gcc/cp/friend.c

   1 /* Help friends in C++.
   2    Copyright (C) 1997, 1998, 1999, 2000, 2001, 2002, 2003
   3    Free Software Foundation, Inc.
   4
   5 This file is part of GCC.
   6
   7 GCC is free software; you can redistribute it and/or modify
   8 it under the terms of the GNU General Public License as published by
   9 the Free Software Foundation; either version 2, or (at your option)
  10 any later version.
  11
  12 GCC is distributed in the hope that it will be useful,
  13 but WITHOUT ANY WARRANTY; without even the implied warranty of
  14 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15 GNU General Public License for more details.
  16
  17 You should have received a copy of the GNU General Public License
  18 along with GCC; see the file COPYING.  If not, write to
  19 the Free Software Foundation, 59 Temple Place - Suite 330,
  20 Boston, MA 02111-1307, USA.  */
  21
  22 #include "config.h"
  23 #include "system.h"
  24 #include "coretypes.h"
  25 #include "tm.h"
  26 #include "tree.h"
  27 #include "rtl.h"
  28 #include "expr.h"
  29 #include "cp-tree.h"
  30 #include "flags.h"
  31 #include "output.h"
  32 #include "toplev.h"
  33
  34 /* Friend data structures are described in cp-tree.h.  */
  35
  36 /* Returns nonzero if SUPPLICANT is a friend of TYPE.  */
  37
  38 int
  39 is_friend (tree type, tree supplicant)
  40 {
  41   int declp;
  42   register tree list;
  43   tree context;
  44
  45   if (supplicant == NULL_TREE || type == NULL_TREE)
  46     return 0;
  47
  48   declp = DECL_P (supplicant);
  49
  50   if (declp)
  51     /* It's a function decl.  */
  52     {
  53       tree list = DECL_FRIENDLIST (TYPE_MAIN_DECL (type));
  54       tree name = DECL_NAME (supplicant);
  55
  56       for (; list ; list = TREE_CHAIN (list))
  57         {
  58           if (name == FRIEND_NAME (list))
  59             {
  60               tree friends = FRIEND_DECLS (list);
  61               for (; friends ; friends = TREE_CHAIN (friends))
  62                 {
  63                   if (TREE_VALUE (friends) == NULL_TREE)
  64                     continue;
  65
  66                   if (supplicant == TREE_VALUE (friends))
  67                     return 1;
  68
  69                   /* Temporarily, we are more lenient to deal with
  70                      nested friend functions, for which there can be
  71                      more than one FUNCTION_DECL, despite being the
  72                      same function.  When that's fixed, this bit can
  73                      go.  */
  74                   if (DECL_FUNCTION_MEMBER_P (supplicant)
  75                       && same_type_p (TREE_TYPE (supplicant),
  76                                       TREE_TYPE (TREE_VALUE (friends))))
  77                     return 1;
  78
  79                   if (TREE_CODE (TREE_VALUE (friends)) == TEMPLATE_DECL
  80                       && is_specialization_of (supplicant,
  81                                                TREE_VALUE (friends)))
  82                     return 1;
  83                 }
  84               break;
  85             }
  86         }
  87     }
  88   else
  89     /* It's a type.  */
  90     {
  91       /* Nested classes are implicitly friends of their enclosing types, as
  92          per core issue 45 (this is a change from the standard).  */
  93       for (context = supplicant;
  94            context && TYPE_P (context);
  95            context = TYPE_CONTEXT (context))
  96         if (type == context)
  97           return 1;
  98
  99       list = CLASSTYPE_FRIEND_CLASSES (TREE_TYPE (TYPE_MAIN_DECL (type)));
 100       for (; list ; list = TREE_CHAIN (list))
 101         {
 102           tree t = TREE_VALUE (list);
 103
 104           if (TREE_CODE (t) == TEMPLATE_DECL ?
 105               is_specialization_of (TYPE_MAIN_DECL (supplicant), t) :
 106               same_type_p (supplicant, t))
 107             return 1;
 108         }
 109     }
 110
 111   if (declp && DECL_FUNCTION_MEMBER_P (supplicant))
 112     context = DECL_CONTEXT (supplicant);
 113   else if (! declp)
 114     /* Local classes have the same access as the enclosing function.  */
 115     context = decl_function_context (TYPE_MAIN_DECL (supplicant));
 116   else
 117     context = NULL_TREE;
 118
 119   /* A namespace is not friend to anybody.  */
 120   if (context && TREE_CODE (context) == NAMESPACE_DECL)
 121     context = NULL_TREE;
 122
 123   if (context)
 124     return is_friend (type, context);
 125
 126   return 0;
 127 }
 128
 129 /* Add a new friend to the friends of the aggregate type TYPE.
 130    DECL is the FUNCTION_DECL of the friend being added.
 131
 132    If COMPLAIN is true, warning about duplicate friend is issued.
 133    We want to have this diagnostics during parsing but not
 134    when a template is being instantiated.  */
 135
 136 void
 137 add_friend (tree type, tree decl, bool complain)
 138 {
 139   tree typedecl;
 140   tree list;
 141   tree name;
 142
 143   if (decl == error_mark_node)
 144     return;
 145
 146   typedecl = TYPE_MAIN_DECL (type);
 147   list = DECL_FRIENDLIST (typedecl);
 148   name = DECL_NAME (decl);
 149   type = TREE_TYPE (typedecl);
 150
 151   while (list)
 152     {
 153       if (name == FRIEND_NAME (list))
 154         {
 155           tree friends = FRIEND_DECLS (list);
 156           for (; friends ; friends = TREE_CHAIN (friends))
 157             {
 158               if (decl == TREE_VALUE (friends))
 159                 {
 160                   if (complain)
 161                     warning ("`%D' is already a friend of class `%T'",
 162                              decl, type);
 163                   return;
 164                 }
 165             }
 166
 167           maybe_add_class_template_decl_list (type, decl, /*friend_p=*/1);
 168
 169           TREE_VALUE (list) = tree_cons (NULL_TREE, decl,
 170                                          TREE_VALUE (list));
 171           return;
 172         }
 173       list = TREE_CHAIN (list);
 174     }
 175
 176   if (DECL_CLASS_SCOPE_P (decl))
 177     perform_or_defer_access_check (TYPE_BINFO (DECL_CONTEXT (decl)), decl);
 178
 179   maybe_add_class_template_decl_list (type, decl, /*friend_p=*/1);
 180
 181   DECL_FRIENDLIST (typedecl)
 182     = tree_cons (DECL_NAME (decl), build_tree_list (NULL_TREE, decl),
 183                  DECL_FRIENDLIST (typedecl));
 184   if (!uses_template_parms (type))
 185     DECL_BEFRIENDING_CLASSES (decl)
 186       = tree_cons (NULL_TREE, type,
 187                    DECL_BEFRIENDING_CLASSES (decl));
 188 }
 189
 190 /* Make FRIEND_TYPE a friend class to TYPE.  If FRIEND_TYPE has already
 191    been defined, we make all of its member functions friends of
 192    TYPE.  If not, we make it a pending friend, which can later be added
 193    when its definition is seen.  If a type is defined, then its TYPE_DECL's
 194    DECL_UNDEFINED_FRIENDS contains a (possibly empty) list of friend
 195    classes that are not defined.  If a type has not yet been defined,
 196    then the DECL_WAITING_FRIENDS contains a list of types
 197    waiting to make it their friend.  Note that these two can both
 198    be in use at the same time!
 199
 200    If COMPLAIN is true, warning about duplicate friend is issued.
 201    We want to have this diagnostics during parsing but not
 202    when a template is being instantiated.  */
 203
 204 void
 205 make_friend_class (tree type, tree friend_type, bool complain)
 206 {
 207   tree classes;
 208   int is_template_friend;
 209
 210   if (! IS_AGGR_TYPE (friend_type))
 211     {
 212       error ("invalid type `%T' declared `friend'", friend_type);
 213       return;
 214     }
 215
 216   if (processing_template_decl > template_class_depth (type))
 217     /* If the TYPE is a template then it makes sense for it to be
 218        friends with itself; this means that each instantiation is
 219        friends with all other instantiations.  */
 220     {
 221       if (CLASS_TYPE_P (friend_type)
 222           && CLASSTYPE_TEMPLATE_SPECIALIZATION (friend_type)
 223           && uses_template_parms (friend_type))
 224         {
 225           /* [temp.friend]
 226              Friend declarations shall not declare partial
 227              specializations.  */
 228           error ("partial specialization `%T' declared `friend'",
 229                  friend_type);
 230           return;
 231         }
 232
 233       is_template_friend = 1;
 234     }
 235   else if (same_type_p (type, friend_type))
 236     {
 237       if (complain)
 238         pedwarn ("class `%T' is implicitly friends with itself",
 239                  type);
 240       return;
 241     }
 242   else
 243     is_template_friend = 0;
 244
 245   /* [temp.friend]
 246
 247      A friend of a class or class template can be a function or
 248      class template, a specialization of a function template or
 249      class template, or an ordinary (nontemplate) function or
 250      class.  */
 251   if (!is_template_friend)
 252     ;/* ok */
 253   else if (TREE_CODE (friend_type) == TYPENAME_TYPE)
 254     {
 255       /* template <class T> friend typename S<T>::X; */
 256       error ("typename type `%#T' declared `friend'", friend_type);
 257       return;
 258     }
 259   else if (TREE_CODE (friend_type) == TEMPLATE_TYPE_PARM)
 260     {
 261       /* template <class T> friend class T; */
 262       error ("template parameter type `%T' declared `friend'", friend_type);
 263       return;
 264     }
 265   else if (!CLASSTYPE_TEMPLATE_INFO (friend_type))
 266     {
 267       /* template <class T> friend class A; where A is not a template */
 268       error ("`%#T' is not a template", friend_type);
 269       return;
 270     }
 271
 272   if (is_template_friend)
 273     friend_type = CLASSTYPE_TI_TEMPLATE (friend_type);
 274
 275   /* See if it is already a friend.  */
 276   for (classes = CLASSTYPE_FRIEND_CLASSES (type);
 277        classes;
 278        classes = TREE_CHAIN (classes))
 279     {
 280       tree probe = TREE_VALUE (classes);
 281
 282       if (TREE_CODE (friend_type) == TEMPLATE_DECL)
 283         {
 284           if (friend_type == probe)
 285             {
 286               if (complain)
 287                 warning ("`%D' is already a friend of `%T'",
 288                          probe, type);
 289               break;
 290             }
 291         }
 292       else if (TREE_CODE (probe) != TEMPLATE_DECL)
 293         {
 294           if (same_type_p (probe, friend_type))
 295             {
 296               if (complain)
 297                 warning ("`%T' is already a friend of `%T'",
 298                          probe, type);
 299               break;
 300             }
 301         }
 302     }
 303
 304   if (!classes)
 305     {
 306       maybe_add_class_template_decl_list (type, friend_type, /*friend_p=*/1);
 307
 308       CLASSTYPE_FRIEND_CLASSES (type)
 309         = tree_cons (NULL_TREE, friend_type, CLASSTYPE_FRIEND_CLASSES (type));
 310       if (is_template_friend)
 311         friend_type = TREE_TYPE (friend_type);
 312       if (!uses_template_parms (type))
 313         CLASSTYPE_BEFRIENDING_CLASSES (friend_type)
 314           = tree_cons (NULL_TREE, type,
 315                        CLASSTYPE_BEFRIENDING_CLASSES (friend_type));
 316     }
 317 }
 318
 319 /* Main friend processor.
 320
 321    CTYPE is the class this friend belongs to.
 322
 323    DECLARATOR is the name of the friend.
 324
 325    DECL is the FUNCTION_DECL that the friend is.
 326
 327    In case we are parsing a friend which is part of an inline
 328    definition, we will need to store PARM_DECL chain that comes
 329    with it into the DECL_ARGUMENTS slot of the FUNCTION_DECL.
 330
 331    FLAGS is just used for `grokclassfn'.
 332
 333    QUALS say what special qualifies should apply to the object
 334    pointed to by `this'.  */
 335
 336 tree
 337 do_friend (tree ctype, tree declarator, tree decl, tree parmdecls,
 338            tree attrlist, enum overload_flags flags, tree quals,
 339            int funcdef_flag)
 340 {
 341   int is_friend_template = 0;
 342
 343   /* Every decl that gets here is a friend of something.  */
 344   DECL_FRIEND_P (decl) = 1;
 345
 346   if (TREE_CODE (declarator) == TEMPLATE_ID_EXPR)
 347     {
 348       declarator = TREE_OPERAND (declarator, 0);
 349       if (is_overloaded_fn (declarator))
 350         declarator = DECL_NAME (get_first_fn (declarator));
 351     }
 352
 353   if (TREE_CODE (decl) != FUNCTION_DECL)
 354     abort ();
 355
 356   is_friend_template = PROCESSING_REAL_TEMPLATE_DECL_P ();
 357
 358   if (ctype)
 359     {
 360       tree cname = TYPE_NAME (ctype);
 361       if (TREE_CODE (cname) == TYPE_DECL)
 362         cname = DECL_NAME (cname);
 363
 364       /* A method friend.  */
 365       if (flags == NO_SPECIAL && ctype && declarator == cname)
 366         DECL_CONSTRUCTOR_P (decl) = 1;
 367
 368       /* This will set up DECL_ARGUMENTS for us.  */
 369       grokclassfn (ctype, decl, flags, quals);
 370
 371       if (is_friend_template)
 372         decl = DECL_TI_TEMPLATE (push_template_decl (decl));
 373       else if (DECL_TEMPLATE_INFO (decl))
 374         ;
 375       else if (template_class_depth (current_class_type))
 376         decl = push_template_decl_real (decl, /*is_friend=*/1);
 377
 378       /* We can't do lookup in a type that involves template
 379          parameters.  Instead, we rely on tsubst_friend_function
 380          to check the validity of the declaration later.  */
 381       if (processing_template_decl)
 382         add_friend (current_class_type, decl, /*complain=*/true);
 383       /* A nested class may declare a member of an enclosing class
 384          to be a friend, so we do lookup here even if CTYPE is in
 385          the process of being defined.  */
 386       else if (COMPLETE_TYPE_P (ctype) || TYPE_BEING_DEFINED (ctype))
 387         {
 388           decl = check_classfn (ctype, decl);
 389
 390           if (decl)
 391             add_friend (current_class_type, decl, /*complain=*/true);
 392         }
 393       else
 394         error ("member `%D' declared as friend before type `%T' defined",
 395                   decl, ctype);
 396     }
 397   /* A global friend.
 398      @@ or possibly a friend from a base class ?!?  */
 399   else if (TREE_CODE (decl) == FUNCTION_DECL)
 400     {
 401       /* Friends must all go through the overload machinery,
 402          even though they may not technically be overloaded.
 403
 404          Note that because classes all wind up being top-level
 405          in their scope, their friend wind up in top-level scope as well.  */
 406       DECL_ARGUMENTS (decl) = parmdecls;
 407       if (funcdef_flag)
 408         SET_DECL_FRIEND_CONTEXT (decl, current_class_type);
 409
 410       if (! DECL_USE_TEMPLATE (decl))
 411         {
 412           /* We must check whether the decl refers to template
 413              arguments before push_template_decl_real adds a
 414              reference to the containing template class.  */
 415           int warn = (warn_nontemplate_friend
 416                       && ! funcdef_flag && ! is_friend_template
 417                       && current_template_parms
 418                       && uses_template_parms (decl));
 419
 420           if (is_friend_template
 421               || template_class_depth (current_class_type) != 0)
 422             /* We can't call pushdecl for a template class, since in
 423                general, such a declaration depends on template
 424                parameters.  Instead, we call pushdecl when the class
 425                is instantiated.  */
 426             decl = push_template_decl_real (decl, /*is_friend=*/1);
 427           else if (current_function_decl)
 428             /* This must be a local class, so pushdecl will be ok, and
 429                insert an unqualified friend into the local scope
 430                (rather than the containing namespace scope, which the
 431                next choice will do).  */
 432             decl = pushdecl (decl);
 433           else
 434             {
 435               /* We can't use pushdecl, as we might be in a template
 436                  class specialization, and pushdecl will insert an
 437                  unqualified friend decl into the template parameter
 438                  scope, rather than the namespace containing it.  */
 439               tree ns = decl_namespace_context (decl);
 440
 441               push_nested_namespace (ns);
 442               decl = pushdecl_namespace_level (decl);
 443               pop_nested_namespace (ns);
 444             }
 445
 446           if (warn)
 447             {
 448               static int explained;
 449               warning ("friend declaration `%#D' declares a non-template function", decl);
 450               if (! explained)
 451                 {
 452                   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");
 453                   explained = 1;
 454                 }
 455             }
 456         }
 457
 458       add_friend (current_class_type,
 459                   is_friend_template ? DECL_TI_TEMPLATE (decl) : decl,
 460                   /*complain=*/true);
 461       DECL_FRIEND_P (decl) = 1;
 462     }
 463
 464   /* Unfortunately, we have to handle attributes here.  Normally we would
 465      handle them in start_decl_1, but since this is a friend decl start_decl_1
 466      never gets to see it.  */
 467
 468   /* Set attributes here so if duplicate decl, will have proper attributes.  */
 469   cplus_decl_attributes (&decl, attrlist, 0);
 470
 471   return decl;
 472 }