gcc/cp/friend.c

   1 /* Help friends in C++.
   2    Copyright (C) 1997, 1998, 1999, 2000 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 /* Friend data structures are described in cp-tree.h.  */
  31
  32 /* Returns non-zero if SUPPLICANT is a friend of TYPE.  */
  33
  34 int
  35 is_friend (type, supplicant)
  36      tree type, supplicant;
  37 {
  38   int declp;
  39   register tree list;
  40   tree context;
  41
  42   if (supplicant == NULL_TREE || type == NULL_TREE)
  43     return 0;
  44
  45   declp = (TREE_CODE_CLASS (TREE_CODE (supplicant)) == 'd');
  46
  47   if (declp)
  48     /* It's a function decl.  */
  49     {
  50       tree list = DECL_FRIENDLIST (TYPE_MAIN_DECL (type));
  51       tree name = DECL_NAME (supplicant);
  52       tree ctype;
  53
  54       if (DECL_FUNCTION_MEMBER_P (supplicant))
  55         ctype = DECL_CLASS_CONTEXT (supplicant);
  56       else
  57         ctype = NULL_TREE;
  58
  59       for (; list ; list = TREE_CHAIN (list))
  60         {
  61           if (name == FRIEND_NAME (list))
  62             {
  63               tree friends = FRIEND_DECLS (list);
  64               for (; friends ; friends = TREE_CHAIN (friends))
  65                 {
  66                   if (same_type_p (ctype, TREE_PURPOSE (friends)))
  67                     return 1;
  68
  69                   if (TREE_VALUE (friends) == NULL_TREE)
  70                     continue;
  71
  72                   if (supplicant == TREE_VALUE (friends))
  73                     return 1;
  74
  75                   /* With -fguiding-decls we are more lenient about
  76                      friendship.  This is bogus in general since two
  77                      specializations of a template with non-type
  78                      template parameters may have the same type, but
  79                      be different.
  80
  81                      Temporarily, we are also more lenient to deal
  82                      with nested friend functions, for which there can
  83                      be more than one FUNCTION_DECL, despite being the
  84                      same function.  When that's fixed, the
  85                      FUNCTION_MEMBER_P bit can go.  */
  86                   if ((flag_guiding_decls
  87                        || DECL_FUNCTION_MEMBER_P (supplicant))
  88                       && same_type_p (TREE_TYPE (supplicant),
  89                                       TREE_TYPE (TREE_VALUE (friends))))
  90                     return 1;
  91
  92                   if (TREE_CODE (TREE_VALUE (friends)) == TEMPLATE_DECL
  93                       && is_specialization_of (supplicant,
  94                                                TREE_VALUE (friends)))
  95                     return 1;
  96                 }
  97               break;
  98             }
  99         }
 100     }
 101   else
 102     /* It's a type.  */
 103     {
 104       if (type == supplicant)
 105         return 1;
 106
 107       list = CLASSTYPE_FRIEND_CLASSES (TREE_TYPE (TYPE_MAIN_DECL (type)));
 108       for (; list ; list = TREE_CHAIN (list))
 109         {
 110           tree t = TREE_VALUE (list);
 111
 112           if (TREE_CODE (t) == TEMPLATE_DECL ?
 113               is_specialization_of (TYPE_MAIN_DECL (supplicant), t) :
 114               same_type_p (supplicant, t))
 115             return 1;
 116         }
 117     }
 118
 119   if (declp && DECL_FUNCTION_MEMBER_P (supplicant))
 120     context = DECL_CLASS_CONTEXT (supplicant);
 121   else if (! declp)
 122     /* Local classes have the same access as the enclosing function.  */
 123     context = hack_decl_function_context (TYPE_MAIN_DECL (supplicant));
 124   else
 125     context = NULL_TREE;
 126
 127   /* A namespace is not friend to anybody. */
 128   if (context && TREE_CODE (context) == NAMESPACE_DECL)
 129     context = NULL_TREE;
 130
 131   if (context)
 132     return is_friend (type, context);
 133
 134   return 0;
 135 }
 136
 137 /* Add a new friend to the friends of the aggregate type TYPE.
 138    DECL is the FUNCTION_DECL of the friend being added.  */
 139
 140 void
 141 add_friend (type, decl)
 142      tree type, decl;
 143 {
 144   tree typedecl;
 145   tree list;
 146   tree name;
 147
 148   if (decl == error_mark_node)
 149     return;
 150
 151   typedecl = TYPE_MAIN_DECL (type);
 152   list = DECL_FRIENDLIST (typedecl);
 153   name = DECL_NAME (decl);
 154   type = TREE_TYPE (typedecl);
 155
 156   while (list)
 157     {
 158       if (name == FRIEND_NAME (list))
 159         {
 160           tree friends = FRIEND_DECLS (list);
 161           for (; friends ; friends = TREE_CHAIN (friends))
 162             {
 163               if (decl == TREE_VALUE (friends))
 164                 {
 165                   cp_warning ("`%D' is already a friend of class `%T'",
 166                               decl, type);
 167                   cp_warning_at ("previous friend declaration of `%D'",
 168                                  TREE_VALUE (friends));
 169                   return;
 170                 }
 171             }
 172           TREE_VALUE (list) = tree_cons (error_mark_node, decl,
 173                                          TREE_VALUE (list));
 174           return;
 175         }
 176       list = TREE_CHAIN (list);
 177     }
 178
 179   DECL_FRIENDLIST (typedecl)
 180     = tree_cons (DECL_NAME (decl), build_tree_list (error_mark_node, decl),
 181                  DECL_FRIENDLIST (typedecl));
 182   if (!uses_template_parms (type))
 183     DECL_BEFRIENDING_CLASSES (decl)
 184       = tree_cons (NULL_TREE, type,
 185                    DECL_BEFRIENDING_CLASSES (decl));
 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 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 == FRIEND_NAME (list))
 201         {
 202           tree friends = FRIEND_DECLS (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 }
 228
 229 /* Make FRIEND_TYPE a friend class to TYPE.  If FRIEND_TYPE has already
 230    been defined, we make all of its member functions friends of
 231    TYPE.  If not, we make it a pending friend, which can later be added
 232    when its definition is seen.  If a type is defined, then its TYPE_DECL's
 233    DECL_UNDEFINED_FRIENDS contains a (possibly empty) list of friend
 234    classes that are not defined.  If a type has not yet been defined,
 235    then the DECL_WAITING_FRIENDS contains a list of types
 236    waiting to make it their friend.  Note that these two can both
 237    be in use at the same time!  */
 238
 239 void
 240 make_friend_class (type, friend_type)
 241      tree type, friend_type;
 242 {
 243   tree classes;
 244   int is_template_friend;
 245
 246   if (! IS_AGGR_TYPE (friend_type))
 247     {
 248       cp_error ("invalid type `%T' declared `friend'", friend_type);
 249       return;
 250     }
 251
 252   if (CLASS_TYPE_P (friend_type)
 253       && CLASSTYPE_TEMPLATE_SPECIALIZATION (friend_type)
 254       && uses_template_parms (friend_type))
 255     {
 256       /* [temp.friend]
 257
 258          Friend declarations shall not declare partial
 259          specializations.  */
 260       cp_error ("partial specialization `%T' declared `friend'",
 261                 friend_type);
 262       return;
 263     }
 264
 265   if (processing_template_decl > template_class_depth (type))
 266     /* If the TYPE is a template then it makes sense for it to be
 267        friends with itself; this means that each instantiation is
 268        friends with all other instantiations.  */
 269     is_template_friend = 1;
 270   else if (same_type_p (type, friend_type))
 271     {
 272       pedwarn ("class `%s' is implicitly friends with itself",
 273                TYPE_NAME_STRING (type));
 274       return;
 275     }
 276   else
 277     is_template_friend = 0;
 278
 279   if (is_template_friend
 280       && (TREE_CODE (friend_type) == TYPENAME_TYPE
 281           || TREE_CODE (friend_type) == TEMPLATE_TYPE_PARM))
 282     {
 283       /* [temp.friend]
 284
 285            A friend of a class or class template can be a function or
 286            class template, a specialization of a function template or
 287            class template, or an ordinary (nontemplate) function or
 288            class.
 289
 290          But, we're looking at something like:
 291
 292            template <class T> friend typename S<T>::X;
 293
 294          or:
 295
 296            template <class T> friend class T;
 297
 298          which isn't any of these.  */
 299       if (TREE_CODE (friend_type) == TYPENAME_TYPE)
 300         cp_error ("typename type `%T' declared `friend'",
 301                   friend_type);
 302       else
 303         cp_error ("template parameter type `%T' declared `friend'",
 304                   friend_type);
 305       return;
 306     }
 307
 308   GNU_xref_hier (type, friend_type, 0, 0, 1);
 309
 310   if (is_template_friend)
 311     friend_type = CLASSTYPE_TI_TEMPLATE (friend_type);
 312
 313   classes = CLASSTYPE_FRIEND_CLASSES (type);
 314   while (classes
 315          /* Stop if we find the same type on the list.  */
 316          && !(TREE_CODE (TREE_VALUE (classes)) == TEMPLATE_DECL ?
 317               friend_type == TREE_VALUE (classes) :
 318               same_type_p (TREE_VALUE (classes), friend_type)))
 319     classes = TREE_CHAIN (classes);
 320   if (classes)
 321     cp_warning ("`%T' is already a friend of `%T'",
 322                 TREE_VALUE (classes), type);
 323   else
 324     {
 325       CLASSTYPE_FRIEND_CLASSES (type)
 326         = tree_cons (NULL_TREE, friend_type, CLASSTYPE_FRIEND_CLASSES (type));
 327       if (is_template_friend)
 328         friend_type = TREE_TYPE (friend_type);
 329       if (!uses_template_parms (type))
 330         CLASSTYPE_BEFRIENDING_CLASSES (friend_type)
 331           = tree_cons (NULL_TREE, type,
 332                        CLASSTYPE_BEFRIENDING_CLASSES (friend_type));
 333     }
 334 }
 335
 336 /* Main friend processor.  This is large, and for modularity purposes,
 337    has been removed from grokdeclarator.  It returns `void_type_node'
 338    to indicate that something happened, though a FIELD_DECL is
 339    not returned.
 340
 341    CTYPE is the class this friend belongs to.
 342
 343    DECLARATOR is the name of the friend.
 344
 345    DECL is the FUNCTION_DECL that the friend is.
 346
 347    In case we are parsing a friend which is part of an inline
 348    definition, we will need to store PARM_DECL chain that comes
 349    with it into the DECL_ARGUMENTS slot of the FUNCTION_DECL.
 350
 351    FLAGS is just used for `grokclassfn'.
 352
 353    QUALS say what special qualifies should apply to the object
 354    pointed to by `this'.  */
 355
 356 tree
 357 do_friend (ctype, declarator, decl, parmdecls, attrlist,
 358            flags, quals, funcdef_flag)
 359      tree ctype, declarator, decl, parmdecls, attrlist;
 360      enum overload_flags flags;
 361      tree quals;
 362      int funcdef_flag;
 363 {
 364   int is_friend_template = 0;
 365   tree prefix_attributes, attributes;
 366
 367   /* Every decl that gets here is a friend of something.  */
 368   DECL_FRIEND_P (decl) = 1;
 369
 370   if (TREE_CODE (declarator) == TEMPLATE_ID_EXPR)
 371     {
 372       declarator = TREE_OPERAND (declarator, 0);
 373       if (TREE_CODE (declarator) == LOOKUP_EXPR)
 374         declarator = TREE_OPERAND (declarator, 0);
 375       if (is_overloaded_fn (declarator))
 376         declarator = DECL_NAME (get_first_fn (declarator));
 377     }
 378
 379   if (TREE_CODE (decl) != FUNCTION_DECL)
 380     my_friendly_abort (990513);
 381
 382   is_friend_template = PROCESSING_REAL_TEMPLATE_DECL_P ();
 383
 384   if (ctype)
 385     {
 386       tree cname = TYPE_NAME (ctype);
 387       if (TREE_CODE (cname) == TYPE_DECL)
 388         cname = DECL_NAME (cname);
 389
 390       /* A method friend.  */
 391       if (flags == NO_SPECIAL && ctype && declarator == cname)
 392         DECL_CONSTRUCTOR_P (decl) = 1;
 393
 394       /* This will set up DECL_ARGUMENTS for us.  */
 395       grokclassfn (ctype, decl, flags, quals);
 396
 397       if (is_friend_template)
 398         decl = DECL_TI_TEMPLATE (push_template_decl (decl));
 399       else if (template_class_depth (current_class_type))
 400         decl = push_template_decl_real (decl, /*is_friend=*/1);
 401
 402       /* We can't do lookup in a type that involves template
 403          parameters.  Instead, we rely on tsubst_friend_function
 404          to check the validity of the declaration later.  */
 405       if (processing_template_decl)
 406         add_friend (current_class_type, decl);
 407       /* A nested class may declare a member of an enclosing class
 408          to be a friend, so we do lookup here even if CTYPE is in
 409          the process of being defined.  */
 410       else if (TYPE_SIZE (ctype) != 0 || TYPE_BEING_DEFINED (ctype))
 411         {
 412           decl = check_classfn (ctype, decl);
 413
 414           if (decl)
 415             add_friend (current_class_type, decl);
 416         }
 417       else
 418         cp_error ("member `%D' declared as friend before type `%T' defined",
 419                   decl, ctype);
 420     }
 421   /* A global friend.
 422      @@ or possibly a friend from a base class ?!?  */
 423   else if (TREE_CODE (decl) == FUNCTION_DECL)
 424     {
 425       /* Friends must all go through the overload machinery,
 426          even though they may not technically be overloaded.
 427
 428          Note that because classes all wind up being top-level
 429          in their scope, their friend wind up in top-level scope as well.  */
 430       DECL_ARGUMENTS (decl) = parmdecls;
 431       if (funcdef_flag)
 432         DECL_CLASS_CONTEXT (decl) = current_class_type;
 433
 434       if (! DECL_USE_TEMPLATE (decl))
 435         {
 436           /* We can call pushdecl here, because the TREE_CHAIN of this
 437              FUNCTION_DECL is not needed for other purposes.  Don't do
 438              this for a template instantiation.  However, we don't
 439              call pushdecl() for a friend function of a template
 440              class, since in general, such a declaration depends on
 441              template parameters.  Instead, we call pushdecl when the
 442              class is instantiated.  */
 443           if (!is_friend_template
 444               && template_class_depth (current_class_type) == 0)
 445             decl = pushdecl (decl);
 446           else
 447             decl = push_template_decl_real (decl, /*is_friend=*/1);
 448
 449           if (warn_nontemplate_friend
 450               && ! funcdef_flag && ! flag_guiding_decls && ! is_friend_template
 451               && current_template_parms && uses_template_parms (decl))
 452             {
 453               static int explained;
 454               cp_warning ("friend declaration `%#D'", decl);
 455               warning ("  declares a non-template function");
 456               if (! explained)
 457                 {
 458                   warning ("  (if this is not what you intended, make sure");
 459                   warning ("  the function template has already been declared,");
 460                   warning ("  and add <> after the function name here)");
 461                   warning ("  -Wno-non-template-friend disables this warning.");
 462                   explained = 1;
 463                 }
 464             }
 465         }
 466
 467       make_decl_rtl (decl, NULL_PTR, 1);
 468       add_friend (current_class_type,
 469                   is_friend_template ? DECL_TI_TEMPLATE (decl) : decl);
 470       DECL_FRIEND_P (decl) = 1;
 471     }
 472
 473   /* Unfortunately, we have to handle attributes here.  Normally we would
 474      handle them in start_decl_1, but since this is a friend decl start_decl_1
 475      never gets to see it.  */
 476
 477   if (attrlist)
 478     {
 479       attributes = TREE_PURPOSE (attrlist);
 480       prefix_attributes = TREE_VALUE (attrlist);
 481     }
 482   else
 483     {
 484       attributes = NULL_TREE;
 485       prefix_attributes = NULL_TREE;
 486     }
 487
 488 #ifdef SET_DEFAULT_DECL_ATTRIBUTES
 489   SET_DEFAULT_DECL_ATTRIBUTES (decl, attributes);
 490 #endif
 491
 492   /* Set attributes here so if duplicate decl, will have proper attributes.  */
 493   cplus_decl_attributes (decl, attributes, prefix_attributes);
 494
 495   return decl;
 496 }