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   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    In case we are parsing a friend which is part of an inline
 318    definition, we will need to store PARM_DECL chain that comes
 319    with it into the DECL_ARGUMENTS slot of the FUNCTION_DECL.
 320
 321    FLAGS is just used for `grokclassfn'.
 322
 323    QUALS say what special qualifies should apply to the object
 324    pointed to by `this'.  */
 325
 326 tree
 327 do_friend (tree ctype, tree declarator, tree decl, tree parmdecls,
 328            tree attrlist, enum overload_flags flags, tree quals,
 329            int funcdef_flag)
 330 {
 331   /* Every decl that gets here is a friend of something.  */
 332   DECL_FRIEND_P (decl) = 1;
 333
 334   if (TREE_CODE (declarator) == TEMPLATE_ID_EXPR)
 335     {
 336       declarator = TREE_OPERAND (declarator, 0);
 337       if (is_overloaded_fn (declarator))
 338         declarator = DECL_NAME (get_first_fn (declarator));
 339     }
 340
 341   if (TREE_CODE (decl) != FUNCTION_DECL)
 342     abort ();
 343
 344   if (ctype)
 345     {
 346       /* CLASS_TEMPLATE_DEPTH counts the number of template headers for
 347          the enclosing class.  FRIEND_DEPTH counts the number of template
 348          headers used for this friend declaration.  TEMPLATE_MEMBER_P is
 349          true if a template header in FRIEND_DEPTH is intended for
 350          DECLARATOR.  For example, the code
 351
 352            template <class T> struct A {
 353              template <class U> struct B {
 354                template <class V> template <class W>
 355                  friend void C<V>::f(W);
 356              };
 357            };
 358
 359          will eventually give the following results
 360
 361          1. CLASS_TEMPLATE_DEPTH equals 2 (for `T' and `U').
 362          2. FRIEND_DEPTH equals 2 (for `V' and `W').
 363          3. TEMPLATE_MEMBER_P is true (for `W').  */
 364
 365       int class_template_depth = template_class_depth (current_class_type);
 366       int friend_depth = processing_template_decl - class_template_depth;
 367       /* We will figure this out later.  */
 368       bool template_member_p = false;
 369
 370       tree cname = TYPE_NAME (ctype);
 371       if (TREE_CODE (cname) == TYPE_DECL)
 372         cname = DECL_NAME (cname);
 373
 374       /* A method friend.  */
 375       if (flags == NO_SPECIAL && declarator == cname)
 376         DECL_CONSTRUCTOR_P (decl) = 1;
 377
 378       /* This will set up DECL_ARGUMENTS for us.  */
 379       grokclassfn (ctype, decl, flags, quals);
 380
 381       if (friend_depth)
 382         {
 383           if (!uses_template_parms_level (ctype, class_template_depth
 384                                                  + friend_depth))
 385             template_member_p = true;
 386         }
 387
 388       /* A nested class may declare a member of an enclosing class
 389          to be a friend, so we do lookup here even if CTYPE is in
 390          the process of being defined.  */
 391       if (class_template_depth
 392           || COMPLETE_TYPE_P (ctype)
 393           || TYPE_BEING_DEFINED (ctype))
 394         {
 395           if (DECL_TEMPLATE_INFO (decl))
 396             /* DECL is a template specialization.  No need to
 397                build a new TEMPLATE_DECL.  */
 398             ;
 399           else if (class_template_depth)
 400             /* We rely on tsubst_friend_function to check the
 401                validity of the declaration later.  */
 402             decl = push_template_decl_real (decl, /*is_friend=*/1);
 403           else
 404             decl = check_classfn (ctype, decl, template_member_p);
 405
 406           if (template_member_p && decl && TREE_CODE (decl) == FUNCTION_DECL)
 407             decl = DECL_TI_TEMPLATE (decl);
 408
 409           if (decl)
 410             add_friend (current_class_type, decl, /*complain=*/true);
 411         }
 412       else
 413         error ("member `%D' declared as friend before type `%T' defined",
 414                   decl, ctype);
 415     }
 416   /* A global friend.
 417      @@ or possibly a friend from a base class ?!?  */
 418   else if (TREE_CODE (decl) == FUNCTION_DECL)
 419     {
 420       int is_friend_template = PROCESSING_REAL_TEMPLATE_DECL_P ();
 421
 422       /* Friends must all go through the overload machinery,
 423          even though they may not technically be overloaded.
 424
 425          Note that because classes all wind up being top-level
 426          in their scope, their friend wind up in top-level scope as well.  */
 427       DECL_ARGUMENTS (decl) = parmdecls;
 428       if (funcdef_flag)
 429         SET_DECL_FRIEND_CONTEXT (decl, current_class_type);
 430
 431       if (! DECL_USE_TEMPLATE (decl))
 432         {
 433           /* We must check whether the decl refers to template
 434              arguments before push_template_decl_real adds a
 435              reference to the containing template class.  */
 436           int warn = (warn_nontemplate_friend
 437                       && ! funcdef_flag && ! is_friend_template
 438                       && current_template_parms
 439                       && uses_template_parms (decl));
 440
 441           if (is_friend_template
 442               || template_class_depth (current_class_type) != 0)
 443             /* We can't call pushdecl for a template class, since in
 444                general, such a declaration depends on template
 445                parameters.  Instead, we call pushdecl when the class
 446                is instantiated.  */
 447             decl = push_template_decl_real (decl, /*is_friend=*/1);
 448           else if (current_function_decl)
 449             /* This must be a local class, so pushdecl will be ok, and
 450                insert an unqualified friend into the local scope
 451                (rather than the containing namespace scope, which the
 452                next choice will do).  */
 453             decl = pushdecl (decl);
 454           else
 455             {
 456               /* We can't use pushdecl, as we might be in a template
 457                  class specialization, and pushdecl will insert an
 458                  unqualified friend decl into the template parameter
 459                  scope, rather than the namespace containing it.  */
 460               tree ns = decl_namespace_context (decl);
 461
 462               push_nested_namespace (ns);
 463               decl = pushdecl_namespace_level (decl);
 464               pop_nested_namespace (ns);
 465             }
 466
 467           if (warn)
 468             {
 469               static int explained;
 470               warning ("friend declaration `%#D' declares a non-template function", decl);
 471               if (! explained)
 472                 {
 473                   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");
 474                   explained = 1;
 475                 }
 476             }
 477         }
 478
 479       if (decl == error_mark_node)
 480         return error_mark_node;
 481
 482       add_friend (current_class_type,
 483                   is_friend_template ? DECL_TI_TEMPLATE (decl) : decl,
 484                   /*complain=*/true);
 485       DECL_FRIEND_P (decl) = 1;
 486     }
 487
 488   /* Unfortunately, we have to handle attributes here.  Normally we would
 489      handle them in start_decl_1, but since this is a friend decl start_decl_1
 490      never gets to see it.  */
 491
 492   /* Set attributes here so if duplicate decl, will have proper attributes.  */
 493   cplus_decl_attributes (&decl, attrlist, 0);
 494
 495   return decl;
 496 }