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/* Help friends in C++.

   Copyright (C) 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005,

   2007, 2008, 2010, 2011  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 3, 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 COPYING3.  If not see

<http://www.gnu.org/licenses/>.  */

#include "config.h"

#include "system.h"

#include "coretypes.h"

#include "tm.h"

#include "tree.h"

#include "cp-tree.h"

#include "flags.h"

#include "output.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 this_friend = TREE_VALUE (friends);

                  if (this_friend == NULL_TREE)

                    continue;

                  if (supplicant == this_friend)

                    return 1;

                  if (is_specialization_of_friend (supplicant, this_friend))

                    return 1;

                }

              break;

            }

        }

    }

  else

    /* It's a type.  */

    {

      if (same_type_p (supplicant, type))

        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_friend (TYPE_MAIN_DECL (supplicant), t) :

              same_type_p (supplicant, t))

            return 1;

        }

    }

  if (declp)

    {

      if (DECL_FUNCTION_MEMBER_P (supplicant))

        context = DECL_CONTEXT (supplicant);

      else

        context = NULL_TREE;

    }

  else

    {

      if (TYPE_CLASS_SCOPE_P (supplicant))

        /* Nested classes get the same access as their enclosing types, as

           per DR 45 (this is a change from the standard).  */

        context = TYPE_CONTEXT (supplicant);

      else

        /* Local classes have the same access as the enclosing function.  */

        context = decl_function_context (TYPE_MAIN_DECL (supplicant));

    }

  /* 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;

  tree ctx;

  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 (0, "%qD is already a friend of class %qT",

                             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);

    }

  ctx = DECL_CONTEXT (decl);

  if (ctx && CLASS_TYPE_P (ctx) && !uses_template_parms (ctx))

    perform_or_defer_access_check (TYPE_BINFO (ctx), 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;

  /* 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,

     defined inside the `if' block for TYPENAME_TYPE case, 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 class C<V>::D;

         };

       };

     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').

     The friend is a template friend iff FRIEND_DEPTH is nonzero.  */

  int class_template_depth = template_class_depth (type);

  int friend_depth = processing_template_decl - class_template_depth;

  if (! MAYBE_CLASS_TYPE_P (friend_type))

    {

      /* N1791: If the type specifier in a friend declaration designates a

         (possibly cv-qualified) class type, that class is declared as a

         friend; otherwise, the friend declaration is ignored.

         So don't complain in C++0x mode.  */

      if (cxx_dialect < cxx0x)

        pedwarn (input_location, complain ? 0 : OPT_pedantic,

                 "invalid type %qT declared %<friend%>", friend_type);

      return;

    }

  friend_type = cv_unqualified (friend_type);

  if (friend_depth)

    /* 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 %qT declared %<friend%>",

                 friend_type);

          return;

        }

    }

  else if (same_type_p (type, friend_type))

    {

      if (complain)

        warning (0, "class %qT is implicitly friends with itself",

                 type);

      return;

    }

  /* [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 (!friend_depth)

    ;/* ok */

  else if (TREE_CODE (friend_type) == TYPENAME_TYPE)

    {

      if (TREE_CODE (TYPENAME_TYPE_FULLNAME (friend_type))

          == TEMPLATE_ID_EXPR)

        {

          /* template <class U> friend class T::X<U>; */

          /* [temp.friend]

             Friend declarations shall not declare partial

             specializations.  */

          error ("partial specialization %qT declared %<friend%>",

                 friend_type);

          return;

        }

      else

        {

          /* We will figure this out later.  */

          bool template_member_p = false;

          tree ctype = TYPE_CONTEXT (friend_type);

          tree name = TYPE_IDENTIFIER (friend_type);

          tree decl;

          if (!uses_template_parms_level (ctype, class_template_depth

                                                 + friend_depth))

            template_member_p = true;

          if (class_template_depth)

            {

              /* We rely on tsubst_friend_class to check the

                 validity of the declaration later.  */

              if (template_member_p)

                friend_type

                  = make_unbound_class_template (ctype,

                                                 name,

                                                 current_template_parms,

                                                 tf_error);

              else

                friend_type

                  = make_typename_type (ctype, name, class_type, tf_error);

            }

          else

            {

              decl = lookup_member (ctype, name, 0, true, tf_warning_or_error);

              if (!decl)

                {

                  error ("%qT is not a member of %qT", name, ctype);

                  return;

                }

              if (template_member_p && !DECL_CLASS_TEMPLATE_P (decl))

                {

                  error ("%qT is not a member class template of %qT",

                         name, ctype);

                  error ("%q+D declared here", decl);

                  return;

                }

              if (!template_member_p && (TREE_CODE (decl) != TYPE_DECL

                                         || !CLASS_TYPE_P (TREE_TYPE (decl))))

                {

                  error ("%qT is not a nested class of %qT",

                         name, ctype);

                  error ("%q+D declared here", decl);

                  return;

                }

              friend_type = CLASSTYPE_TI_TEMPLATE (TREE_TYPE (decl));

            }

        }

    }

  else if (TREE_CODE (friend_type) == TEMPLATE_TYPE_PARM)

    {

      /* template <class T> friend class T; */

      error ("template parameter type %qT 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 ("%q#T is not a template", friend_type);

      return;

    }

  else

    /* template <class T> friend class A; where A is a template */

    friend_type = CLASSTYPE_TI_TEMPLATE (friend_type);

  if (friend_type == error_mark_node)

    return;

  /* 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 (0, "%qD is already a friend of %qT", probe, type);

              break;

            }

        }

      else if (TREE_CODE (probe) != TEMPLATE_DECL)

        {

          if (same_type_p (probe, friend_type))

            {

              if (complain)

                warning (0, "%qT is already a friend of %qT", 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 (TREE_CODE (friend_type) == TEMPLATE_DECL)

        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));

    }

}

/* Record DECL (a FUNCTION_DECL) as a friend of the

   CURRENT_CLASS_TYPE.  If DECL is a member function, CTYPE is the

   class of which it is a member, as named in the friend declaration.

   DECLARATOR is the name of the friend.  FUNCDEF_FLAG is true if the

   friend declaration is a definition of the function.  FLAGS is as

   for grokclass fn.  */

tree

do_friend (tree ctype, tree declarator, tree decl,

           tree attrlist, enum overload_flags flags,

           bool funcdef_flag)

{

  gcc_assert (TREE_CODE (decl) == FUNCTION_DECL);

  gcc_assert (!ctype || MAYBE_CLASS_TYPE_P (ctype));

  /* Every decl that gets here is a friend of something.  */

  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);

  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 (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;

      grokclassfn (ctype, decl, flags);

      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)

          || (CLASS_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=*/true);

          else

            decl = check_classfn (ctype, decl,

                                  template_member_p

                                  ? current_template_parms

                                  : NULL_TREE);

          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 %qD declared as friend before type %qT 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.  */

      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=*/true);

          else if (current_function_decl)

            {

              /* This must be a local class.  11.5p11:

                 If a friend declaration appears in a local class (9.8) and

                 the name specified is an unqualified name, a prior

                 declaration is looked up without considering scopes that

                 are outside the innermost enclosing non-class scope. For a

                 friend function declaration, if there is no prior

                 declaration, the program is ill-formed.  */

              tree t = lookup_name_innermost_nonclass_level (DECL_NAME (decl));

              if (t)

                decl = pushdecl_maybe_friend (decl, /*is_friend=*/true);

              else

                {

                  error ("friend declaration %qD in local class without "

                         "prior declaration", decl);

                  return error_mark_node;

                }

            }

          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, /*is_friend=*/true);

              pop_nested_namespace (ns);

            }

          if (warn)

            {

              static int explained;

              bool warned;

              warned = warning (OPT_Wnon_template_friend, "friend declaration "

                                "%q#D declares a non-template function", decl);

              if (! explained && warned)

                {

                  inform (input_location, "(if this is not what you intended, make sure "

                          "the function template has already been declared "

                          "and add <> after the function name here) ");

                  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;

    }

  return decl;

}