path: root/gcc/cp/friend.c

/* Help friends in C++.
   Copyright (C) 1997, 1998, 1999, 2000, 2001, 2002, 2003
   Free Software Foundation, Inc.

This file is part of GCC.

GCC 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.

GCC 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 GCC; see the file COPYING.  If not, write to
the Free Software Foundation, 59 Temple Place - Suite 330,
Boston, MA 02111-1307, USA.  */

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

/* Friend data structures are described in cp-tree.h.  */

/* Returns nonzero if SUPPLICANT is a friend of TYPE.  */

int
is_friend (tree type, tree supplicant)
{
  int declp;
  tree list;
  tree context;

  if (supplicant == NULL_TREE || type == NULL_TREE)
    return 0;

  declp = DECL_P (supplicant);

  if (declp)
    /* It's a function decl.  */
    {
      tree list = DECL_FRIENDLIST (TYPE_MAIN_DECL (type));
      tree name = DECL_NAME (supplicant);

      for (; list ; list = TREE_CHAIN (list))
	{
	  if (name == FRIEND_NAME (list))
	    {
	      tree friends = FRIEND_DECLS (list);
	      for (; friends ; friends = TREE_CHAIN (friends))
		{
		  tree friend = TREE_VALUE (friends);

		  if (friend == NULL_TREE)
		    continue;

		  if (supplicant == friend)
		    return 1;

		  if (is_specialization_of_friend (supplicant, friend))
		    return 1;
		}
	      break;
	    }
	}
    }
  else
    /* It's a type.  */
    {
      /* Nested classes are implicitly friends of their enclosing types, as
	 per core issue 45 (this is a change from the standard).  */
      for (context = supplicant;
	   context && TYPE_P (context);
	   context = TYPE_CONTEXT (context))
	if (type == context)
	  return 1;
      
      list = CLASSTYPE_FRIEND_CLASSES (TREE_TYPE (TYPE_MAIN_DECL (type)));
      for (; list ; list = TREE_CHAIN (list))
	{
	  tree t = TREE_VALUE (list);

	  if (TREE_CODE (t) == TEMPLATE_DECL ? 
	      is_specialization_of (TYPE_MAIN_DECL (supplicant), t) :
	      same_type_p (supplicant, t))
	    return 1;
	}
    }      

  if (declp && DECL_FUNCTION_MEMBER_P (supplicant))
    context = DECL_CONTEXT (supplicant);
  else if (! declp)
    /* Local classes have the same access as the enclosing function.  */
    context = decl_function_context (TYPE_MAIN_DECL (supplicant));
  else
    context = NULL_TREE;

  /* A namespace is not friend to anybody.  */
  if (context && TREE_CODE (context) == NAMESPACE_DECL)
    context = NULL_TREE;

  if (context)
    return is_friend (type, context);

  return 0;
}

/* Add a new friend to the friends of the aggregate type TYPE.
   DECL is the FUNCTION_DECL of the friend being added.

   If COMPLAIN is true, warning about duplicate friend is issued.
   We want to have this diagnostics during parsing but not
   when a template is being instantiated.  */

void
add_friend (tree type, tree decl, bool complain)
{
  tree typedecl;
  tree list;
  tree name;

  if (decl == error_mark_node)
    return;

  typedecl = TYPE_MAIN_DECL (type);
  list = DECL_FRIENDLIST (typedecl);
  name = DECL_NAME (decl);
  type = TREE_TYPE (typedecl);

  while (list)
    {
      if (name == FRIEND_NAME (list))
	{
	  tree friends = FRIEND_DECLS (list);
	  for (; friends ; friends = TREE_CHAIN (friends))
	    {
	      if (decl == TREE_VALUE (friends))
		{
		  if (complain)
		    warning ("`%D' is already a friend of class `%T'",
			     decl, type);
		  return;
		}
	    }

	  maybe_add_class_template_decl_list (type, decl, /*friend_p=*/1);

	  TREE_VALUE (list) = tree_cons (NULL_TREE, decl,
					 TREE_VALUE (list));
	  return;
	}
      list = TREE_CHAIN (list);
    }

  if (DECL_CLASS_SCOPE_P (decl))
    perform_or_defer_access_check (TYPE_BINFO (DECL_CONTEXT (decl)), decl);

  maybe_add_class_template_decl_list (type, decl, /*friend_p=*/1);

  DECL_FRIENDLIST (typedecl)
    = tree_cons (DECL_NAME (decl), build_tree_list (NULL_TREE, decl),
		 DECL_FRIENDLIST (typedecl));
  if (!uses_template_parms (type))
    DECL_BEFRIENDING_CLASSES (decl) 
      = tree_cons (NULL_TREE, type,
		   DECL_BEFRIENDING_CLASSES (decl));
}

/* Make FRIEND_TYPE a friend class to TYPE.  If FRIEND_TYPE has already
   been defined, we make all of its member functions friends of
   TYPE.  If not, we make it a pending friend, which can later be added
   when its definition is seen.  If a type is defined, then its TYPE_DECL's
   DECL_UNDEFINED_FRIENDS contains a (possibly empty) list of friend
   classes that are not defined.  If a type has not yet been defined,
   then the DECL_WAITING_FRIENDS contains a list of types
   waiting to make it their friend.  Note that these two can both
   be in use at the same time!

   If COMPLAIN is true, warning about duplicate friend is issued.
   We want to have this diagnostics during parsing but not
   when a template is being instantiated.  */

void
make_friend_class (tree type, tree friend_type, bool complain)
{
  tree classes;
  int is_template_friend;

  if (! IS_AGGR_TYPE (friend_type))
    {
      error ("invalid type `%T' declared `friend'", friend_type);
      return;
    }

  if (processing_template_decl > template_class_depth (type))
    /* If the TYPE is a template then it makes sense for it to be
       friends with itself; this means that each instantiation is
       friends with all other instantiations.  */
    {
      if (CLASS_TYPE_P (friend_type)
	  && CLASSTYPE_TEMPLATE_SPECIALIZATION (friend_type)
	  && uses_template_parms (friend_type))
	{
	  /* [temp.friend]
	     Friend declarations shall not declare partial
	     specializations.  */
	  error ("partial specialization `%T' declared `friend'",
		 friend_type);
	  return;
	}
  
      is_template_friend = 1;
    }
  else if (same_type_p (type, friend_type))
    {
      if (complain)
	pedwarn ("class `%T' is implicitly friends with itself",
		 type);
      return;
    }
  else
    is_template_friend = 0;

  /* [temp.friend]

     A friend of a class or class template can be a function or
     class template, a specialization of a function template or
     class template, or an ordinary (nontemplate) function or
     class.  */
  if (!is_template_friend)
    ;/* ok */
  else if (TREE_CODE (friend_type) == TYPENAME_TYPE)
    {
      /* template <class T> friend typename S<T>::X; */
      error ("typename type `%#T' declared `friend'", friend_type);
      return;
    }
  else if (TREE_CODE (friend_type) == TEMPLATE_TYPE_PARM)
    {
      /* template <class T> friend class T; */
      error ("template parameter type `%T' declared `friend'", friend_type);
      return;
    }
  else if (!CLASSTYPE_TEMPLATE_INFO (friend_type))
    {
      /* template <class T> friend class A; where A is not a template */
      error ("`%#T' is not a template", friend_type);
      return;
    }

  if (is_template_friend)
    friend_type = CLASSTYPE_TI_TEMPLATE (friend_type);

  /* See if it is already a friend.  */
  for (classes = CLASSTYPE_FRIEND_CLASSES (type);
       classes;
       classes = TREE_CHAIN (classes))
    {
      tree probe = TREE_VALUE (classes);

      if (TREE_CODE (friend_type) == TEMPLATE_DECL)
	{
	  if (friend_type == probe)
	    {
	      if (complain)
		warning ("`%D' is already a friend of `%T'",
			 probe, type);
	      break;
	    }
	}
      else if (TREE_CODE (probe) != TEMPLATE_DECL)
	{
	  if (same_type_p (probe, friend_type))
	    {
	      if (complain)
		warning ("`%T' is already a friend of `%T'",
			 probe, type);
	      break;
	    }
	}
    }
  
  if (!classes) 
    {
      maybe_add_class_template_decl_list (type, friend_type, /*friend_p=*/1);

      CLASSTYPE_FRIEND_CLASSES (type)
	= tree_cons (NULL_TREE, friend_type, CLASSTYPE_FRIEND_CLASSES (type));
      if (is_template_friend)
	friend_type = TREE_TYPE (friend_type);
      if (!uses_template_parms (type))
	CLASSTYPE_BEFRIENDING_CLASSES (friend_type)
	  = tree_cons (NULL_TREE, type, 
		       CLASSTYPE_BEFRIENDING_CLASSES (friend_type)); 
    }
}

/* Main friend processor. 

   CTYPE is the class this friend belongs to.

   DECLARATOR is the name of the friend.

   DECL is the FUNCTION_DECL that the friend is.

   In case we are parsing a friend which is part of an inline
   definition, we will need to store PARM_DECL chain that comes
   with it into the DECL_ARGUMENTS slot of the FUNCTION_DECL.

   FLAGS is just used for `grokclassfn'.

   QUALS say what special qualifies should apply to the object
   pointed to by `this'.  */

tree
do_friend (tree ctype, tree declarator, tree decl, tree parmdecls,
	   tree attrlist, enum overload_flags flags, tree quals,
	   int funcdef_flag)
{
  /* Every decl that gets here is a friend of something.  */
  DECL_FRIEND_P (decl) = 1;

  if (TREE_CODE (declarator) == TEMPLATE_ID_EXPR)
    {
      declarator = TREE_OPERAND (declarator, 0);
      if (is_overloaded_fn (declarator))
	declarator = DECL_NAME (get_first_fn (declarator));
    }

  if (TREE_CODE (decl) != FUNCTION_DECL)
    abort ();

  if (ctype)
    {
      /* CLASS_TEMPLATE_DEPTH counts the number of template headers for
	 the enclosing class.  FRIEND_DEPTH counts the number of template
	 headers used for this friend declaration.  TEMPLATE_MEMBER_P is
	 true if a template header in FRIEND_DEPTH is intended for
	 DECLARATOR.  For example, the code

	   template <class T> struct A {
	     template <class U> struct B {
	       template <class V> template <class W>
		 friend void C<V>::f(W);
	     };
	   };

	 will eventually give the following results

	 1. CLASS_TEMPLATE_DEPTH equals 2 (for `T' and `U').
	 2. FRIEND_DEPTH equals 2 (for `V' and `W').
	 3. TEMPLATE_MEMBER_P is true (for `W').  */

      int class_template_depth = template_class_depth (current_class_type);
      int friend_depth = processing_template_decl - class_template_depth;
      /* We will figure this out later.  */
      bool template_member_p = false;

      tree cname = TYPE_NAME (ctype);
      if (TREE_CODE (cname) == TYPE_DECL)
	cname = DECL_NAME (cname);

      /* A method friend.  */
      if (flags == NO_SPECIAL && declarator == cname)
	DECL_CONSTRUCTOR_P (decl) = 1;

      /* This will set up DECL_ARGUMENTS for us.  */
      grokclassfn (ctype, decl, flags, quals);

      if (friend_depth)
	{
	  if (!uses_template_parms_level (ctype, class_template_depth
						 + friend_depth))
	    template_member_p = true;
	}

      /* A nested class may declare a member of an enclosing class
	 to be a friend, so we do lookup here even if CTYPE is in
	 the process of being defined.  */
      if (class_template_depth
	  || COMPLETE_TYPE_P (ctype)
	  || TYPE_BEING_DEFINED (ctype))
	{
	  if (DECL_TEMPLATE_INFO (decl))
	    /* DECL is a template specialization.  No need to
	       build a new TEMPLATE_DECL.  */
	    ;
	  else if (class_template_depth)
	    /* We rely on tsubst_friend_function to check the
	       validity of the declaration later.  */
	    decl = push_template_decl_real (decl, /*is_friend=*/1);
	  else
	    decl = check_classfn (ctype, decl, template_member_p);

	  if (template_member_p && decl && TREE_CODE (decl) == FUNCTION_DECL)
	    decl = DECL_TI_TEMPLATE (decl);

	  if (decl)
	    add_friend (current_class_type, decl, /*complain=*/true);
	}
      else
	error ("member `%D' declared as friend before type `%T' defined",
		  decl, ctype);
    }
  /* A global friend.
     @@ or possibly a friend from a base class ?!?  */
  else if (TREE_CODE (decl) == FUNCTION_DECL)
    {
      int is_friend_template = PROCESSING_REAL_TEMPLATE_DECL_P ();

      /* Friends must all go through the overload machinery,
	 even though they may not technically be overloaded.

	 Note that because classes all wind up being top-level
	 in their scope, their friend wind up in top-level scope as well.  */
      DECL_ARGUMENTS (decl) = parmdecls;
      if (funcdef_flag)
	SET_DECL_FRIEND_CONTEXT (decl, current_class_type);

      if (! DECL_USE_TEMPLATE (decl))
	{
	  /* We must check whether the decl refers to template
	     arguments before push_template_decl_real adds a
	     reference to the containing template class.  */
	  int warn = (warn_nontemplate_friend
		      && ! funcdef_flag && ! is_friend_template
		      && current_template_parms
		      && uses_template_parms (decl));

	  if (is_friend_template
	      || template_class_depth (current_class_type) != 0)
	    /* We can't call pushdecl for a template class, since in
	       general, such a declaration depends on template
	       parameters.  Instead, we call pushdecl when the class
	       is instantiated.  */
	    decl = push_template_decl_real (decl, /*is_friend=*/1); 
	  else if (current_function_decl)
	    /* This must be a local class, so pushdecl will be ok, and
	       insert an unqualified friend into the local scope
	       (rather than the containing namespace scope, which the
	       next choice will do).  */
	    decl = pushdecl (decl);
	  else
	    {
	      /* We can't use pushdecl, as we might be in a template
	         class specialization, and pushdecl will insert an
	         unqualified friend decl into the template parameter
	         scope, rather than the namespace containing it.  */
	      tree ns = decl_namespace_context (decl);
	      
	      push_nested_namespace (ns);
	      decl = pushdecl_namespace_level (decl);
	      pop_nested_namespace (ns);
	    }

	  if (warn)
	    {
	      static int explained;
	      warning ("friend declaration `%#D' declares a non-template function", decl);
	      if (! explained)
		{
		  warning ("(if this is not what you intended, make sure the function template has already been declared and add <> after the function name here) -Wno-non-template-friend disables this warning");
		  explained = 1;
		}
	    }
	}

      if (decl == error_mark_node)
	return error_mark_node;
      
      add_friend (current_class_type, 
		  is_friend_template ? DECL_TI_TEMPLATE (decl) : decl,
		  /*complain=*/true);
      DECL_FRIEND_P (decl) = 1;
    }

  /* Unfortunately, we have to handle attributes here.  Normally we would
     handle them in start_decl_1, but since this is a friend decl start_decl_1
     never gets to see it.  */

  /* Set attributes here so if duplicate decl, will have proper attributes.  */
  cplus_decl_attributes (&decl, attrlist, 0);

  return decl;
}