gcc/cp/friend.c

   1 /* Help friends in C++.
   2    Copyright (C) 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004
   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   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                   tree friend = TREE_VALUE (friends);
  64
  65                   if (friend == NULL_TREE)
  66                     continue;
  67
  68                   if (supplicant == friend)
  69                     return 1;
  70
  71                   if (is_specialization_of_friend (supplicant, friend))
  72                     return 1;
  73                 }
  74               break;
  75             }
  76         }
  77     }
  78   else
  79     /* It's a type.  */
  80     {
  81       /* Nested classes are implicitly friends of their enclosing types, as
  82          per core issue 45 (this is a change from the standard).  */
  83       for (context = supplicant;
  84            context && TYPE_P (context);
  85            context = TYPE_CONTEXT (context))
  86         if (type == context)
  87           return 1;
  88
  89       list = CLASSTYPE_FRIEND_CLASSES (TREE_TYPE (TYPE_MAIN_DECL (type)));
  90       for (; list ; list = TREE_CHAIN (list))
  91         {
  92           tree t = TREE_VALUE (list);
  93
  94           if (TREE_CODE (t) == TEMPLATE_DECL ?
  95               is_specialization_of (TYPE_MAIN_DECL (supplicant), t) :
  96               same_type_p (supplicant, t))
  97             return 1;
  98         }
  99     }
 100
 101   if (declp && DECL_FUNCTION_MEMBER_P (supplicant))
 102     context = DECL_CONTEXT (supplicant);
 103   else if (! declp)
 104     /* Local classes have the same access as the enclosing function.  */
 105     context = decl_function_context (TYPE_MAIN_DECL (supplicant));
 106   else
 107     context = NULL_TREE;
 108
 109   /* A namespace is not friend to anybody.  */
 110   if (context && TREE_CODE (context) == NAMESPACE_DECL)
 111     context = NULL_TREE;
 112
 113   if (context)
 114     return is_friend (type, context);
 115
 116   return 0;
 117 }
 118
 119 /* Add a new friend to the friends of the aggregate type TYPE.
 120    DECL is the FUNCTION_DECL of the friend being added.
 121
 122    If COMPLAIN is true, warning about duplicate friend is issued.
 123    We want to have this diagnostics during parsing but not
 124    when a template is being instantiated.  */
 125
 126 void
 127 add_friend (tree type, tree decl, bool complain)
 128 {
 129   tree typedecl;
 130   tree list;
 131   tree name;
 132   tree ctx;
 133
 134   if (decl == error_mark_node)
 135     return;
 136
 137   typedecl = TYPE_MAIN_DECL (type);
 138   list = DECL_FRIENDLIST (typedecl);
 139   name = DECL_NAME (decl);
 140   type = TREE_TYPE (typedecl);
 141
 142   while (list)
 143     {
 144       if (name == FRIEND_NAME (list))
 145         {
 146           tree friends = FRIEND_DECLS (list);
 147           for (; friends ; friends = TREE_CHAIN (friends))
 148             {
 149               if (decl == TREE_VALUE (friends))
 150                 {
 151                   if (complain)
 152                     warning ("`%D' is already a friend of class `%T'",
 153                              decl, type);
 154                   return;
 155                 }
 156             }
 157
 158           maybe_add_class_template_decl_list (type, decl, /*friend_p=*/1);
 159
 160           TREE_VALUE (list) = tree_cons (NULL_TREE, decl,
 161                                          TREE_VALUE (list));
 162           return;
 163         }
 164       list = TREE_CHAIN (list);
 165     }
 166
 167   ctx = DECL_CONTEXT (decl);
 168   if (ctx && CLASS_TYPE_P (ctx) && !uses_template_parms (ctx))
 169     perform_or_defer_access_check (TYPE_BINFO (ctx), decl);
 170
 171   maybe_add_class_template_decl_list (type, decl, /*friend_p=*/1);
 172
 173   DECL_FRIENDLIST (typedecl)
 174     = tree_cons (DECL_NAME (decl), build_tree_list (NULL_TREE, decl),
 175                  DECL_FRIENDLIST (typedecl));
 176   if (!uses_template_parms (type))
 177     DECL_BEFRIENDING_CLASSES (decl)
 178       = tree_cons (NULL_TREE, type,
 179                    DECL_BEFRIENDING_CLASSES (decl));
 180 }
 181
 182 /* Make FRIEND_TYPE a friend class to TYPE.  If FRIEND_TYPE has already
 183    been defined, we make all of its member functions friends of
 184    TYPE.  If not, we make it a pending friend, which can later be added
 185    when its definition is seen.  If a type is defined, then its TYPE_DECL's
 186    DECL_UNDEFINED_FRIENDS contains a (possibly empty) list of friend
 187    classes that are not defined.  If a type has not yet been defined,
 188    then the DECL_WAITING_FRIENDS contains a list of types
 189    waiting to make it their friend.  Note that these two can both
 190    be in use at the same time!
 191
 192    If COMPLAIN is true, warning about duplicate friend is issued.
 193    We want to have this diagnostics during parsing but not
 194    when a template is being instantiated.  */
 195
 196 void
 197 make_friend_class (tree type, tree friend_type, bool complain)
 198 {
 199   tree classes;
 200   int is_template_friend;
 201
 202   if (! IS_AGGR_TYPE (friend_type))
 203     {
 204       error ("invalid type `%T' declared `friend'", friend_type);
 205       return;
 206     }
 207
 208   if (processing_template_decl > template_class_depth (type))
 209     /* If the TYPE is a template then it makes sense for it to be
 210        friends with itself; this means that each instantiation is
 211        friends with all other instantiations.  */
 212     {
 213       if (CLASS_TYPE_P (friend_type)
 214           && CLASSTYPE_TEMPLATE_SPECIALIZATION (friend_type)
 215           && uses_template_parms (friend_type))
 216         {
 217           /* [temp.friend]
 218              Friend declarations shall not declare partial
 219              specializations.  */
 220           error ("partial specialization `%T' declared `friend'",
 221                  friend_type);
 222           return;
 223         }
 224
 225       is_template_friend = 1;
 226     }
 227   else if (same_type_p (type, friend_type))
 228     {
 229       if (complain)
 230         pedwarn ("class `%T' is implicitly friends with itself",
 231                  type);
 232       return;
 233     }
 234   else
 235     is_template_friend = 0;
 236
 237   /* [temp.friend]
 238
 239      A friend of a class or class template can be a function or
 240      class template, a specialization of a function template or
 241      class template, or an ordinary (nontemplate) function or
 242      class.  */
 243   if (!is_template_friend)
 244     ;/* ok */
 245   else if (TREE_CODE (friend_type) == TYPENAME_TYPE)
 246     {
 247       /* template <class T> friend typename S<T>::X; */
 248       error ("typename type `%#T' declared `friend'", friend_type);
 249       return;
 250     }
 251   else if (TREE_CODE (friend_type) == TEMPLATE_TYPE_PARM)
 252     {
 253       /* template <class T> friend class T; */
 254       error ("template parameter type `%T' declared `friend'", friend_type);
 255       return;
 256     }
 257   else if (!CLASSTYPE_TEMPLATE_INFO (friend_type))
 258     {
 259       /* template <class T> friend class A; where A is not a template */
 260       error ("`%#T' is not a template", friend_type);
 261       return;
 262     }
 263
 264   if (is_template_friend)
 265     friend_type = CLASSTYPE_TI_TEMPLATE (friend_type);
 266
 267   /* See if it is already a friend.  */
 268   for (classes = CLASSTYPE_FRIEND_CLASSES (type);
 269        classes;
 270        classes = TREE_CHAIN (classes))
 271     {
 272       tree probe = TREE_VALUE (classes);
 273
 274       if (TREE_CODE (friend_type) == TEMPLATE_DECL)
 275         {
 276           if (friend_type == probe)
 277             {
 278               if (complain)
 279                 warning ("`%D' is already a friend of `%T'",
 280                          probe, type);
 281               break;
 282             }
 283         }
 284       else if (TREE_CODE (probe) != TEMPLATE_DECL)
 285         {
 286           if (same_type_p (probe, friend_type))
 287             {
 288               if (complain)
 289                 warning ("`%T' is already a friend of `%T'",
 290                          probe, type);
 291               break;
 292             }
 293         }
 294     }
 295
 296   if (!classes)
 297     {
 298       maybe_add_class_template_decl_list (type, friend_type, /*friend_p=*/1);
 299
 300       CLASSTYPE_FRIEND_CLASSES (type)
 301         = tree_cons (NULL_TREE, friend_type, CLASSTYPE_FRIEND_CLASSES (type));
 302       if (is_template_friend)
 303         friend_type = TREE_TYPE (friend_type);
 304       if (!uses_template_parms (type))
 305         CLASSTYPE_BEFRIENDING_CLASSES (friend_type)
 306           = tree_cons (NULL_TREE, type,
 307                        CLASSTYPE_BEFRIENDING_CLASSES (friend_type));
 308     }
 309 }
 310
 311 /* Main friend processor.
 312
 313    CTYPE is the class this friend belongs to.
 314
 315    DECLARATOR is the name of the friend.
 316
 317    DECL is the FUNCTION_DECL that the friend is.
 318
 319    FLAGS is just used for `grokclassfn'.
 320
 321    QUALS say what special qualifies should apply to the object
 322    pointed to by `this'.  */
 323
 324 tree
 325 do_friend (tree ctype, tree declarator, tree decl,
 326            tree attrlist, enum overload_flags flags,
 327            cp_cv_quals quals,
 328            int funcdef_flag)
 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   if (ctype)
 344     {
 345       /* CLASS_TEMPLATE_DEPTH counts the number of template headers for
 346          the enclosing class.  FRIEND_DEPTH counts the number of template
 347          headers used for this friend declaration.  TEMPLATE_MEMBER_P is
 348          true if a template header in FRIEND_DEPTH is intended for
 349          DECLARATOR.  For example, the code
 350
 351            template <class T> struct A {
 352              template <class U> struct B {
 353                template <class V> template <class W>
 354                  friend void C<V>::f(W);
 355              };
 356            };
 357
 358          will eventually give the following results
 359
 360          1. CLASS_TEMPLATE_DEPTH equals 2 (for `T' and `U').
 361          2. FRIEND_DEPTH equals 2 (for `V' and `W').
 362          3. TEMPLATE_MEMBER_P is true (for `W').  */
 363
 364       int class_template_depth = template_class_depth (current_class_type);
 365       int friend_depth = processing_template_decl - class_template_depth;
 366       /* We will figure this out later.  */
 367       bool template_member_p = false;
 368
 369       tree cname = TYPE_NAME (ctype);
 370       if (TREE_CODE (cname) == TYPE_DECL)
 371         cname = DECL_NAME (cname);
 372
 373       /* A method friend.  */
 374       if (flags == NO_SPECIAL && declarator == cname)
 375         DECL_CONSTRUCTOR_P (decl) = 1;
 376
 377       /* This will set up DECL_ARGUMENTS for us.  */
 378       grokclassfn (ctype, decl, flags, quals);
 379
 380       if (friend_depth)
 381         {
 382           if (!uses_template_parms_level (ctype, class_template_depth
 383                                                  + friend_depth))
 384             template_member_p = true;
 385         }
 386
 387       /* A nested class may declare a member of an enclosing class
 388          to be a friend, so we do lookup here even if CTYPE is in
 389          the process of being defined.  */
 390       if (class_template_depth
 391           || COMPLETE_TYPE_P (ctype)
 392           || TYPE_BEING_DEFINED (ctype))
 393         {
 394           if (DECL_TEMPLATE_INFO (decl))
 395             /* DECL is a template specialization.  No need to
 396                build a new TEMPLATE_DECL.  */
 397             ;
 398           else if (class_template_depth)
 399             /* We rely on tsubst_friend_function to check the
 400                validity of the declaration later.  */
 401             decl = push_template_decl_real (decl, /*is_friend=*/1);
 402           else
 403             decl = check_classfn (ctype, decl,
 404                                   template_member_p
 405                                   ? current_template_parms
 406                                   : NULL_TREE);
 407
 408           if (template_member_p && decl && TREE_CODE (decl) == FUNCTION_DECL)
 409             decl = DECL_TI_TEMPLATE (decl);
 410
 411           if (decl)
 412             add_friend (current_class_type, decl, /*complain=*/true);
 413         }
 414       else
 415         error ("member `%D' declared as friend before type `%T' defined",
 416                   decl, ctype);
 417     }
 418   /* A global friend.
 419      @@ or possibly a friend from a base class ?!?  */
 420   else if (TREE_CODE (decl) == FUNCTION_DECL)
 421     {
 422       int is_friend_template = PROCESSING_REAL_TEMPLATE_DECL_P ();
 423
 424       /* Friends must all go through the overload machinery,
 425          even though they may not technically be overloaded.
 426
 427          Note that because classes all wind up being top-level
 428          in their scope, their friend wind up in top-level scope as well.  */
 429       if (funcdef_flag)
 430         SET_DECL_FRIEND_CONTEXT (decl, current_class_type);
 431
 432       if (! DECL_USE_TEMPLATE (decl))
 433         {
 434           /* We must check whether the decl refers to template
 435              arguments before push_template_decl_real adds a
 436              reference to the containing template class.  */
 437           int warn = (warn_nontemplate_friend
 438                       && ! funcdef_flag && ! is_friend_template
 439                       && current_template_parms
 440                       && uses_template_parms (decl));
 441
 442           if (is_friend_template
 443               || template_class_depth (current_class_type) != 0)
 444             /* We can't call pushdecl for a template class, since in
 445                general, such a declaration depends on template
 446                parameters.  Instead, we call pushdecl when the class
 447                is instantiated.  */
 448             decl = push_template_decl_real (decl, /*is_friend=*/1);
 449           else if (current_function_decl)
 450             /* This must be a local class, so pushdecl will be ok, and
 451                insert an unqualified friend into the local scope
 452                (rather than the containing namespace scope, which the
 453                next choice will do).  */
 454             decl = pushdecl (decl);
 455           else
 456             {
 457               /* We can't use pushdecl, as we might be in a template
 458                  class specialization, and pushdecl will insert an
 459                  unqualified friend decl into the template parameter
 460                  scope, rather than the namespace containing it.  */
 461               tree ns = decl_namespace_context (decl);
 462
 463               push_nested_namespace (ns);
 464               decl = pushdecl_namespace_level (decl);
 465               pop_nested_namespace (ns);
 466             }
 467
 468           if (warn)
 469             {
 470               static int explained;
 471               warning ("friend declaration `%#D' declares a non-template function", decl);
 472               if (! explained)
 473                 {
 474                   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");
 475                   explained = 1;
 476                 }
 477             }
 478         }
 479
 480       if (decl == error_mark_node)
 481         return error_mark_node;
 482
 483       add_friend (current_class_type,
 484                   is_friend_template ? DECL_TI_TEMPLATE (decl) : decl,
 485                   /*complain=*/true);
 486       DECL_FRIEND_P (decl) = 1;
 487     }
 488
 489   /* Unfortunately, we have to handle attributes here.  Normally we would
 490      handle them in start_decl_1, but since this is a friend decl start_decl_1
 491      never gets to see it.  */
 492
 493   /* Set attributes here so if duplicate decl, will have proper attributes.  */
 494   cplus_decl_attributes (&decl, attrlist, 0);
 495
 496   return decl;
 497 }