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 /* 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_SIGNATURE (type))
 247     {
 248       error ("`friend' declaration in signature definition");
 249       return;
 250     }
 251   if (IS_SIGNATURE (friend_type) || ! IS_AGGR_TYPE (friend_type))
 252     {
 253       cp_error ("invalid type `%T' declared `friend'", friend_type);
 254       return;
 255     }
 256
 257   if (CLASS_TYPE_P (friend_type)
 258       && CLASSTYPE_TEMPLATE_SPECIALIZATION (friend_type)
 259       && uses_template_parms (friend_type))
 260     {
 261       /* [temp.friend]
 262
 263          Friend declarations shall not declare partial
 264          specializations.  */
 265       cp_error ("partial specialization `%T' declared `friend'",
 266                 friend_type);
 267       return;
 268     }
 269
 270   if (processing_template_decl > template_class_depth (type))
 271     /* If the TYPE is a template then it makes sense for it to be
 272        friends with itself; this means that each instantiation is
 273        friends with all other instantiations.  */
 274     is_template_friend = 1;
 275   else if (same_type_p (type, friend_type))
 276     {
 277       pedwarn ("class `%s' is implicitly friends with itself",
 278                TYPE_NAME_STRING (type));
 279       return;
 280     }
 281   else
 282     is_template_friend = 0;
 283
 284   if (is_template_friend
 285       && TREE_CODE (friend_type) == TYPENAME_TYPE)
 286     {
 287       /* [temp.friend]
 288
 289            A friend of a class or class template can be a function or
 290            class template, a specialization of a function template or
 291            class template, or an ordinary (nontemplate) function or
 292            class.
 293
 294          But, we're looking at something like:
 295
 296            template <class T> friend typename S<T>::X;
 297
 298          which isn't any of these.  */
 299       cp_error ("typename type `%T' declare `friend'",
 300                 friend_type);
 301       return;
 302     }
 303
 304   GNU_xref_hier (type, friend_type, 0, 0, 1);
 305
 306   if (is_template_friend)
 307     friend_type = CLASSTYPE_TI_TEMPLATE (friend_type);
 308
 309   classes = CLASSTYPE_FRIEND_CLASSES (type);
 310   while (classes
 311          /* Stop if we find the same type on the list.  */
 312          && !(TREE_CODE (TREE_VALUE (classes)) == TEMPLATE_DECL ?
 313               friend_type == TREE_VALUE (classes) :
 314               same_type_p (TREE_VALUE (classes), friend_type)))
 315     classes = TREE_CHAIN (classes);
 316   if (classes)
 317     cp_warning ("`%T' is already a friend of `%T'",
 318                 TREE_VALUE (classes), type);
 319   else
 320     {
 321       CLASSTYPE_FRIEND_CLASSES (type)
 322         = tree_cons (NULL_TREE, friend_type, CLASSTYPE_FRIEND_CLASSES (type));
 323       if (is_template_friend)
 324         friend_type = TREE_TYPE (friend_type);
 325       if (!uses_template_parms (type))
 326         CLASSTYPE_BEFRIENDING_CLASSES (friend_type)
 327           = tree_cons (NULL_TREE, type,
 328                        CLASSTYPE_BEFRIENDING_CLASSES (friend_type));
 329     }
 330 }
 331
 332 /* Main friend processor.  This is large, and for modularity purposes,
 333    has been removed from grokdeclarator.  It returns `void_type_node'
 334    to indicate that something happened, though a FIELD_DECL is
 335    not returned.
 336
 337    CTYPE is the class this friend belongs to.
 338
 339    DECLARATOR is the name of the friend.
 340
 341    DECL is the FUNCTION_DECL that the friend is.
 342
 343    In case we are parsing a friend which is part of an inline
 344    definition, we will need to store PARM_DECL chain that comes
 345    with it into the DECL_ARGUMENTS slot of the FUNCTION_DECL.
 346
 347    FLAGS is just used for `grokclassfn'.
 348
 349    QUALS say what special qualifies should apply to the object
 350    pointed to by `this'.  */
 351
 352 tree
 353 do_friend (ctype, declarator, decl, parmdecls, attrlist,
 354            flags, quals, funcdef_flag)
 355      tree ctype, declarator, decl, parmdecls, attrlist;
 356      enum overload_flags flags;
 357      tree quals;
 358      int funcdef_flag;
 359 {
 360   int is_friend_template = 0;
 361   tree prefix_attributes, attributes;
 362
 363   /* Every decl that gets here is a friend of something.  */
 364   DECL_FRIEND_P (decl) = 1;
 365
 366   if (TREE_CODE (declarator) == TEMPLATE_ID_EXPR)
 367     {
 368       declarator = TREE_OPERAND (declarator, 0);
 369       if (TREE_CODE (declarator) == LOOKUP_EXPR)
 370         declarator = TREE_OPERAND (declarator, 0);
 371       if (is_overloaded_fn (declarator))
 372         declarator = DECL_NAME (get_first_fn (declarator));
 373     }
 374
 375   if (TREE_CODE (decl) != FUNCTION_DECL)
 376     my_friendly_abort (990513);
 377
 378   is_friend_template = PROCESSING_REAL_TEMPLATE_DECL_P ();
 379
 380   if (ctype)
 381     {
 382       tree cname = TYPE_NAME (ctype);
 383       if (TREE_CODE (cname) == TYPE_DECL)
 384         cname = DECL_NAME (cname);
 385
 386       /* A method friend.  */
 387       if (flags == NO_SPECIAL && ctype && declarator == cname)
 388         DECL_CONSTRUCTOR_P (decl) = 1;
 389
 390       /* This will set up DECL_ARGUMENTS for us.  */
 391       grokclassfn (ctype, decl, flags, quals);
 392
 393       if (is_friend_template)
 394         decl = DECL_TI_TEMPLATE (push_template_decl (decl));
 395       else if (template_class_depth (current_class_type))
 396         decl = push_template_decl_real (decl, /*is_friend=*/1);
 397
 398       /* We can't do lookup in a type that involves template
 399          parameters.  Instead, we rely on tsubst_friend_function
 400          to check the validity of the declaration later.  */
 401       if (uses_template_parms (ctype))
 402         add_friend (current_class_type, decl);
 403       /* A nested class may declare a member of an enclosing class
 404          to be a friend, so we do lookup here even if CTYPE is in
 405          the process of being defined.  */
 406       else if (TYPE_SIZE (ctype) != 0 || TYPE_BEING_DEFINED (ctype))
 407         {
 408           decl = check_classfn (ctype, decl);
 409
 410           if (decl)
 411             add_friend (current_class_type, decl);
 412         }
 413       else
 414         cp_error ("member `%D' declared as friend before type `%T' defined",
 415                   decl, ctype);
 416     }
 417   /* A global friend.
 418      @@ or possibly a friend from a base class ?!?  */
 419   else if (TREE_CODE (decl) == FUNCTION_DECL)
 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       DECL_ARGUMENTS (decl) = parmdecls;
 427       if (funcdef_flag)
 428         DECL_CLASS_CONTEXT (decl) = current_class_type;
 429
 430       if (! DECL_USE_TEMPLATE (decl))
 431         {
 432           /* We can call pushdecl here, because the TREE_CHAIN of this
 433              FUNCTION_DECL is not needed for other purposes.  Don't do
 434              this for a template instantiation.  However, we don't
 435              call pushdecl() for a friend function of a template
 436              class, since in general, such a declaration depends on
 437              template parameters.  Instead, we call pushdecl when the
 438              class is instantiated.  */
 439           if (!is_friend_template
 440               && template_class_depth (current_class_type) == 0)
 441             decl = pushdecl (decl);
 442           else
 443             decl = push_template_decl_real (decl, /*is_friend=*/1);
 444
 445           if (warn_nontemplate_friend
 446               && ! funcdef_flag && ! flag_guiding_decls && ! is_friend_template
 447               && current_template_parms && uses_template_parms (decl))
 448             {
 449               static int explained;
 450               cp_warning ("friend declaration `%#D'", decl);
 451               warning ("  declares a non-template function");
 452               if (! explained)
 453                 {
 454                   warning ("  (if this is not what you intended, make sure");
 455                   warning ("  the function template has already been declared,");
 456                   warning ("  and add <> after the function name here)");
 457                   warning ("  -Wno-non-template-friend disables this warning.");
 458                   explained = 1;
 459                 }
 460             }
 461         }
 462
 463       make_decl_rtl (decl, NULL_PTR, 1);
 464       add_friend (current_class_type,
 465                   is_friend_template ? DECL_TI_TEMPLATE (decl) : decl);
 466       DECL_FRIEND_P (decl) = 1;
 467     }
 468
 469   /* Unfortunately, we have to handle attributes here.  Normally we would
 470      handle them in start_decl_1, but since this is a friend decl start_decl_1
 471      never gets to see it.  */
 472
 473   if (attrlist)
 474     {
 475       attributes = TREE_PURPOSE (attrlist);
 476       prefix_attributes = TREE_VALUE (attrlist);
 477     }
 478   else
 479     {
 480       attributes = NULL_TREE;
 481       prefix_attributes = NULL_TREE;
 482     }
 483
 484 #ifdef SET_DEFAULT_DECL_ATTRIBUTES
 485   SET_DEFAULT_DECL_ATTRIBUTES (decl, attributes);
 486 #endif
 487
 488   /* Set attributes here so if duplicate decl, will have proper attributes.  */
 489   cplus_decl_attributes (decl, attributes, prefix_attributes);
 490
 491   return decl;
 492 }