor = OVL_CURRENT (ctors);
      if (DECL_NONCONVERTING_P (ctor))
	continue;

      if (TREE_CODE (ctor) == TEMPLATE_DECL) 
	{
	  templates = scratch_tree_cons (NULL_TREE, ctor, templates);
	  candidates = 
	    add_template_candidate (candidates, ctor,
				    NULL_TREE, args, NULL_TREE, flags,
				    DEDUCE_CALL);
	} 
      else 
	candidates = add_function_candidate (candidates, ctor,
					     args, flags); 

      if (candidates) 
	{
	  candidates->second_conv = build1 (IDENTITY_CONV, totype, NULL_TREE);
	  candidates->basetype_path = TYPE_BINFO (totype);
	} 
    }

  if (convs)
    args = build_scratch_list (NULL_TREE, build_this (expr));

  for (; convs; convs = TREE_CHAIN (convs))
    {
      tree fns = TREE_VALUE (convs);
      int convflags = LOOKUP_NO_CONVERSION;
      tree ics;

      /* If we are called to convert to a reference type, we are trying to
	 find an lvalue binding, so don't even consider temporaries.  If
	 we don't find an lvalue binding, the caller will try again to
	 look for a temporary binding.  */
      if (TREE_CODE (totype) == REFERENCE_TYPE)
	convflags |= LOOKUP_NO_TEMP_BIND;

      if (TREE_CODE (OVL_CURRENT (fns)) != TEMPLATE_DECL)
	ics = implicit_conversion
	  (totype, TREE_TYPE (TREE_TYPE (OVL_CURRENT (fns))), 0, convflags);
      else
	/* We can't compute this yet.  */
	ics = error_mark_node;

      if (TREE_CODE (totype) == REFERENCE_TYPE && ics && ICS_BAD_FLAG (ics))
	/* ignore the near match.  */;
      else if (ics)
	for (; fns; fns = OVL_NEXT (fns))
	  {
	    tree fn = OVL_CURRENT (fns);
	    struct z_candidate *old_candidates = candidates;

	    if (TREE_CODE (fn) == TEMPLATE_DECL)
	      {
		templates = scratch_tree_cons (NULL_TREE, fn, templates);
		candidates = 
		  add_template_candidate (candidates, fn, NULL_TREE,
					  args, totype, flags,
					  DEDUCE_CONV);
	      } 
	    else 
	      candidates = add_function_candidate (candidates, fn,
						   args, flags); 

	    if (candidates != old_candidates)
	      {
		if (TREE_CODE (fn) == TEMPLATE_DECL)
		  ics = implicit_conversion
		    (totype, TREE_TYPE (TREE_TYPE (candidates->fn)),
		     0, convflags);

		candidates->second_conv = ics;
		candidates->basetype_path = TREE_PURPOSE (convs);

		if (ics == NULL_TREE)
		  candidates->viable = 0;
		else if (candidates->viable == 1 && ICS_BAD_FLAG (ics))
		  candidates->viable = -1;
	      }
	  }
    }

  if (! any_viable (candidates))
    {
#if 0
      if (flags & LOOKUP_COMPLAIN)
	{
	  if (candidates && ! candidates->next)
	    /* say why this one won't work or try to be loose */;
	  else
	    cp_error ("no viable candidates");
	}
#endif

      return 0;
    }

  candidates = splice_viable (candidates);
  cand = tourney (candidates);

  if (cand == 0)
    {
      if (flags & LOOKUP_COMPLAIN)
	{
	  cp_error ("conversion from `%T' to `%T' is ambiguous",
		    fromtype, totype);
	  print_z_candidates (candidates);
	}

      cand = candidates;	/* any one will do */
      cand->second_conv = build1 (AMBIG_CONV, totype, expr);
      ICS_USER_FLAG (cand->second_conv) = 1;
      ICS_BAD_FLAG (cand->second_conv) = 1;

      return cand;
    }

  for (p = &(cand->second_conv); TREE_CODE (*p) != IDENTITY_CONV; )
    p = &(TREE_OPERAND (*p, 0));

  /* Pedantically, normal function declarations are never considered
     to refer to template instantiations, so we only do this with
     -fguiding-decls.  */ 
  if (flag_guiding_decls && templates && ! cand->template 
      && !DECL_INITIAL (cand->fn) 
      && TREE_CODE (TREE_TYPE (cand->fn)) != METHOD_TYPE)
    add_maybe_template (cand->fn, templates);

  *p = build
    (USER_CONV,
     (DECL_CONSTRUCTOR_P (cand->fn)
      ? totype : non_reference (TREE_TYPE (TREE_TYPE (cand->fn)))),
     expr, build_expr_ptr_wrapper (cand));
  ICS_USER_FLAG (cand->second_conv) = 1;
  if (cand->viable == -1)
    ICS_BAD_FLAG (cand->second_conv) = 1;

  return cand;
}

tree
build_user_type_conversion (totype, expr, flags)
     tree totype, expr;
     int flags;
{
  struct z_candidate *cand
    = build_user_type_conversion_1 (totype, expr, flags);

  if (c