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
 133   if (decl == error_mark_node)
 134     return;
 135
 136   typedecl = TYPE_MAIN_DECL (type);
 137   list = DECL_FRIENDLIST (typedecl);
 138   name = DECL_NAME (decl);
 139   type = TREE_TYPE (typedecl);
 140
 141   while (list)
 142     {
 143       if (name == FRIEND_NAME (list))
 144         {
 145           tree friends = FRIEND_DECLS (list);
 146           for (; friends ; friends = TREE_CHAIN (friends))
 147             {
 148               if (decl == TREE_VALUE (friends))
 149                 {
 150                   if (complain)
 151                     warning ("`%D' is already a friend of class `%T'",
 152                              decl, type);
 153                   return;
 154                 }
 155             }
 156
 157           maybe_add_class_template_decl_list (type, decl, /*friend_p=*/1);
 158
 159           TREE_VALUE (list) = tree_cons (NULL_TREE, decl,
 160                                          TREE_VALUE (list));
 161           return;
 162         }
 163       list = TREE_CHAIN (list);
 164     }
 165
 166   if (DECL_CLASS_SCOPE_P (decl))
 167     perform_or_defer_access_check (TYPE_BINFO (DECL_CONTEXT (decl)), decl);
 168
 169   maybe_add_class_template_decl_list (type, decl, /*friend_p=*/1);
 170
 171   DECL_FRIENDLIST (typedecl)
 172     = tree_cons (DECL_NAME (decl), build_tree_list (NULL_TREE, decl),
 173                  DECL_FRIENDLIST (typedecl));
 174   if (!uses_template_parms (type))
 175     DECL_BEFRIENDING_CLASSES (decl)
 176       = tree_cons (NULL_TREE, type,
 177                    DECL_BEFRIENDING_CLASSES (decl));
 178 }
 179
 180 /* Make FRIEND_TYPE a friend class to TYPE.  If FRIEND_TYPE has already
 181    been defined, we make all of its member functions friends of
 182    TYPE.  If not, we make it a pending friend, which can later be added
 183    when its definition is seen.  If a type is defined, then its TYPE_DECL's
 184    DECL_UNDEFINED_FRIENDS contains a (possibly empty) list of friend
 185    classes that are not defined.  If a type has not yet been defined,
 186    then the DECL_WAITING_FRIENDS contains a list of types
 187    waiting to make it their friend.  Note that these two can both
 188    be in use at the same time!
 189
 190    If COMPLAIN is true, warning about duplicate friend is issued.
 191    We want to have this diagnostics during parsing but not
 192    when a template is being instantiated.  */
 193
 194 void
 195 make_friend_class (tree type, tree friend_type, bool complain)
 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       if (complain)
 228         pedwarn ("class `%T' is implicitly friends with itself",
 229                  type);
 230       return;
 231     }
 232   else
 233     is_template_friend = 0;
 234
 235   /* [temp.friend]
 236
 237      A friend of a class or class template can be a function or
 238      class template, a specialization of a function template or
 239      class template, or an ordinary (nontemplate) function or
 240      class.  */
 241   if (!is_template_friend)
 242     ;/* ok */
 243   else if (TREE_CODE (friend_type) == TYPENAME_TYPE)
 244     {
 245       /* template <class T> friend typename S<T>::X; */
 246       error ("typename type `%#T' declared `friend'", friend_type);
 247       return;
 248     }
 249   else if (TREE_CODE (friend_type) == TEMPLATE_TYPE_PARM)
 250     {
 251       /* template <class T> friend class T; */
 252       error ("template parameter type `%T' declared `friend'", friend_type);
 253       return;
 254     }
 255   else if (!CLASSTYPE_TEMPLATE_INFO (friend_type))
 256     {
 257       /* template <class T> friend class A; where A is not a template */
 258       error ("`%#T' is not a template", friend_type);
 259       return;
 260     }
 261
 262   if (is_template_friend)
 263     friend_type = CLASSTYPE_TI_TEMPLATE (friend_type);
 264
 265   /* See if it is already a friend.  */
 266   for (classes = CLASSTYPE_FRIEND_CLASSES (type);
 267        classes;
 268        classes = TREE_CHAIN (classes))
 269     {
 270       tree probe = TREE_VALUE (classes);
 271
 272       if (TREE_CODE (friend_type) == TEMPLATE_DECL)
 273         {
 274           if (friend_type == probe)
 275             {
 276               if (complain)
 277                 warning ("`%D' is already a friend of `%T'",
 278                          probe, type);
 279               break;
 280             }
 281         }
 282       else if (TREE_CODE (probe) != TEMPLATE_DECL)
 283         {
 284           if (same_type_p (probe, friend_type))
 285             {
 286               if (complain)
 287                 warning ("`%T' is already a friend of `%T'",
 288                          probe, type);
 289               break;
 290             }
 291         }
 292     }
 293
 294   if (!classes)
 295     {
 296       maybe_add_class_template_decl_list (type, friend_type, /*friend_p=*/1);
 297
 298       CLASSTYPE_FRIEND_CLASSES (type)
 299         = tree_cons (NULL_TREE, friend_type, CLASSTYPE_FRIEND_CLASSES (type));
 300       if (is_template_friend)
 301         friend_type = TREE_TYPE (friend_type);
 302       if (!uses_template_parms (type))
 303         CLASSTYPE_BEFRIENDING_CLASSES (friend_type)
 304           = tree_cons (NULL_TREE, type,
 305                        CLASSTYPE_BEFRIENDING_CLASSES (friend_type));
 306     }
 307 }
 308
 309 /* Main friend processor.
 310
 311    CTYPE is the class this friend belongs to.
 312
 313    DECLARATOR is the name of the friend.
 314
 315    DECL is the FUNCTION_DECL that the friend is.
 316
 317    FLAGS is just used for `grokclassfn'.
 318
 319    QUALS say what special qualifies should apply to the object
 320    pointed to by `this'.  */
 321
 322 tree
 323 do_friend (tree ctype, tree declarator, tree decl,
 324            tree attrlist, enum overload_flags flags, tree quals,
 325            int funcdef_flag)
 326 {
 327   /* Every decl that gets here is a friend of something.  */
 328   DECL_FRIEND_P (decl) = 1;
 329
 330   if (TREE_CODE (declarator) == TEMPLATE_ID_EXPR)
 331     {
 332       declarator = TREE_OPERAND (declarator, 0);
 333       if (is_overloaded_fn (declarator))
 334         declarator = DECL_NAME (get_first_fn (declarator));
 335     }
 336
 337   if (TREE_CODE (decl) != FUNCTION_DECL)
 338     abort ();
 339
 340   if (ctype)
 341     {
 342       /* CLASS_TEMPLATE_DEPTH counts the number of template headers for
 343          the enclosing class.  FRIEND_DEPTH counts the number of template
 344          headers used for this friend declaration.  TEMPLATE_MEMBER_P is
 345          true if a template header in FRIEND_DEPTH is intended for
 346          DECLARATOR.  For example, the code
 347
 348            template <class T> struct A {
 349              template <class U> struct B {
 350                template <class V> template <class W>
 351                  friend void C<V>::f(W);
 352              };
 353            };
 354
 355          will eventually give the following results
 356
 357          1. CLASS_TEMPLATE_DEPTH equals 2 (for `T' and `U').
 358          2. FRIEND_DEPTH equals 2 (for `V' and `W').
 359          3. TEMPLATE_MEMBER_P is true (for `W').  */
 360
 361       int class_template_depth = template_class_depth (current_class_type);
 362       int friend_depth = processing_template_decl - class_template_depth;
 363       /* We will figure this out later.  */
 364       bool template_member_p = false;
 365
 366       tree cname = TYPE_NAME (ctype);
 367       if (TREE_CODE (cname) == TYPE_DECL)
 368         cname = DECL_NAME (cname);
 369
 370       /* A method friend.  */
 371       if (flags == NO_SPECIAL && declarator == cname)
 372         DECL_CONSTRUCTOR_P (decl) = 1;
 373
 374       /* This will set up DECL_ARGUMENTS for us.  */
 375       grokclassfn (ctype, decl, flags, quals);
 376
 377       if (friend_depth)
 378         {
 379           if (!uses_template_parms_level (ctype, class_template_depth
 380                                                  + friend_depth))
 381             template_member_p = true;
 382         }
 383
 384       /* A nested class may declare a member of an enclosing class
 385          to be a friend, so we do lookup here even if CTYPE is in
 386          the process of being defined.  */
 387       if (class_template_depth
 388           || COMPLETE_TYPE_P (ctype)
 389           || TYPE_BEING_DEFINED (ctype))
 390         {
 391           if (DECL_TEMPLATE_INFO (decl))
 392             /* DECL is a template specialization.  No need to
 393                build a new TEMPLATE_DECL.  */
 394             ;
 395           else if (class_template_depth)
 396             /* We rely on tsubst_friend_function to check the
 397                validity of the declaration later.  */
 398             decl = push_template_decl_real (decl, /*is_friend=*/1);
 399           else
 400             decl = check_classfn (ctype, decl,
 401                                   template_member_p
 402                                   ? current_template_parms
 403                                   : NULL_TREE);
 404
 405           if (template_member_p && decl && TREE_CODE (decl) == FUNCTION_DECL)
 406             decl = DECL_TI_TEMPLATE (decl);
 407
 408           if (decl)
 409             add_friend (current_class_type, decl, /*complain=*/true);
 410         }
 411       else
 412         error ("member `%D' declared as friend before type `%T' defined",
 413                   decl, ctype);
 414     }
 415   /* A global friend.
 416      @@ or possibly a friend from a base class ?!?  */
 417   else if (TREE_CODE (decl) == FUNCTION_DECL)
 418     {
 419       int is_friend_template = PROCESSING_REAL_TEMPLATE_DECL_P ();
 420
 421       /* Friends must all go through the overload machinery,
 422          even though they may not technically be overloaded.
 423
 424          Note that because classes all wind up being top-level
 425          in their scope, their friend wind up in top-level scope as well.  */
 426       if (funcdef_flag)
 427         SET_DECL_FRIEND_CONTEXT (decl, current_class_type);
 428
 429       if (! DECL_USE_TEMPLATE (decl))
 430         {
 431           /* We must check whether the decl refers to template
 432              arguments before push_template_decl_real adds a
 433              reference to the containing template class.  */
 434           int warn = (warn_nontemplate_friend
 435                       && ! funcdef_flag && ! is_friend_template
 436                       && current_template_parms
 437                       && uses_template_parms (decl));
 438
 439           if (is_friend_template
 440               || template_class_depth (current_class_type) != 0)
 441             /* We can't call pushdecl for a template class, since in
 442                general, such a declaration depends on template
 443                parameters.  Instead, we call pushdecl when the class
 444                is instantiated.  */
 445             decl = push_template_decl_real (decl, /*is_friend=*/1);
 446           else if (current_function_decl)
 447             /* This must be a local class, so pushdecl will be ok, and
 448                insert an unqualified friend into the local scope
 449                (rather than the containing namespace scope, which the
 450                next choice will do).  */
 451             decl = pushdecl (decl);
 452           else
 453             {
 454               /* We can't use pushdecl, as we might be in a template
 455                  class specialization, and pushdecl will insert an
 456                  unqualified friend decl into the template parameter
 457                  scope, rather than the namespace containing it.  */
 458               tree ns = decl_namespace_context (decl);
 459
 460               push_nested_namespace (ns);
 461               decl = pushdecl_namespace_level (decl);
 462               pop_nested_namespace (ns);
 463             }
 464
 465           if (warn)
 466             {
 467               static int explained;
 468               warning ("friend declaration `%#D' declares a non-template function", decl);
 469               if (! explained)
 470                 {
 471                   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");
 472                   explained = 1;
 473                 }
 474             }
 475         }
 476
 477       if (decl == error_mark_node)
 478         return error_mark_node;
 479
 480       add_friend (current_class_type,
 481                   is_friend_template ? DECL_TI_TEMPLATE (decl) : decl,
 482                   /*complain=*/true);
 483       DECL_FRIEND_P (decl) = 1;
 484     }
 485
 486   /* Unfortunately, we have to handle attributes here.  Normally we would
 487      handle them in start_decl_1, but since this is a friend decl start_decl_1
 488      never gets to see it.  */
 489
 490   /* Set attributes here so if duplicate decl, will have proper attributes.  */
 491   cplus_decl_attributes (&decl, attrlist, 0);
 492
 493   return decl;
 494 }