gcc/cp/friend.c

   1 /* Help friends in C++.
   2    Copyright (C) 1997, 1998, 1999 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 (same_type_p (ctype, TREE_PURPOSE (friends)))
  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                       && same_type_p (TREE_TYPE (supplicant),
  90                                       TREE_TYPE (TREE_VALUE (friends))))
  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               same_type_p (supplicant, t))
 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) || ! IS_AGGR_TYPE (friend_type))
 259     {
 260       cp_error ("invalid type `%T' declared `friend'", friend_type);
 261       return;
 262     }
 263
 264   if (CLASSTYPE_TEMPLATE_SPECIALIZATION (friend_type)
 265       && uses_template_parms (friend_type))
 266     {
 267       /* [temp.friend]
 268
 269          Friend declarations shall not declare partial
 270          specializations.  */
 271       cp_error ("partial specialization `%T' declared `friend'",
 272                 friend_type);
 273       return;
 274     }
 275
 276   if (processing_template_decl > template_class_depth (type))
 277     /* If the TYPE is a template then it makes sense for it to be
 278        friends with itself; this means that each instantiation is
 279        friends with all other instantiations.  */
 280     is_template_friend = 1;
 281   else if (same_type_p (type, friend_type))
 282     {
 283       pedwarn ("class `%s' is implicitly friends with itself",
 284                TYPE_NAME_STRING (type));
 285       return;
 286     }
 287   else
 288     is_template_friend = 0;
 289
 290   GNU_xref_hier (type, friend_type, 0, 0, 1);
 291
 292   if (is_template_friend)
 293     friend_type = CLASSTYPE_TI_TEMPLATE (friend_type);
 294
 295   classes = CLASSTYPE_FRIEND_CLASSES (type);
 296   while (classes
 297          /* Stop if we find the same type on the list.  */
 298          && !(TREE_CODE (TREE_VALUE (classes)) == TEMPLATE_DECL ?
 299               friend_type == TREE_VALUE (classes) :
 300               same_type_p (TREE_VALUE (classes), friend_type)))
 301     classes = TREE_CHAIN (classes);
 302   if (classes)
 303     cp_warning ("`%T' is already a friend of `%T'",
 304                 TREE_VALUE (classes), type);
 305   else
 306     {
 307       CLASSTYPE_FRIEND_CLASSES (type)
 308         = tree_cons (NULL_TREE, friend_type, CLASSTYPE_FRIEND_CLASSES (type));
 309     }
 310 }
 311
 312 /* Main friend processor.  This is large, and for modularity purposes,
 313    has been removed from grokdeclarator.  It returns `void_type_node'
 314    to indicate that something happened, though a FIELD_DECL is
 315    not returned.
 316
 317    CTYPE is the class this friend belongs to.
 318
 319    DECLARATOR is the name of the friend.
 320
 321    DECL is the FUNCTION_DECL that the friend is.
 322
 323    In case we are parsing a friend which is part of an inline
 324    definition, we will need to store PARM_DECL chain that comes
 325    with it into the DECL_ARGUMENTS slot of the FUNCTION_DECL.
 326
 327    FLAGS is just used for `grokclassfn'.
 328
 329    QUALS say what special qualifies should apply to the object
 330    pointed to by `this'.  */
 331
 332 tree
 333 do_friend (ctype, declarator, decl, parmdecls, flags, quals, funcdef_flag)
 334      tree ctype, declarator, decl, parmdecls;
 335      enum overload_flags flags;
 336      tree quals;
 337      int funcdef_flag;
 338 {
 339   int is_friend_template = 0;
 340
 341   /* Every decl that gets here is a friend of something.  */
 342   DECL_FRIEND_P (decl) = 1;
 343
 344   if (TREE_CODE (declarator) == TEMPLATE_ID_EXPR)
 345     {
 346       declarator = TREE_OPERAND (declarator, 0);
 347       if (TREE_CODE (declarator) == LOOKUP_EXPR)
 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     is_friend_template = PROCESSING_REAL_TEMPLATE_DECL_P ();
 355
 356   if (ctype)
 357     {
 358       tree cname = TYPE_NAME (ctype);
 359       if (TREE_CODE (cname) == TYPE_DECL)
 360         cname = DECL_NAME (cname);
 361
 362       /* A method friend.  */
 363       if (TREE_CODE (decl) == FUNCTION_DECL)
 364         {
 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 (template_class_depth (current_class_type))
 374             decl = push_template_decl_real (decl, /*is_friend=*/1);
 375
 376           /* We can't do lookup in a type that involves template
 377              parameters.  Instead, we rely on tsubst_friend_function
 378              to check the validity of the declaration later.  */
 379           if (uses_template_parms (ctype))
 380             add_friend (current_class_type, decl);
 381           /* A nested class may declare a member of an enclosing class
 382              to be a friend, so we do lookup here even if CTYPE is in
 383              the process of being defined.  */
 384           else if (TYPE_SIZE (ctype) != 0 || TYPE_BEING_DEFINED (ctype))
 385             {
 386               decl = check_classfn (ctype, decl);
 387
 388               if (decl)
 389                 add_friend (current_class_type, decl);
 390             }
 391           else
 392             cp_error ("member `%D' declared as friend before type `%T' defined",
 393                       decl, ctype);
 394         }
 395       else
 396         {
 397           /* Possibly a bunch of method friends.  */
 398
 399           /* Get the class they belong to.  */
 400           tree ctype = IDENTIFIER_TYPE_VALUE (cname);
 401           tree fields = lookup_fnfields (TYPE_BINFO (ctype), declarator, 0);
 402
 403           if (fields)
 404             add_friends (current_class_type, declarator, ctype);
 405           else
 406             cp_error ("method `%D' is not a member of class `%T'",
 407                       declarator, ctype);
 408           decl = void_type_node;
 409         }
 410     }
 411   /* A global friend.
 412      @@ or possibly a friend from a base class ?!?  */
 413   else if (TREE_CODE (decl) == FUNCTION_DECL)
 414     {
 415       /* Friends must all go through the overload machinery,
 416          even though they may not technically be overloaded.
 417
 418          Note that because classes all wind up being top-level
 419          in their scope, their friend wind up in top-level scope as well.  */
 420       DECL_ARGUMENTS (decl) = parmdecls;
 421       if (funcdef_flag)
 422         DECL_CLASS_CONTEXT (decl) = current_class_type;
 423
 424       if (! DECL_USE_TEMPLATE (decl))
 425         {
 426           /* We can call pushdecl here, because the TREE_CHAIN of this
 427              FUNCTION_DECL is not needed for other purposes.  Don't do
 428              this for a template instantiation.  However, we don't
 429              call pushdecl() for a friend function of a template
 430              class, since in general, such a declaration depends on
 431              template parameters.  Instead, we call pushdecl when the
 432              class is instantiated.  */
 433           if (!is_friend_template
 434               && template_class_depth (current_class_type) == 0)
 435             decl = pushdecl (decl);
 436           else
 437             decl = push_template_decl_real (decl, /*is_friend=*/1);
 438
 439           if (warn_nontemplate_friend
 440               && ! funcdef_flag && ! flag_guiding_decls && ! is_friend_template
 441               && current_template_parms && uses_template_parms (decl))
 442             {
 443               static int explained;
 444               cp_warning ("friend declaration `%#D'", decl);
 445               warning ("  declares a non-template function");
 446               if (! explained)
 447                 {
 448                   warning ("  (if this is not what you intended, make sure");
 449                   warning ("  the function template has already been declared,");
 450                   warning ("  and add <> after the function name here)");
 451                   warning ("  -Wno-non-template-friend disables this warning.");
 452                   explained = 1;
 453                 }
 454             }
 455         }
 456
 457       make_decl_rtl (decl, NULL_PTR, 1);
 458       add_friend (current_class_type,
 459                   is_friend_template ? DECL_TI_TEMPLATE (decl) : decl);
 460       DECL_FRIEND_P (decl) = 1;
 461     }
 462   else
 463     {
 464       /* @@ Should be able to ingest later definitions of this function
 465          before use.  */
 466       tree decl = lookup_name_nonclass (declarator);
 467       if (decl == NULL_TREE)
 468         {
 469           cp_warning ("implicitly declaring `%T' as struct", declarator);
 470           decl = xref_tag (record_type_node, declarator, 1);
 471           decl = TYPE_MAIN_DECL (decl);
 472         }
 473
 474       /* Allow abbreviated declarations of overloaded functions,
 475          but not if those functions are really class names.  */
 476       if (TREE_CODE (decl) == TREE_LIST && TREE_TYPE (TREE_PURPOSE (decl)))
 477         {
 478           cp_warning ("`friend %T' archaic, use `friend class %T' instead",
 479                       declarator, declarator);
 480           decl = TREE_TYPE (TREE_PURPOSE (decl));
 481         }
 482
 483       if (TREE_CODE (decl) == TREE_LIST)
 484         add_friends (current_class_type, TREE_PURPOSE (decl), NULL_TREE);
 485       else
 486         make_friend_class (current_class_type, TREE_TYPE (decl));
 487       decl = void_type_node;
 488     }
 489   return decl;
 490 }