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 void
 133 add_friend (tree type, tree decl)
 134 {
 135   tree typedecl;
 136   tree list;
 137   tree name;
 138
 139   if (decl == error_mark_node)
 140     return;
 141
 142   typedecl = TYPE_MAIN_DECL (type);
 143   list = DECL_FRIENDLIST (typedecl);
 144   name = DECL_NAME (decl);
 145   type = TREE_TYPE (typedecl);
 146
 147   while (list)
 148     {
 149       if (name == FRIEND_NAME (list))
 150         {
 151           tree friends = FRIEND_DECLS (list);
 152           for (; friends ; friends = TREE_CHAIN (friends))
 153             {
 154               if (decl == TREE_VALUE (friends))
 155                 {
 156                   warning ("`%D' is already a friend of class `%T'",
 157                               decl, type);
 158                   cp_warning_at ("previous friend declaration of `%D'",
 159                                  TREE_VALUE (friends));
 160                   return;
 161                 }
 162             }
 163
 164           maybe_add_class_template_decl_list (type, decl, /*friend_p=*/1);
 165
 166           TREE_VALUE (list) = tree_cons (NULL_TREE, decl,
 167                                          TREE_VALUE (list));
 168           return;
 169         }
 170       list = TREE_CHAIN (list);
 171     }
 172
 173   maybe_add_class_template_decl_list (type, decl, /*friend_p=*/1);
 174
 175   DECL_FRIENDLIST (typedecl)
 176     = tree_cons (DECL_NAME (decl), build_tree_list (NULL_TREE, decl),
 177                  DECL_FRIENDLIST (typedecl));
 178   if (!uses_template_parms (type))
 179     DECL_BEFRIENDING_CLASSES (decl)
 180       = tree_cons (NULL_TREE, type,
 181                    DECL_BEFRIENDING_CLASSES (decl));
 182 }
 183
 184 /* Make FRIEND_TYPE a friend class to TYPE.  If FRIEND_TYPE has already
 185    been defined, we make all of its member functions friends of
 186    TYPE.  If not, we make it a pending friend, which can later be added
 187    when its definition is seen.  If a type is defined, then its TYPE_DECL's
 188    DECL_UNDEFINED_FRIENDS contains a (possibly empty) list of friend
 189    classes that are not defined.  If a type has not yet been defined,
 190    then the DECL_WAITING_FRIENDS contains a list of types
 191    waiting to make it their friend.  Note that these two can both
 192    be in use at the same time!  */
 193
 194 void
 195 make_friend_class (tree type, tree friend_type)
 196 {
 197   tree classes;
 198   int is_template_friend;
 199
 200   if (! IS_AGGR_TYPE (friend_type))
 201     {
 202       error ("invalid type `%T' declared `friend'", friend_type);
 203       return;
 204     }
 205
 206   if (processing_template_decl > template_class_depth (type))
 207     /* If the TYPE is a template then it makes sense for it to be
 208        friends with itself; this means that each instantiation is
 209        friends with all other instantiations.  */
 210     {
 211       if (CLASS_TYPE_P (friend_type)
 212           && CLASSTYPE_TEMPLATE_SPECIALIZATION (friend_type)
 213           && uses_template_parms (friend_type))
 214         {
 215           /* [temp.friend]
 216              Friend declarations shall not declare partial
 217              specializations.  */
 218           error ("partial specialization `%T' declared `friend'",
 219                  friend_type);
 220           return;
 221         }
 222
 223       is_template_friend = 1;
 224     }
 225   else if (same_type_p (type, friend_type))
 226     {
 227       pedwarn ("class `%T' is implicitly friends with itself",
 228                   type);
 229       return;
 230     }
 231   else
 232     is_template_friend = 0;
 233
 234   /* [temp.friend]
 235
 236      A friend of a class or class template can be a function or
 237      class template, a specialization of a function template or
 238      class template, or an ordinary (nontemplate) function or
 239      class.  */
 240   if (!is_template_friend)
 241     ;/* ok */
 242   else if (TREE_CODE (friend_type) == TYPENAME_TYPE)
 243     {
 244       /* template <class T> friend typename S<T>::X; */
 245       error ("typename type `%#T' declared `friend'", friend_type);
 246       return;
 247     }
 248   else if (TREE_CODE (friend_type) == TEMPLATE_TYPE_PARM)
 249     {
 250       /* template <class T> friend class T; */
 251       error ("template parameter type `%T' declared `friend'", friend_type);
 252       return;
 253     }
 254   else if (!CLASSTYPE_TEMPLATE_INFO (friend_type))
 255     {
 256       /* template <class T> friend class A; where A is not a template */
 257       error ("`%#T' is not a template", friend_type);
 258       return;
 259     }
 260
 261   if (is_template_friend)
 262     friend_type = CLASSTYPE_TI_TEMPLATE (friend_type);
 263
 264   /* See if it is already a friend.  */
 265   for (classes = CLASSTYPE_FRIEND_CLASSES (type);
 266        classes;
 267        classes = TREE_CHAIN (classes))
 268     {
 269       tree probe = TREE_VALUE (classes);
 270
 271       if (TREE_CODE (friend_type) == TEMPLATE_DECL)
 272         {
 273           if (friend_type == probe)
 274             {
 275               warning ("`%D' is already a friend of `%T'",
 276                        probe, type);
 277               break;
 278             }
 279         }
 280       else if (TREE_CODE (probe) != TEMPLATE_DECL)
 281         {
 282           if (same_type_p (probe, friend_type))
 283             {
 284               warning ("`%T' is already a friend of `%T'",
 285                        probe, type);
 286               break;
 287             }
 288         }
 289     }
 290
 291   if (!classes)
 292     {
 293       maybe_add_class_template_decl_list (type, friend_type, /*friend_p=*/1);
 294
 295       CLASSTYPE_FRIEND_CLASSES (type)
 296         = tree_cons (NULL_TREE, friend_type, CLASSTYPE_FRIEND_CLASSES (type));
 297       if (is_template_friend)
 298         friend_type = TREE_TYPE (friend_type);
 299       if (!uses_template_parms (type))
 300         CLASSTYPE_BEFRIENDING_CLASSES (friend_type)
 301           = tree_cons (NULL_TREE, type,
 302                        CLASSTYPE_BEFRIENDING_CLASSES (friend_type));
 303     }
 304 }
 305
 306 /* Main friend processor.
 307
 308    CTYPE is the class this friend belongs to.
 309
 310    DECLARATOR is the name of the friend.
 311
 312    DECL is the FUNCTION_DECL that the friend is.
 313
 314    In case we are parsing a friend which is part of an inline
 315    definition, we will need to store PARM_DECL chain that comes
 316    with it into the DECL_ARGUMENTS slot of the FUNCTION_DECL.
 317
 318    FLAGS is just used for `grokclassfn'.
 319
 320    QUALS say what special qualifies should apply to the object
 321    pointed to by `this'.  */
 322
 323 tree
 324 do_friend (tree ctype, tree declarator, tree decl, tree parmdecls,
 325            tree attrlist, enum overload_flags flags, tree quals,
 326            int funcdef_flag)
 327 {
 328   int is_friend_template = 0;
 329
 330   /* Every decl that gets here is a friend of something.  */
 331   DECL_FRIEND_P (decl) = 1;
 332
 333   if (TREE_CODE (declarator) == TEMPLATE_ID_EXPR)
 334     {
 335       declarator = TREE_OPERAND (declarator, 0);
 336       if (is_overloaded_fn (declarator))
 337         declarator = DECL_NAME (get_first_fn (declarator));
 338     }
 339
 340   if (TREE_CODE (decl) != FUNCTION_DECL)
 341     abort ();
 342
 343   is_friend_template = PROCESSING_REAL_TEMPLATE_DECL_P ();
 344
 345   if (ctype)
 346     {
 347       tree cname = TYPE_NAME (ctype);
 348       if (TREE_CODE (cname) == TYPE_DECL)
 349         cname = DECL_NAME (cname);
 350
 351       /* A method friend.  */
 352       if (flags == NO_SPECIAL && ctype && declarator == cname)
 353         DECL_CONSTRUCTOR_P (decl) = 1;
 354
 355       /* This will set up DECL_ARGUMENTS for us.  */
 356       grokclassfn (ctype, decl, flags, quals);
 357
 358       if (is_friend_template)
 359         decl = DECL_TI_TEMPLATE (push_template_decl (decl));
 360       else if (DECL_TEMPLATE_INFO (decl))
 361         ;
 362       else if (template_class_depth (current_class_type))
 363         decl = push_template_decl_real (decl, /*is_friend=*/1);
 364
 365       /* We can't do lookup in a type that involves template
 366          parameters.  Instead, we rely on tsubst_friend_function
 367          to check the validity of the declaration later.  */
 368       if (processing_template_decl)
 369         add_friend (current_class_type, decl);
 370       /* A nested class may declare a member of an enclosing class
 371          to be a friend, so we do lookup here even if CTYPE is in
 372          the process of being defined.  */
 373       else if (COMPLETE_TYPE_P (ctype) || TYPE_BEING_DEFINED (ctype))
 374         {
 375           decl = check_classfn (ctype, decl);
 376
 377           if (decl)
 378             add_friend (current_class_type, decl);
 379         }
 380       else
 381         error ("member `%D' declared as friend before type `%T' defined",
 382                   decl, ctype);
 383     }
 384   /* A global friend.
 385      @@ or possibly a friend from a base class ?!?  */
 386   else if (TREE_CODE (decl) == FUNCTION_DECL)
 387     {
 388       /* Friends must all go through the overload machinery,
 389          even though they may not technically be overloaded.
 390
 391          Note that because classes all wind up being top-level
 392          in their scope, their friend wind up in top-level scope as well.  */
 393       DECL_ARGUMENTS (decl) = parmdecls;
 394       if (funcdef_flag)
 395         SET_DECL_FRIEND_CONTEXT (decl, current_class_type);
 396
 397       if (! DECL_USE_TEMPLATE (decl))
 398         {
 399           /* We must check whether the decl refers to template
 400              arguments before push_template_decl_real adds a
 401              reference to the containing template class.  */
 402           int warn = (warn_nontemplate_friend
 403                       && ! funcdef_flag && ! is_friend_template
 404                       && current_template_parms
 405                       && uses_template_parms (decl));
 406
 407           if (is_friend_template
 408               || template_class_depth (current_class_type) != 0)
 409             /* We can't call pushdecl for a template class, since in
 410                general, such a declaration depends on template
 411                parameters.  Instead, we call pushdecl when the class
 412                is instantiated.  */
 413             decl = push_template_decl_real (decl, /*is_friend=*/1);
 414           else if (current_function_decl)
 415             /* This must be a local class, so pushdecl will be ok, and
 416                insert an unqualified friend into the local scope
 417                (rather than the containing namespace scope, which the
 418                next choice will do).  */
 419             decl = pushdecl (decl);
 420           else
 421             {
 422               /* We can't use pushdecl, as we might be in a template
 423                  class specialization, and pushdecl will insert an
 424                  unqualified friend decl into the template parameter
 425                  scope, rather than the namespace containing it.  */
 426               tree ns = decl_namespace_context (decl);
 427
 428               push_nested_namespace (ns);
 429               decl = pushdecl_namespace_level (decl);
 430               pop_nested_namespace (ns);
 431             }
 432
 433           if (warn)
 434             {
 435               static int explained;
 436               warning ("friend declaration `%#D' declares a non-template function", decl);
 437               if (! explained)
 438                 {
 439                   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");
 440                   explained = 1;
 441                 }
 442             }
 443         }
 444
 445       add_friend (current_class_type,
 446                   is_friend_template ? DECL_TI_TEMPLATE (decl) : decl);
 447       DECL_FRIEND_P (decl) = 1;
 448     }
 449
 450   /* Unfortunately, we have to handle attributes here.  Normally we would
 451      handle them in start_decl_1, but since this is a friend decl start_decl_1
 452      never gets to see it.  */
 453
 454   /* Set attributes here so if duplicate decl, will have proper attributes.  */
 455   cplus_decl_attributes (&decl, attrlist, 0);
 456
 457   return decl;
 458 }