gcc/cp/friend.c

   1 /* Help friends in C++.
   2    Copyright (C) 1997 Free Software Foundation, Inc.
   3
   4 This file is part of GNU CC.
   5
   6 GNU CC is free software; you can redistribute it and/or modify
   7 it under the terms of the GNU General Public License as published by
   8 the Free Software Foundation; either version 2, or (at your option)
   9 any later version.
  10
  11 GNU CC is distributed in the hope that it will be useful,
  12 but WITHOUT ANY WARRANTY; without even the implied warranty of
  13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14 GNU General Public License for more details.
  15
  16 You should have received a copy of the GNU General Public License
  17 along with GNU CC; see the file COPYING.  If not, write to
  18 the Free Software Foundation, 59 Temple Place - Suite 330,
  19 Boston, MA 02111-1307, USA.  */
  20
  21 #include "config.h"
  22 #include "system.h"
  23 #include "tree.h"
  24 #include "rtl.h"
  25 #include "cp-tree.h"
  26 #include "flags.h"
  27 #include "output.h"
  28 #include "toplev.h"
  29
  30 static void add_friend PROTO((tree, tree));
  31 static void add_friends PROTO((tree, tree, tree));
  32
  33 /* Friend data structures are described in cp-tree.h.  */
  34
  35 int
  36 is_friend (type, supplicant)
  37      tree type, supplicant;
  38 {
  39   int declp;
  40   register tree list;
  41   tree context;
  42
  43   if (supplicant == NULL_TREE || type == NULL_TREE)
  44     return 0;
  45
  46   declp = (TREE_CODE_CLASS (TREE_CODE (supplicant)) == 'd');
  47
  48   if (declp)
  49     /* It's a function decl.  */
  50     {
  51       tree list = DECL_FRIENDLIST (TYPE_MAIN_DECL (type));
  52       tree name = DECL_NAME (supplicant);
  53       tree ctype;
  54
  55       if (DECL_FUNCTION_MEMBER_P (supplicant))
  56         ctype = DECL_CLASS_CONTEXT (supplicant);
  57       else
  58         ctype = NULL_TREE;
  59
  60       for (; list ; list = TREE_CHAIN (list))
  61         {
  62           if (name == TREE_PURPOSE (list))
  63             {
  64               tree friends = TREE_VALUE (list);
  65               for (; friends ; friends = TREE_CHAIN (friends))
  66                 {
  67                   if (comptypes (ctype, TREE_PURPOSE (friends), 1))
  68                     return 1;
  69
  70                   if (TREE_VALUE (friends) == NULL_TREE)
  71                     continue;
  72
  73                   if (supplicant == TREE_VALUE (friends))
  74                     return 1;
  75
  76                   /* With -fguiding-decls we are more lenient about
  77                      friendship.  This is bogus in general since two
  78                      specializations of a template with non-type
  79                      template parameters may have the same type, but
  80                      be different.
  81
  82                      Temporarily, we are also more lenient to deal
  83                      with nested friend functions, for which there can
  84                      be more than one FUNCTION_DECL, despite being the
  85                      same function.  When that's fixed, the
  86                      FUNCTION_MEMBER_P bit can go.  */
  87                   if ((flag_guiding_decls
  88                        || DECL_FUNCTION_MEMBER_P (supplicant))
  89                       && comptypes (TREE_TYPE (supplicant),
  90                                     TREE_TYPE (TREE_VALUE (friends)), 1))
  91                     return 1;
  92
  93                   if (TREE_CODE (TREE_VALUE (friends)) == TEMPLATE_DECL
  94                       && is_specialization_of (supplicant,
  95                                                TREE_VALUE (friends)))
  96                     return 1;
  97                 }
  98               break;
  99             }
 100         }
 101     }
 102   else
 103     /* It's a type.  */
 104     {
 105       if (type == supplicant)
 106         return 1;
 107
 108       list = CLASSTYPE_FRIEND_CLASSES (TREE_TYPE (TYPE_MAIN_DECL (type)));
 109       for (; list ; list = TREE_CHAIN (list))
 110         {
 111           tree t = TREE_VALUE (list);
 112
 113           if (TREE_CODE (t) == TEMPLATE_DECL ?
 114               is_specialization_of (TYPE_MAIN_DECL (supplicant), t) :
 115               comptypes (supplicant, t, 1))
 116             return 1;
 117         }
 118     }
 119
 120   if (declp && DECL_FUNCTION_MEMBER_P (supplicant))
 121     context = DECL_CLASS_CONTEXT (supplicant);
 122   else if (! declp)
 123     /* Local classes have the same access as the enclosing function.  */
 124     context = hack_decl_function_context (TYPE_MAIN_DECL (supplicant));
 125   else
 126     context = NULL_TREE;
 127
 128   /* A namespace is not friend to anybody. */
 129   if (context && TREE_CODE (context) == NAMESPACE_DECL)
 130     context = NULL_TREE;
 131
 132   if (context)
 133     return is_friend (type, context);
 134
 135   return 0;
 136 }
 137
 138 /* Add a new friend to the friends of the aggregate type TYPE.
 139    DECL is the FUNCTION_DECL of the friend being added.  */
 140
 141 static void
 142 add_friend (type, decl)
 143      tree type, decl;
 144 {
 145   tree typedecl = TYPE_MAIN_DECL (type);
 146   tree list = DECL_FRIENDLIST (typedecl);
 147   tree name = DECL_NAME (decl);
 148
 149   while (list)
 150     {
 151       if (name == TREE_PURPOSE (list))
 152         {
 153           tree friends = TREE_VALUE (list);
 154           for (; friends ; friends = TREE_CHAIN (friends))
 155             {
 156               if (decl == TREE_VALUE (friends))
 157                 {
 158                   cp_warning ("`%D' is already a friend of class `%T'",
 159                               decl, type);
 160                   cp_warning_at ("previous friend declaration of `%D'",
 161                                  TREE_VALUE (friends));
 162                   return;
 163                 }
 164             }
 165           TREE_VALUE (list) = tree_cons (error_mark_node, decl,
 166                                          TREE_VALUE (list));
 167           return;
 168         }
 169       list = TREE_CHAIN (list);
 170     }
 171   DECL_FRIENDLIST (typedecl)
 172     = tree_cons (DECL_NAME (decl), build_tree_list (error_mark_node, decl),
 173                  DECL_FRIENDLIST (typedecl));
 174   if (DECL_NAME (decl) == ansi_opname[(int) MODIFY_EXPR])
 175     {
 176       tree parmtypes = TYPE_ARG_TYPES (TREE_TYPE (decl));
 177       TYPE_HAS_ASSIGNMENT (TREE_TYPE (typedecl)) = 1;
 178       if (parmtypes && TREE_CHAIN (parmtypes))
 179         {
 180           tree parmtype = TREE_VALUE (TREE_CHAIN (parmtypes));
 181           if (TREE_CODE (parmtype) == REFERENCE_TYPE
 182               && TREE_TYPE (parmtypes) == TREE_TYPE (typedecl))
 183             TYPE_HAS_ASSIGN_REF (TREE_TYPE (typedecl)) = 1;
 184         }
 185     }
 186 }
 187
 188 /* Declare that every member function NAME in FRIEND_TYPE
 189    (which may be NULL_TREE) is a friend of type TYPE.  */
 190
 191 static void
 192 add_friends (type, name, friend_type)
 193      tree type, name, friend_type;
 194 {
 195   tree typedecl = TYPE_MAIN_DECL (type);
 196   tree list = DECL_FRIENDLIST (typedecl);
 197
 198   while (list)
 199     {
 200       if (name == TREE_PURPOSE (list))
 201         {
 202           tree friends = TREE_VALUE (list);
 203           while (friends && TREE_PURPOSE (friends) != friend_type)
 204             friends = TREE_CHAIN (friends);
 205           if (friends)
 206             {
 207               if (friend_type)
 208                 warning ("method `%s::%s' is already a friend of class",
 209                          TYPE_NAME_STRING (friend_type),
 210                          IDENTIFIER_POINTER (name));
 211               else
 212                 warning ("function `%s' is already a friend of class `%s'",
 213                          IDENTIFIER_POINTER (name),
 214                          IDENTIFIER_POINTER (DECL_NAME (typedecl)));
 215             }
 216           else
 217             TREE_VALUE (list) = tree_cons (friend_type, NULL_TREE,
 218                                            TREE_VALUE (list));
 219           return;
 220         }
 221       list = TREE_CHAIN (list);
 222     }
 223   DECL_FRIENDLIST (typedecl)
 224     = tree_cons (name,
 225                  build_tree_list (friend_type, NULL_TREE),
 226                  DECL_FRIENDLIST (typedecl));
 227   if (! strncmp (IDENTIFIER_POINTER (name),
 228                  IDENTIFIER_POINTER (ansi_opname[(int) MODIFY_EXPR]),
 229                  strlen (IDENTIFIER_POINTER (ansi_opname[(int) MODIFY_EXPR]))))
 230     {
 231       TYPE_HAS_ASSIGNMENT (TREE_TYPE (typedecl)) = 1;
 232       sorry ("declaring \"friend operator =\" will not find \"operator = (X&)\" if it exists");
 233     }
 234 }
 235
 236 /* Make FRIEND_TYPE a friend class to TYPE.  If FRIEND_TYPE has already
 237    been defined, we make all of its member functions friends of
 238    TYPE.  If not, we make it a pending friend, which can later be added
 239    when its definition is seen.  If a type is defined, then its TYPE_DECL's
 240    DECL_UNDEFINED_FRIENDS contains a (possibly empty) list of friend
 241    classes that are not defined.  If a type has not yet been defined,
 242    then the DECL_WAITING_FRIENDS contains a list of types
 243    waiting to make it their friend.  Note that these two can both
 244    be in use at the same time!  */
 245
 246 void
 247 make_friend_class (type, friend_type)
 248      tree type, friend_type;
 249 {
 250   tree classes;
 251   int is_template_friend;
 252
 253   if (IS_SIGNATURE (type))
 254     {
 255       error ("`friend' declaration in signature definition");
 256       return;
 257     }
 258   if (IS_SIGNATURE (friend_type))
 259     {
 260       error ("signature type `%s' declared `friend'",
 261              IDENTIFIER_POINTER (TYPE_IDENTIFIER (friend_type)));
 262       return;
 263     }
 264
 265   if (CLASSTYPE_TEMPLATE_SPECIALIZATION (friend_type)
 266       && uses_template_parms (friend_type))
 267     {
 268       /* [temp.friend]
 269
 270          Friend declarations shall not declare partial
 271          specializations.  */
 272       cp_error ("partial specialization `%T' declared `friend'",
 273                 friend_type);
 274       return;
 275     }
 276
 277   if (processing_template_decl > template_class_depth (type))
 278     /* If the TYPE is a template then it makes sense for it to be
 279        friends with itself; this means that each instantiation is
 280        friends with all other instantiations.  */
 281     is_template_friend = 1;
 282   else if (comptypes (type, friend_type, 1))
 283     {
 284       pedwarn ("class `%s' is implicitly friends with itself",
 285                TYPE_NAME_STRING (type));
 286       return;
 287     }
 288   else
 289     is_template_friend = 0;
 290
 291   GNU_xref_hier (type, friend_type, 0, 0, 1);
 292
 293   if (is_template_friend)
 294     friend_type = CLASSTYPE_TI_TEMPLATE (friend_type);
 295
 296   classes = CLASSTYPE_FRIEND_CLASSES (type);
 297   while (classes
 298          /* Stop if we find the same type on the list.  */
 299          && !(TREE_CODE (TREE_VALUE (classes)) == TEMPLATE_DECL ?
 300               friend_type == TREE_VALUE (classes) :
 301               comptypes (TREE_VALUE (classes), friend_type, 1)))
 302     classes = TREE_CHAIN (classes);
 303   if (classes)
 304     cp_warning ("`%T' is already a friend of `%T'",
 305                 TREE_VALUE (classes), type);
 306   else
 307     {
 308       CLASSTYPE_FRIEND_CLASSES (type)
 309         = tree_cons (NULL_TREE, friend_type, CLASSTYPE_FRIEND_CLASSES (type));
 310     }
 311 }
 312
 313 /* Main friend processor.  This is large, and for modularity purposes,
 314    has been removed from grokdeclarator.  It returns `void_type_node'
 315    to indicate that something happened, though a FIELD_DECL is
 316    not returned.
 317
 318    CTYPE is the class this friend belongs to.
 319
 320    DECLARATOR is the name of the friend.
 321
 322    DECL is the FUNCTION_DECL that the friend is.
 323
 324    In case we are parsing a friend which is part of an inline
 325    definition, we will need to store PARM_DECL chain that comes
 326    with it into the DECL_ARGUMENTS slot of the FUNCTION_DECL.
 327
 328    FLAGS is just used for `grokclassfn'.
 329
 330    QUALS say what special qualifies should apply to the object
 331    pointed to by `this'.  */
 332
 333 tree
 334 do_friend (ctype, declarator, decl, parmdecls, flags, quals, funcdef_flag)
 335      tree ctype, declarator, decl, parmdecls;
 336      enum overload_flags flags;
 337      tree quals;
 338      int funcdef_flag;
 339 {
 340   int is_friend_template = 0;
 341
 342   /* Every decl that gets here is a friend of something.  */
 343   DECL_FRIEND_P (decl) = 1;
 344
 345   if (TREE_CODE (declarator) == TEMPLATE_ID_EXPR)
 346     {
 347       declarator = TREE_OPERAND (declarator, 0);
 348       if (TREE_CODE (declarator) == LOOKUP_EXPR)
 349         declarator = TREE_OPERAND (declarator, 0);
 350       if (is_overloaded_fn (declarator))
 351         declarator = DECL_NAME (get_first_fn (declarator));
 352     }
 353
 354   if (TREE_CODE (decl) == FUNCTION_DECL)
 355     is_friend_template = PROCESSING_REAL_TEMPLATE_DECL_P ();
 356
 357   if (ctype)
 358     {
 359       tree cname = TYPE_NAME (ctype);
 360       if (TREE_CODE (cname) == TYPE_DECL)
 361         cname = DECL_NAME (cname);
 362
 363       /* A method friend.  */
 364       if (TREE_CODE (decl) == FUNCTION_DECL)
 365         {
 366           if (flags == NO_SPECIAL && ctype && declarator == cname)
 367             DECL_CONSTRUCTOR_P (decl) = 1;
 368
 369           /* This will set up DECL_ARGUMENTS for us.  */
 370           grokclassfn (ctype, decl, flags, quals);
 371
 372           if (is_friend_template)
 373             decl = DECL_TI_TEMPLATE (push_template_decl (decl));
 374
 375           /* A nested class may declare a member of an enclosing class
 376              to be a friend, so we do lookup here even if CTYPE is in
 377              the process of being defined.  */
 378           if (TYPE_SIZE (ctype) != 0 || TYPE_BEING_DEFINED (ctype))
 379             {
 380               /* But, we defer looup in template specializations until
 381                  they are fully specialized.  */
 382               if (template_class_depth (ctype) == 0)
 383                 decl = check_classfn (ctype, decl);
 384
 385               if (decl)
 386                 add_friend (current_class_type, decl);
 387             }
 388           else
 389             cp_error ("member `%D' declared as friend before type `%T' defined",
 390                       decl, ctype);
 391         }
 392       else
 393         {
 394           /* Possibly a bunch of method friends.  */
 395
 396           /* Get the class they belong to.  */
 397           tree ctype = IDENTIFIER_TYPE_VALUE (cname);
 398           tree fields = lookup_fnfields (TYPE_BINFO (ctype), declarator, 0);
 399
 400           if (fields)
 401             add_friends (current_class_type, declarator, ctype);
 402           else
 403             cp_error ("method `%D' is not a member of class `%T'",
 404                       declarator, ctype);
 405           decl = void_type_node;
 406         }
 407     }
 408   else if (TREE_CODE (decl) == FUNCTION_DECL
 409            && (MAIN_NAME_P (declarator)
 410                || (IDENTIFIER_LENGTH (declarator) > 10
 411                    && IDENTIFIER_POINTER (declarator)[0] == '_'
 412                    && IDENTIFIER_POINTER (declarator)[1] == '_'
 413                    && strncmp (IDENTIFIER_POINTER (declarator)+2,
 414                                "builtin_", 8) == 0)))
 415     {
 416       /* raw "main", and builtin functions never gets overloaded,
 417          but they can become friends.  */
 418       add_friend (current_class_type, decl);
 419       DECL_FRIEND_P (decl) = 1;
 420       decl = void_type_node;
 421     }
 422   /* A global friend.
 423      @@ or possibly a friend from a base class ?!?  */
 424   else if (TREE_CODE (decl) == FUNCTION_DECL)
 425     {
 426       /* Friends must all go through the overload machinery,
 427          even though they may not technically be overloaded.
 428
 429          Note that because classes all wind up being top-level
 430          in their scope, their friend wind up in top-level scope as well.  */
 431       set_mangled_name_for_decl (decl);
 432       DECL_ARGUMENTS (decl) = parmdecls;
 433       if (funcdef_flag)
 434         DECL_CLASS_CONTEXT (decl) = current_class_type;
 435
 436       if (! DECL_USE_TEMPLATE (decl))
 437         {
 438           /* We can call pushdecl here, because the TREE_CHAIN of this
 439              FUNCTION_DECL is not needed for other purposes.  Don't do
 440              this for a template instantiation.  However, we don't
 441              call pushdecl() for a friend function of a template
 442              class, since in general, such a declaration depends on
 443              template parameters.  Instead, we call pushdecl when the
 444              class is instantiated.  */
 445           if (!is_friend_template
 446               && template_class_depth (current_class_type) == 0)
 447             decl = pushdecl (decl);
 448           else
 449             decl = push_template_decl_real (decl, /*is_friend=*/1);
 450
 451           if (warn_nontemplate_friend
 452               && ! funcdef_flag && ! flag_guiding_decls && ! is_friend_template
 453               && current_template_parms && uses_template_parms (decl))
 454             {
 455               static int explained;
 456               cp_warning ("friend declaration `%#D'", decl);
 457               warning ("  declares a non-template function");
 458               if (! explained)
 459                 {
 460                   warning ("  (if this is not what you intended, make sure");
 461                   warning ("  the function template has already been declared,");
 462                   warning ("  and add <> after the function name here)");
 463                   warning ("  -Wno-non-template-friend disables this warning.");
 464                   explained = 1;
 465                 }
 466             }
 467         }
 468
 469       make_decl_rtl (decl, NULL_PTR, 1);
 470       add_friend (current_class_type,
 471                   is_friend_template ? DECL_TI_TEMPLATE (decl) : decl);
 472       DECL_FRIEND_P (decl) = 1;
 473     }
 474   else
 475     {
 476       /* @@ Should be able to ingest later definitions of this function
 477          before use.  */
 478       tree decl = lookup_name_nonclass (declarator);
 479       if (decl == NULL_TREE)
 480         {
 481           cp_warning ("implicitly declaring `%T' as struct", declarator);
 482           decl = xref_tag (record_type_node, declarator, 1);
 483           decl = TYPE_MAIN_DECL (decl);
 484         }
 485
 486       /* Allow abbreviated declarations of overloaded functions,
 487          but not if those functions are really class names.  */
 488       if (TREE_CODE (decl) == TREE_LIST && TREE_TYPE (TREE_PURPOSE (decl)))
 489         {
 490           cp_warning ("`friend %T' archaic, use `friend class %T' instead",
 491                       declarator, declarator);
 492           decl = TREE_TYPE (TREE_PURPOSE (decl));
 493         }
 494
 495       if (TREE_CODE (decl) == TREE_LIST)
 496         add_friends (current_class_type, TREE_PURPOSE (decl), NULL_TREE);
 497       else
 498         make_friend_class (current_class_type, TREE_TYPE (decl));
 499       decl = void_type_node;
 500     }
 501   return decl;
 502 }