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_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     {
 282       /* [temp.friend]
 283
 284            A friend of a class or class template can be a function or
 285            class template, a specialization of a function template or
 286            class template, or an ordinary (nontemplate) function or
 287            class.
 288
 289          But, we're looking at something like:
 290
 291            template <class T> friend typename S<T>::X;
 292
 293          which isn't any of these.  */
 294       cp_error ("typename type `%T' declared `friend'",
 295                 friend_type);
 296       return;
 297     }
 298
 299   GNU_xref_hier (type, friend_type, 0, 0, 1);
 300
 301   if (is_template_friend)
 302     friend_type = CLASSTYPE_TI_TEMPLATE (friend_type);
 303
 304   classes = CLASSTYPE_FRIEND_CLASSES (type);
 305   while (classes
 306          /* Stop if we find the same type on the list.  */
 307          && !(TREE_CODE (TREE_VALUE (classes)) == TEMPLATE_DECL ?
 308               friend_type == TREE_VALUE (classes) :
 309               same_type_p (TREE_VALUE (classes), friend_type)))
 310     classes = TREE_CHAIN (classes);
 311   if (classes)
 312     cp_warning ("`%T' is already a friend of `%T'",
 313                 TREE_VALUE (classes), type);
 314   else
 315     {
 316       CLASSTYPE_FRIEND_CLASSES (type)
 317         = tree_cons (NULL_TREE, friend_type, CLASSTYPE_FRIEND_CLASSES (type));
 318       if (is_template_friend)
 319         friend_type = TREE_TYPE (friend_type);
 320       if (!uses_template_parms (type))
 321         CLASSTYPE_BEFRIENDING_CLASSES (friend_type)
 322           = tree_cons (NULL_TREE, type,
 323                        CLASSTYPE_BEFRIENDING_CLASSES (friend_type));
 324     }
 325 }
 326
 327 /* Main friend processor.  This is large, and for modularity purposes,
 328    has been removed from grokdeclarator.  It returns `void_type_node'
 329    to indicate that something happened, though a FIELD_DECL is
 330    not returned.
 331
 332    CTYPE is the class this friend belongs to.
 333
 334    DECLARATOR is the name of the friend.
 335
 336    DECL is the FUNCTION_DECL that the friend is.
 337
 338    In case we are parsing a friend which is part of an inline
 339    definition, we will need to store PARM_DECL chain that comes
 340    with it into the DECL_ARGUMENTS slot of the FUNCTION_DECL.
 341
 342    FLAGS is just used for `grokclassfn'.
 343
 344    QUALS say what special qualifies should apply to the object
 345    pointed to by `this'.  */
 346
 347 tree
 348 do_friend (ctype, declarator, decl, parmdecls, attrlist,
 349            flags, quals, funcdef_flag)
 350      tree ctype, declarator, decl, parmdecls, attrlist;
 351      enum overload_flags flags;
 352      tree quals;
 353      int funcdef_flag;
 354 {
 355   int is_friend_template = 0;
 356   tree prefix_attributes, attributes;
 357
 358   /* Every decl that gets here is a friend of something.  */
 359   DECL_FRIEND_P (decl) = 1;
 360
 361   if (TREE_CODE (declarator) == TEMPLATE_ID_EXPR)
 362     {
 363       declarator = TREE_OPERAND (declarator, 0);
 364       if (TREE_CODE (declarator) == LOOKUP_EXPR)
 365         declarator = TREE_OPERAND (declarator, 0);
 366       if (is_overloaded_fn (declarator))
 367         declarator = DECL_NAME (get_first_fn (declarator));
 368     }
 369
 370   if (TREE_CODE (decl) != FUNCTION_DECL)
 371     my_friendly_abort (990513);
 372
 373   is_friend_template = PROCESSING_REAL_TEMPLATE_DECL_P ();
 374
 375   if (ctype)
 376     {
 377       tree cname = TYPE_NAME (ctype);
 378       if (TREE_CODE (cname) == TYPE_DECL)
 379         cname = DECL_NAME (cname);
 380
 381       /* A method friend.  */
 382       if (flags == NO_SPECIAL && ctype && declarator == cname)
 383         DECL_CONSTRUCTOR_P (decl) = 1;
 384
 385       /* This will set up DECL_ARGUMENTS for us.  */
 386       grokclassfn (ctype, decl, flags, quals);
 387
 388       if (is_friend_template)
 389         decl = DECL_TI_TEMPLATE (push_template_decl (decl));
 390       else if (template_class_depth (current_class_type))
 391         decl = push_template_decl_real (decl, /*is_friend=*/1);
 392
 393       /* We can't do lookup in a type that involves template
 394          parameters.  Instead, we rely on tsubst_friend_function
 395          to check the validity of the declaration later.  */
 396       if (uses_template_parms (ctype))
 397         add_friend (current_class_type, decl);
 398       /* A nested class may declare a member of an enclosing class
 399          to be a friend, so we do lookup here even if CTYPE is in
 400          the process of being defined.  */
 401       else if (TYPE_SIZE (ctype) != 0 || TYPE_BEING_DEFINED (ctype))
 402         {
 403           decl = check_classfn (ctype, decl);
 404
 405           if (decl)
 406             add_friend (current_class_type, decl);
 407         }
 408       else
 409         cp_error ("member `%D' declared as friend before type `%T' defined",
 410                   decl, ctype);
 411     }
 412   /* A global friend.
 413      @@ or possibly a friend from a base class ?!?  */
 414   else if (TREE_CODE (decl) == FUNCTION_DECL)
 415     {
 416       /* Friends must all go through the overload machinery,
 417          even though they may not technically be overloaded.
 418
 419          Note that because classes all wind up being top-level
 420          in their scope, their friend wind up in top-level scope as well.  */
 421       DECL_ARGUMENTS (decl) = parmdecls;
 422       if (funcdef_flag)
 423         DECL_CLASS_CONTEXT (decl) = current_class_type;
 424
 425       if (! DECL_USE_TEMPLATE (decl))
 426         {
 427           /* We can call pushdecl here, because the TREE_CHAIN of this
 428              FUNCTION_DECL is not needed for other purposes.  Don't do
 429              this for a template instantiation.  However, we don't
 430              call pushdecl() for a friend function of a template
 431              class, since in general, such a declaration depends on
 432              template parameters.  Instead, we call pushdecl when the
 433              class is instantiated.  */
 434           if (!is_friend_template
 435               && template_class_depth (current_class_type) == 0)
 436             decl = pushdecl (decl);
 437           else
 438             decl = push_template_decl_real (decl, /*is_friend=*/1);
 439
 440           if (warn_nontemplate_friend
 441               && ! funcdef_flag && ! flag_guiding_decls && ! is_friend_template
 442               && current_template_parms && uses_template_parms (decl))
 443             {
 444               static int explained;
 445               cp_warning ("friend declaration `%#D'", decl);
 446               warning ("  declares a non-template function");
 447               if (! explained)
 448                 {
 449                   warning ("  (if this is not what you intended, make sure");
 450                   warning ("  the function template has already been declared,");
 451                   warning ("  and add <> after the function name here)");
 452                   warning ("  -Wno-non-template-friend disables this warning.");
 453                   explained = 1;
 454                 }
 455             }
 456         }
 457
 458       make_decl_rtl (decl, NULL_PTR, 1);
 459       add_friend (current_class_type,
 460                   is_friend_template ? DECL_TI_TEMPLATE (decl) : decl);
 461       DECL_FRIEND_P (decl) = 1;
 462     }
 463
 464   /* Unfortunately, we have to handle attributes here.  Normally we would
 465      handle them in start_decl_1, but since this is a friend decl start_decl_1
 466      never gets to see it.  */
 467
 468   if (attrlist)
 469     {
 470       attributes = TREE_PURPOSE (attrlist);
 471       prefix_attributes = TREE_VALUE (attrlist);
 472     }
 473   else
 474     {
 475       attributes = NULL_TREE;
 476       prefix_attributes = NULL_TREE;
 477     }
 478
 479 #ifdef SET_DEFAULT_DECL_ATTRIBUTES
 480   SET_DEFAULT_DECL_ATTRIBUTES (decl, attributes);
 481 #endif
 482
 483   /* Set attributes here so if duplicate decl, will have proper attributes.  */
 484   cplus_decl_attributes (decl, attributes, prefix_attributes);
 485
 486   return decl;
 487 }