gcc/cp/friend.c

   1 /* Help friends in C++.
   2    Copyright (C) 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005,
   3    2007  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 3, 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 COPYING3.  If not see
  19 <http://www.gnu.org/licenses/>.  */
  20
  21 #include "config.h"
  22 #include "system.h"
  23 #include "coretypes.h"
  24 #include "tm.h"
  25 #include "tree.h"
  26 #include "rtl.h"
  27 #include "expr.h"
  28 #include "cp-tree.h"
  29 #include "flags.h"
  30 #include "output.h"
  31 #include "toplev.h"
  32
  33 /* Friend data structures are described in cp-tree.h.  */
  34
  35 /* Returns nonzero if SUPPLICANT is a friend of TYPE.  */
  36
  37 int
  38 is_friend (tree type, tree supplicant)
  39 {
  40   int declp;
  41   tree list;
  42   tree context;
  43
  44   if (supplicant == NULL_TREE || type == NULL_TREE)
  45     return 0;
  46
  47   declp = DECL_P (supplicant);
  48
  49   if (declp)
  50     /* It's a function decl.  */
  51     {
  52       tree list = DECL_FRIENDLIST (TYPE_MAIN_DECL (type));
  53       tree name = DECL_NAME (supplicant);
  54
  55       for (; list ; list = TREE_CHAIN (list))
  56         {
  57           if (name == FRIEND_NAME (list))
  58             {
  59               tree friends = FRIEND_DECLS (list);
  60               for (; friends ; friends = TREE_CHAIN (friends))
  61                 {
  62                   tree friend = TREE_VALUE (friends);
  63
  64                   if (friend == NULL_TREE)
  65                     continue;
  66
  67                   if (supplicant == friend)
  68                     return 1;
  69
  70                   if (is_specialization_of_friend (supplicant, friend))
  71                     return 1;
  72                 }
  73               break;
  74             }
  75         }
  76     }
  77   else
  78     /* It's a type.  */
  79     {
  80       if (same_type_p (supplicant, type))
  81         return 1;
  82
  83       list = CLASSTYPE_FRIEND_CLASSES (TREE_TYPE (TYPE_MAIN_DECL (type)));
  84       for (; list ; list = TREE_CHAIN (list))
  85         {
  86           tree t = TREE_VALUE (list);
  87
  88           if (TREE_CODE (t) == TEMPLATE_DECL ?
  89               is_specialization_of_friend (TYPE_MAIN_DECL (supplicant), t) :
  90               same_type_p (supplicant, t))
  91             return 1;
  92         }
  93     }
  94
  95   if (declp)
  96     {
  97       if (DECL_FUNCTION_MEMBER_P (supplicant))
  98         context = DECL_CONTEXT (supplicant);
  99       else
 100         context = NULL_TREE;
 101     }
 102   else
 103     {
 104       if (TYPE_CLASS_SCOPE_P (supplicant))
 105         /* Nested classes get the same access as their enclosing types, as
 106            per DR 45 (this is a change from the standard).  */
 107         context = TYPE_CONTEXT (supplicant);
 108       else
 109         /* Local classes have the same access as the enclosing function.  */
 110         context = decl_function_context (TYPE_MAIN_DECL (supplicant));
 111     }
 112
 113   /* A namespace is not friend to anybody.  */
 114   if (context && TREE_CODE (context) == NAMESPACE_DECL)
 115     context = NULL_TREE;
 116
 117   if (context)
 118     return is_friend (type, context);
 119
 120   return 0;
 121 }
 122
 123 /* Add a new friend to the friends of the aggregate type TYPE.
 124    DECL is the FUNCTION_DECL of the friend being added.
 125
 126    If COMPLAIN is true, warning about duplicate friend is issued.
 127    We want to have this diagnostics during parsing but not
 128    when a template is being instantiated.  */
 129
 130 void
 131 add_friend (tree type, tree decl, bool complain)
 132 {
 133   tree typedecl;
 134   tree list;
 135   tree name;
 136   tree ctx;
 137
 138   if (decl == error_mark_node)
 139     return;
 140
 141   typedecl = TYPE_MAIN_DECL (type);
 142   list = DECL_FRIENDLIST (typedecl);
 143   name = DECL_NAME (decl);
 144   type = TREE_TYPE (typedecl);
 145
 146   while (list)
 147     {
 148       if (name == FRIEND_NAME (list))
 149         {
 150           tree friends = FRIEND_DECLS (list);
 151           for (; friends ; friends = TREE_CHAIN (friends))
 152             {
 153               if (decl == TREE_VALUE (friends))
 154                 {
 155                   if (complain)
 156                     warning (0, "%qD is already a friend of class %qT",
 157                              decl, type);
 158                   return;
 159                 }
 160             }
 161
 162           maybe_add_class_template_decl_list (type, decl, /*friend_p=*/1);
 163
 164           TREE_VALUE (list) = tree_cons (NULL_TREE, decl,
 165                                          TREE_VALUE (list));
 166           return;
 167         }
 168       list = TREE_CHAIN (list);
 169     }
 170
 171   ctx = DECL_CONTEXT (decl);
 172   if (ctx && CLASS_TYPE_P (ctx) && !uses_template_parms (ctx))
 173     perform_or_defer_access_check (TYPE_BINFO (ctx), decl, decl);
 174
 175   maybe_add_class_template_decl_list (type, decl, /*friend_p=*/1);
 176
 177   DECL_FRIENDLIST (typedecl)
 178     = tree_cons (DECL_NAME (decl), build_tree_list (NULL_TREE, decl),
 179                  DECL_FRIENDLIST (typedecl));
 180   if (!uses_template_parms (type))
 181     DECL_BEFRIENDING_CLASSES (decl)
 182       = tree_cons (NULL_TREE, type,
 183                    DECL_BEFRIENDING_CLASSES (decl));
 184 }
 185
 186 /* Make FRIEND_TYPE a friend class to TYPE.  If FRIEND_TYPE has already
 187    been defined, we make all of its member functions friends of
 188    TYPE.  If not, we make it a pending friend, which can later be added
 189    when its definition is seen.  If a type is defined, then its TYPE_DECL's
 190    DECL_UNDEFINED_FRIENDS contains a (possibly empty) list of friend
 191    classes that are not defined.  If a type has not yet been defined,
 192    then the DECL_WAITING_FRIENDS contains a list of types
 193    waiting to make it their friend.  Note that these two can both
 194    be in use at the same time!
 195
 196    If COMPLAIN is true, warning about duplicate friend is issued.
 197    We want to have this diagnostics during parsing but not
 198    when a template is being instantiated.  */
 199
 200 void
 201 make_friend_class (tree type, tree friend_type, bool complain)
 202 {
 203   tree classes;
 204
 205   /* CLASS_TEMPLATE_DEPTH counts the number of template headers for
 206      the enclosing class.  FRIEND_DEPTH counts the number of template
 207      headers used for this friend declaration.  TEMPLATE_MEMBER_P,
 208      defined inside the `if' block for TYPENAME_TYPE case, is true if
 209      a template header in FRIEND_DEPTH is intended for DECLARATOR.
 210      For example, the code
 211
 212        template <class T> struct A {
 213          template <class U> struct B {
 214            template <class V> template <class W>
 215              friend class C<V>::D;
 216          };
 217        };
 218
 219      will eventually give the following results
 220
 221      1. CLASS_TEMPLATE_DEPTH equals 2 (for `T' and `U').
 222      2. FRIEND_DEPTH equals 2 (for `V' and `W').
 223      3. TEMPLATE_MEMBER_P is true (for `W').
 224
 225      The friend is a template friend iff FRIEND_DEPTH is nonzero.  */
 226
 227   int class_template_depth = template_class_depth (type);
 228   int friend_depth = processing_template_decl - class_template_depth;
 229
 230   if (! IS_AGGR_TYPE (friend_type))
 231     {
 232       error ("invalid type %qT declared %<friend%>", friend_type);
 233       return;
 234     }
 235
 236   if (friend_depth)
 237     /* If the TYPE is a template then it makes sense for it to be
 238        friends with itself; this means that each instantiation is
 239        friends with all other instantiations.  */
 240     {
 241       if (CLASS_TYPE_P (friend_type)
 242           && CLASSTYPE_TEMPLATE_SPECIALIZATION (friend_type)
 243           && uses_template_parms (friend_type))
 244         {
 245           /* [temp.friend]
 246              Friend declarations shall not declare partial
 247              specializations.  */
 248           error ("partial specialization %qT declared %<friend%>",
 249                  friend_type);
 250           return;
 251         }
 252     }
 253   else if (same_type_p (type, friend_type))
 254     {
 255       if (complain)
 256         pedwarn ("class %qT is implicitly friends with itself",
 257                  type);
 258       return;
 259     }
 260
 261   /* [temp.friend]
 262
 263      A friend of a class or class template can be a function or
 264      class template, a specialization of a function template or
 265      class template, or an ordinary (nontemplate) function or
 266      class.  */
 267   if (!friend_depth)
 268     ;/* ok */
 269   else if (TREE_CODE (friend_type) == TYPENAME_TYPE)
 270     {
 271       if (TREE_CODE (TYPENAME_TYPE_FULLNAME (friend_type))
 272           == TEMPLATE_ID_EXPR)
 273         {
 274           /* template <class U> friend class T::X<U>; */
 275           /* [temp.friend]
 276              Friend declarations shall not declare partial
 277              specializations.  */
 278           error ("partial specialization %qT declared %<friend%>",
 279                  friend_type);
 280           return;
 281         }
 282       else
 283         {
 284           /* We will figure this out later.  */
 285           bool template_member_p = false;
 286
 287           tree ctype = TYPE_CONTEXT (friend_type);
 288           tree name = TYPE_IDENTIFIER (friend_type);
 289           tree decl;
 290
 291           if (!uses_template_parms_level (ctype, class_template_depth
 292                                                  + friend_depth))
 293             template_member_p = true;
 294
 295           if (class_template_depth)
 296             {
 297               /* We rely on tsubst_friend_class to check the
 298                  validity of the declaration later.  */
 299               if (template_member_p)
 300                 friend_type
 301                   = make_unbound_class_template (ctype,
 302                                                  name,
 303                                                  current_template_parms,
 304                                                  tf_error);
 305               else
 306                 friend_type
 307                   = make_typename_type (ctype, name, class_type, tf_error);
 308             }
 309           else
 310             {
 311               decl = lookup_member (ctype, name, 0, true);
 312               if (!decl)
 313                 {
 314                   error ("%qT is not a member of %qT", name, ctype);
 315                   return;
 316                 }
 317               if (template_member_p && !DECL_CLASS_TEMPLATE_P (decl))
 318                 {
 319                   error ("%qT is not a member class template of %qT",
 320                          name, ctype);
 321                   error ("%q+D declared here", decl);
 322                   return;
 323                 }
 324               if (!template_member_p && (TREE_CODE (decl) != TYPE_DECL
 325                                          || !CLASS_TYPE_P (TREE_TYPE (decl))))
 326                 {
 327                   error ("%qT is not a nested class of %qT",
 328                          name, ctype);
 329                   error ("%q+D declared here", decl);
 330                   return;
 331                 }
 332
 333               friend_type = CLASSTYPE_TI_TEMPLATE (TREE_TYPE (decl));
 334             }
 335         }
 336     }
 337   else if (TREE_CODE (friend_type) == TEMPLATE_TYPE_PARM)
 338     {
 339       /* template <class T> friend class T; */
 340       error ("template parameter type %qT declared %<friend%>", friend_type);
 341       return;
 342     }
 343   else if (!CLASSTYPE_TEMPLATE_INFO (friend_type))
 344     {
 345       /* template <class T> friend class A; where A is not a template */
 346       error ("%q#T is not a template", friend_type);
 347       return;
 348     }
 349   else
 350     /* template <class T> friend class A; where A is a template */
 351     friend_type = CLASSTYPE_TI_TEMPLATE (friend_type);
 352
 353   if (friend_type == error_mark_node)
 354     return;
 355
 356   /* See if it is already a friend.  */
 357   for (classes = CLASSTYPE_FRIEND_CLASSES (type);
 358        classes;
 359        classes = TREE_CHAIN (classes))
 360     {
 361       tree probe = TREE_VALUE (classes);
 362
 363       if (TREE_CODE (friend_type) == TEMPLATE_DECL)
 364         {
 365           if (friend_type == probe)
 366             {
 367               if (complain)
 368                 warning (0, "%qD is already a friend of %qT", probe, type);
 369               break;
 370             }
 371         }
 372       else if (TREE_CODE (probe) != TEMPLATE_DECL)
 373         {
 374           if (same_type_p (probe, friend_type))
 375             {
 376               if (complain)
 377                 warning (0, "%qT is already a friend of %qT", probe, type);
 378               break;
 379             }
 380         }
 381     }
 382
 383   if (!classes)
 384     {
 385       maybe_add_class_template_decl_list (type, friend_type, /*friend_p=*/1);
 386
 387       CLASSTYPE_FRIEND_CLASSES (type)
 388         = tree_cons (NULL_TREE, friend_type, CLASSTYPE_FRIEND_CLASSES (type));
 389       if (TREE_CODE (friend_type) == TEMPLATE_DECL)
 390         friend_type = TREE_TYPE (friend_type);
 391       if (!uses_template_parms (type))
 392         CLASSTYPE_BEFRIENDING_CLASSES (friend_type)
 393           = tree_cons (NULL_TREE, type,
 394                        CLASSTYPE_BEFRIENDING_CLASSES (friend_type));
 395     }
 396 }
 397
 398 /* Record DECL (a FUNCTION_DECL) as a friend of the
 399    CURRENT_CLASS_TYPE.  If DECL is a member function, CTYPE is the
 400    class of which it is a member, as named in the friend declaration.
 401    DECLARATOR is the name of the friend.  FUNCDEF_FLAG is true if the
 402    friend declaration is a definition of the function.  FLAGS is as
 403    for grokclass fn.  */
 404
 405 tree
 406 do_friend (tree ctype, tree declarator, tree decl,
 407            tree attrlist, enum overload_flags flags,
 408            bool funcdef_flag)
 409 {
 410   gcc_assert (TREE_CODE (decl) == FUNCTION_DECL);
 411   gcc_assert (!ctype || IS_AGGR_TYPE (ctype));
 412
 413   /* Every decl that gets here is a friend of something.  */
 414   DECL_FRIEND_P (decl) = 1;
 415
 416   if (TREE_CODE (declarator) == TEMPLATE_ID_EXPR)
 417     {
 418       declarator = TREE_OPERAND (declarator, 0);
 419       if (is_overloaded_fn (declarator))
 420         declarator = DECL_NAME (get_first_fn (declarator));
 421     }
 422
 423   if (ctype)
 424     {
 425       /* CLASS_TEMPLATE_DEPTH counts the number of template headers for
 426          the enclosing class.  FRIEND_DEPTH counts the number of template
 427          headers used for this friend declaration.  TEMPLATE_MEMBER_P is
 428          true if a template header in FRIEND_DEPTH is intended for
 429          DECLARATOR.  For example, the code
 430
 431            template <class T> struct A {
 432              template <class U> struct B {
 433                template <class V> template <class W>
 434                  friend void C<V>::f(W);
 435              };
 436            };
 437
 438          will eventually give the following results
 439
 440          1. CLASS_TEMPLATE_DEPTH equals 2 (for `T' and `U').
 441          2. FRIEND_DEPTH equals 2 (for `V' and `W').
 442          3. TEMPLATE_MEMBER_P is true (for `W').  */
 443
 444       int class_template_depth = template_class_depth (current_class_type);
 445       int friend_depth = processing_template_decl - class_template_depth;
 446       /* We will figure this out later.  */
 447       bool template_member_p = false;
 448
 449       tree cname = TYPE_NAME (ctype);
 450       if (TREE_CODE (cname) == TYPE_DECL)
 451         cname = DECL_NAME (cname);
 452
 453       /* A method friend.  */
 454       if (flags == NO_SPECIAL && declarator == cname)
 455         DECL_CONSTRUCTOR_P (decl) = 1;
 456
 457       grokclassfn (ctype, decl, flags);
 458
 459       if (friend_depth)
 460         {
 461           if (!uses_template_parms_level (ctype, class_template_depth
 462                                                  + friend_depth))
 463             template_member_p = true;
 464         }
 465
 466       /* A nested class may declare a member of an enclosing class
 467          to be a friend, so we do lookup here even if CTYPE is in
 468          the process of being defined.  */
 469       if (class_template_depth
 470           || COMPLETE_TYPE_P (ctype)
 471           || (CLASS_TYPE_P (ctype) && TYPE_BEING_DEFINED (ctype)))
 472         {
 473           if (DECL_TEMPLATE_INFO (decl))
 474             /* DECL is a template specialization.  No need to
 475                build a new TEMPLATE_DECL.  */
 476             ;
 477           else if (class_template_depth)
 478             /* We rely on tsubst_friend_function to check the
 479                validity of the declaration later.  */
 480             decl = push_template_decl_real (decl, /*is_friend=*/true);
 481           else
 482             decl = check_classfn (ctype, decl,
 483                                   template_member_p
 484                                   ? current_template_parms
 485                                   : NULL_TREE);
 486
 487           if (template_member_p && decl && TREE_CODE (decl) == FUNCTION_DECL)
 488             decl = DECL_TI_TEMPLATE (decl);
 489
 490           if (decl)
 491             add_friend (current_class_type, decl, /*complain=*/true);
 492         }
 493       else
 494         error ("member %qD declared as friend before type %qT defined",
 495                   decl, ctype);
 496     }
 497   /* A global friend.
 498      @@ or possibly a friend from a base class ?!?  */
 499   else if (TREE_CODE (decl) == FUNCTION_DECL)
 500     {
 501       int is_friend_template = PROCESSING_REAL_TEMPLATE_DECL_P ();
 502
 503       /* Friends must all go through the overload machinery,
 504          even though they may not technically be overloaded.
 505
 506          Note that because classes all wind up being top-level
 507          in their scope, their friend wind up in top-level scope as well.  */
 508       if (funcdef_flag)
 509         SET_DECL_FRIEND_CONTEXT (decl, current_class_type);
 510
 511       if (! DECL_USE_TEMPLATE (decl))
 512         {
 513           /* We must check whether the decl refers to template
 514              arguments before push_template_decl_real adds a
 515              reference to the containing template class.  */
 516           int warn = (warn_nontemplate_friend
 517                       && ! funcdef_flag && ! is_friend_template
 518                       && current_template_parms
 519                       && uses_template_parms (decl));
 520
 521           if (is_friend_template
 522               || template_class_depth (current_class_type) != 0)
 523             /* We can't call pushdecl for a template class, since in
 524                general, such a declaration depends on template
 525                parameters.  Instead, we call pushdecl when the class
 526                is instantiated.  */
 527             decl = push_template_decl_real (decl, /*is_friend=*/true);
 528           else if (current_function_decl)
 529             {
 530               /* This must be a local class.  11.5p11:
 531
 532                  If a friend declaration appears in a local class (9.8) and
 533                  the name specified is an unqualified name, a prior
 534                  declaration is looked up without considering scopes that
 535                  are outside the innermost enclosing non-class scope. For a
 536                  friend function declaration, if there is no prior
 537                  declaration, the program is ill-formed.  */
 538               tree t = lookup_name_innermost_nonclass_level (DECL_NAME (decl));
 539               if (t)
 540                 decl = pushdecl_maybe_friend (decl, /*is_friend=*/true);
 541               else
 542                 {
 543                   error ("friend declaration %qD in local class without "
 544                          "prior declaration", decl);
 545                   return error_mark_node;
 546                 }
 547             }
 548           else
 549             {
 550               /* We can't use pushdecl, as we might be in a template
 551                  class specialization, and pushdecl will insert an
 552                  unqualified friend decl into the template parameter
 553                  scope, rather than the namespace containing it.  */
 554               tree ns = decl_namespace_context (decl);
 555
 556               push_nested_namespace (ns);
 557               decl = pushdecl_namespace_level (decl, /*is_friend=*/true);
 558               pop_nested_namespace (ns);
 559             }
 560
 561           if (warn)
 562             {
 563               static int explained;
 564               warning (OPT_Wnon_template_friend, "friend declaration "
 565                        "%q#D declares a non-template function", decl);
 566               if (! explained)
 567                 {
 568                   inform ("(if this is not what you intended, make sure "
 569                           "the function template has already been declared "
 570                           "and add <> after the function name here) ");
 571                   explained = 1;
 572                 }
 573             }
 574         }
 575
 576       if (decl == error_mark_node)
 577         return error_mark_node;
 578
 579       add_friend (current_class_type,
 580                   is_friend_template ? DECL_TI_TEMPLATE (decl) : decl,
 581                   /*complain=*/true);
 582       DECL_FRIEND_P (decl) = 1;
 583     }
 584
 585   /* Unfortunately, we have to handle attributes here.  Normally we would
 586      handle them in start_decl_1, but since this is a friend decl start_decl_1
 587      never gets to see it.  */
 588
 589   /* Set attributes here so if duplicate decl, will have proper attributes.  */
 590   cplus_decl_attributes (&decl, attrlist, 0);
 591
 592   return decl;
 593 }