1 /* Help friends in C++.
2 Copyright (C) 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005,
3 2007, 2008, 2010 Free Software Foundation, Inc.
5 This file is part of GCC.
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)
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.
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/>. */
23 #include "coretypes.h"
30 /* Friend data structures are described in cp-tree.h. */
32 /* Returns nonzero if SUPPLICANT is a friend of TYPE. */
35 is_friend (tree type, tree supplicant)
41 if (supplicant == NULL_TREE || type == NULL_TREE)
44 declp = DECL_P (supplicant);
47 /* It's a function decl. */
49 tree list = DECL_FRIENDLIST (TYPE_MAIN_DECL (type));
50 tree name = DECL_NAME (supplicant);
52 for (; list ; list = TREE_CHAIN (list))
54 if (name == FRIEND_NAME (list))
56 tree friends = FRIEND_DECLS (list);
57 for (; friends ; friends = TREE_CHAIN (friends))
59 tree this_friend = TREE_VALUE (friends);
61 if (this_friend == NULL_TREE)
64 if (supplicant == this_friend)
67 if (is_specialization_of_friend (supplicant, this_friend))
77 if (same_type_p (supplicant, type))
80 list = CLASSTYPE_FRIEND_CLASSES (TREE_TYPE (TYPE_MAIN_DECL (type)));
81 for (; list ; list = TREE_CHAIN (list))
83 tree t = TREE_VALUE (list);
85 if (TREE_CODE (t) == TEMPLATE_DECL ?
86 is_specialization_of_friend (TYPE_MAIN_DECL (supplicant), t) :
87 same_type_p (supplicant, t))
94 if (DECL_FUNCTION_MEMBER_P (supplicant))
95 context = DECL_CONTEXT (supplicant);
101 if (TYPE_CLASS_SCOPE_P (supplicant))
102 /* Nested classes get the same access as their enclosing types, as
103 per DR 45 (this is a change from the standard). */
104 context = TYPE_CONTEXT (supplicant);
106 /* Local classes have the same access as the enclosing function. */
107 context = decl_function_context (TYPE_MAIN_DECL (supplicant));
110 /* A namespace is not friend to anybody. */
111 if (context && TREE_CODE (context) == NAMESPACE_DECL)
115 return is_friend (type, context);
120 /* Add a new friend to the friends of the aggregate type TYPE.
121 DECL is the FUNCTION_DECL of the friend being added.
123 If COMPLAIN is true, warning about duplicate friend is issued.
124 We want to have this diagnostics during parsing but not
125 when a template is being instantiated. */
128 add_friend (tree type, tree decl, bool complain)
135 if (decl == error_mark_node)
138 typedecl = TYPE_MAIN_DECL (type);
139 list = DECL_FRIENDLIST (typedecl);
140 name = DECL_NAME (decl);
141 type = TREE_TYPE (typedecl);
145 if (name == FRIEND_NAME (list))
147 tree friends = FRIEND_DECLS (list);
148 for (; friends ; friends = TREE_CHAIN (friends))
150 if (decl == TREE_VALUE (friends))
153 warning (0, "%qD is already a friend of class %qT",
159 maybe_add_class_template_decl_list (type, decl, /*friend_p=*/1);
161 TREE_VALUE (list) = tree_cons (NULL_TREE, decl,
165 list = TREE_CHAIN (list);
168 ctx = DECL_CONTEXT (decl);
169 if (ctx && CLASS_TYPE_P (ctx) && !uses_template_parms (ctx))
170 perform_or_defer_access_check (TYPE_BINFO (ctx), decl, decl);
172 maybe_add_class_template_decl_list (type, decl, /*friend_p=*/1);
174 DECL_FRIENDLIST (typedecl)
175 = tree_cons (DECL_NAME (decl), build_tree_list (NULL_TREE, decl),
176 DECL_FRIENDLIST (typedecl));
177 if (!uses_template_parms (type))
178 DECL_BEFRIENDING_CLASSES (decl)
179 = tree_cons (NULL_TREE, type,
180 DECL_BEFRIENDING_CLASSES (decl));
183 /* Make FRIEND_TYPE a friend class to TYPE. If FRIEND_TYPE has already
184 been defined, we make all of its member functions friends of
185 TYPE. If not, we make it a pending friend, which can later be added
186 when its definition is seen. If a type is defined, then its TYPE_DECL's
187 DECL_UNDEFINED_FRIENDS contains a (possibly empty) list of friend
188 classes that are not defined. If a type has not yet been defined,
189 then the DECL_WAITING_FRIENDS contains a list of types
190 waiting to make it their friend. Note that these two can both
191 be in use at the same time!
193 If COMPLAIN is true, warning about duplicate friend is issued.
194 We want to have this diagnostics during parsing but not
195 when a template is being instantiated. */
198 make_friend_class (tree type, tree friend_type, bool complain)
202 /* CLASS_TEMPLATE_DEPTH counts the number of template headers for
203 the enclosing class. FRIEND_DEPTH counts the number of template
204 headers used for this friend declaration. TEMPLATE_MEMBER_P,
205 defined inside the `if' block for TYPENAME_TYPE case, is true if
206 a template header in FRIEND_DEPTH is intended for DECLARATOR.
207 For example, the code
209 template <class T> struct A {
210 template <class U> struct B {
211 template <class V> template <class W>
212 friend class C<V>::D;
216 will eventually give the following results
218 1. CLASS_TEMPLATE_DEPTH equals 2 (for `T' and `U').
219 2. FRIEND_DEPTH equals 2 (for `V' and `W').
220 3. TEMPLATE_MEMBER_P is true (for `W').
222 The friend is a template friend iff FRIEND_DEPTH is nonzero. */
224 int class_template_depth = template_class_depth (type);
225 int friend_depth = processing_template_decl - class_template_depth;
227 if (! MAYBE_CLASS_TYPE_P (friend_type))
229 /* N1791: If the type specifier in a friend declaration designates a
230 (possibly cv-qualified) class type, that class is declared as a
231 friend; otherwise, the friend declaration is ignored.
233 So don't complain in C++0x mode. */
234 if (cxx_dialect < cxx0x)
235 pedwarn (input_location, complain ? 0 : OPT_pedantic,
236 "invalid type %qT declared %<friend%>", friend_type);
241 /* If the TYPE is a template then it makes sense for it to be
242 friends with itself; this means that each instantiation is
243 friends with all other instantiations. */
245 if (CLASS_TYPE_P (friend_type)
246 && CLASSTYPE_TEMPLATE_SPECIALIZATION (friend_type)
247 && uses_template_parms (friend_type))
250 Friend declarations shall not declare partial
252 error ("partial specialization %qT declared %<friend%>",
257 else if (same_type_p (type, friend_type))
260 warning (0, "class %qT is implicitly friends with itself",
267 A friend of a class or class template can be a function or
268 class template, a specialization of a function template or
269 class template, or an ordinary (nontemplate) function or
273 else if (TREE_CODE (friend_type) == TYPENAME_TYPE)
275 if (TREE_CODE (TYPENAME_TYPE_FULLNAME (friend_type))
278 /* template <class U> friend class T::X<U>; */
280 Friend declarations shall not declare partial
282 error ("partial specialization %qT declared %<friend%>",
288 /* We will figure this out later. */
289 bool template_member_p = false;
291 tree ctype = TYPE_CONTEXT (friend_type);
292 tree name = TYPE_IDENTIFIER (friend_type);
295 if (!uses_template_parms_level (ctype, class_template_depth
297 template_member_p = true;
299 if (class_template_depth)
301 /* We rely on tsubst_friend_class to check the
302 validity of the declaration later. */
303 if (template_member_p)
305 = make_unbound_class_template (ctype,
307 current_template_parms,
311 = make_typename_type (ctype, name, class_type, tf_error);
315 decl = lookup_member (ctype, name, 0, true);
318 error ("%qT is not a member of %qT", name, ctype);
321 if (template_member_p && !DECL_CLASS_TEMPLATE_P (decl))
323 error ("%qT is not a member class template of %qT",
325 error ("%q+D declared here", decl);
328 if (!template_member_p && (TREE_CODE (decl) != TYPE_DECL
329 || !CLASS_TYPE_P (TREE_TYPE (decl))))
331 error ("%qT is not a nested class of %qT",
333 error ("%q+D declared here", decl);
337 friend_type = CLASSTYPE_TI_TEMPLATE (TREE_TYPE (decl));
341 else if (TREE_CODE (friend_type) == TEMPLATE_TYPE_PARM)
343 /* template <class T> friend class T; */
344 error ("template parameter type %qT declared %<friend%>", friend_type);
347 else if (!CLASSTYPE_TEMPLATE_INFO (friend_type))
349 /* template <class T> friend class A; where A is not a template */
350 error ("%q#T is not a template", friend_type);
354 /* template <class T> friend class A; where A is a template */
355 friend_type = CLASSTYPE_TI_TEMPLATE (friend_type);
357 if (friend_type == error_mark_node)
360 /* See if it is already a friend. */
361 for (classes = CLASSTYPE_FRIEND_CLASSES (type);
363 classes = TREE_CHAIN (classes))
365 tree probe = TREE_VALUE (classes);
367 if (TREE_CODE (friend_type) == TEMPLATE_DECL)
369 if (friend_type == probe)
372 warning (0, "%qD is already a friend of %qT", probe, type);
376 else if (TREE_CODE (probe) != TEMPLATE_DECL)
378 if (same_type_p (probe, friend_type))
381 warning (0, "%qT is already a friend of %qT", probe, type);
389 maybe_add_class_template_decl_list (type, friend_type, /*friend_p=*/1);
391 CLASSTYPE_FRIEND_CLASSES (type)
392 = tree_cons (NULL_TREE, friend_type, CLASSTYPE_FRIEND_CLASSES (type));
393 if (TREE_CODE (friend_type) == TEMPLATE_DECL)
394 friend_type = TREE_TYPE (friend_type);
395 if (!uses_template_parms (type))
396 CLASSTYPE_BEFRIENDING_CLASSES (friend_type)
397 = tree_cons (NULL_TREE, type,
398 CLASSTYPE_BEFRIENDING_CLASSES (friend_type));
402 /* Record DECL (a FUNCTION_DECL) as a friend of the
403 CURRENT_CLASS_TYPE. If DECL is a member function, CTYPE is the
404 class of which it is a member, as named in the friend declaration.
405 DECLARATOR is the name of the friend. FUNCDEF_FLAG is true if the
406 friend declaration is a definition of the function. FLAGS is as
410 do_friend (tree ctype, tree declarator, tree decl,
411 tree attrlist, enum overload_flags flags,
414 gcc_assert (TREE_CODE (decl) == FUNCTION_DECL);
415 gcc_assert (!ctype || MAYBE_CLASS_TYPE_P (ctype));
417 /* Every decl that gets here is a friend of something. */
418 DECL_FRIEND_P (decl) = 1;
420 /* Unfortunately, we have to handle attributes here. Normally we would
421 handle them in start_decl_1, but since this is a friend decl start_decl_1
422 never gets to see it. */
424 /* Set attributes here so if duplicate decl, will have proper attributes. */
425 cplus_decl_attributes (&decl, attrlist, 0);
427 if (TREE_CODE (declarator) == TEMPLATE_ID_EXPR)
429 declarator = TREE_OPERAND (declarator, 0);
430 if (is_overloaded_fn (declarator))
431 declarator = DECL_NAME (get_first_fn (declarator));
436 /* CLASS_TEMPLATE_DEPTH counts the number of template headers for
437 the enclosing class. FRIEND_DEPTH counts the number of template
438 headers used for this friend declaration. TEMPLATE_MEMBER_P is
439 true if a template header in FRIEND_DEPTH is intended for
440 DECLARATOR. For example, the code
442 template <class T> struct A {
443 template <class U> struct B {
444 template <class V> template <class W>
445 friend void C<V>::f(W);
449 will eventually give the following results
451 1. CLASS_TEMPLATE_DEPTH equals 2 (for `T' and `U').
452 2. FRIEND_DEPTH equals 2 (for `V' and `W').
453 3. TEMPLATE_MEMBER_P is true (for `W'). */
455 int class_template_depth = template_class_depth (current_class_type);
456 int friend_depth = processing_template_decl - class_template_depth;
457 /* We will figure this out later. */
458 bool template_member_p = false;
460 tree cname = TYPE_NAME (ctype);
461 if (TREE_CODE (cname) == TYPE_DECL)
462 cname = DECL_NAME (cname);
464 /* A method friend. */
465 if (flags == NO_SPECIAL && declarator == cname)
466 DECL_CONSTRUCTOR_P (decl) = 1;
468 grokclassfn (ctype, decl, flags);
472 if (!uses_template_parms_level (ctype, class_template_depth
474 template_member_p = true;
477 /* A nested class may declare a member of an enclosing class
478 to be a friend, so we do lookup here even if CTYPE is in
479 the process of being defined. */
480 if (class_template_depth
481 || COMPLETE_TYPE_P (ctype)
482 || (CLASS_TYPE_P (ctype) && TYPE_BEING_DEFINED (ctype)))
484 if (DECL_TEMPLATE_INFO (decl))
485 /* DECL is a template specialization. No need to
486 build a new TEMPLATE_DECL. */
488 else if (class_template_depth)
489 /* We rely on tsubst_friend_function to check the
490 validity of the declaration later. */
491 decl = push_template_decl_real (decl, /*is_friend=*/true);
493 decl = check_classfn (ctype, decl,
495 ? current_template_parms
498 if (template_member_p && decl && TREE_CODE (decl) == FUNCTION_DECL)
499 decl = DECL_TI_TEMPLATE (decl);
502 add_friend (current_class_type, decl, /*complain=*/true);
505 error ("member %qD declared as friend before type %qT defined",
509 @@ or possibly a friend from a base class ?!? */
510 else if (TREE_CODE (decl) == FUNCTION_DECL)
512 int is_friend_template = PROCESSING_REAL_TEMPLATE_DECL_P ();
514 /* Friends must all go through the overload machinery,
515 even though they may not technically be overloaded.
517 Note that because classes all wind up being top-level
518 in their scope, their friend wind up in top-level scope as well. */
520 SET_DECL_FRIEND_CONTEXT (decl, current_class_type);
522 if (! DECL_USE_TEMPLATE (decl))
524 /* We must check whether the decl refers to template
525 arguments before push_template_decl_real adds a
526 reference to the containing template class. */
527 int warn = (warn_nontemplate_friend
528 && ! funcdef_flag && ! is_friend_template
529 && current_template_parms
530 && uses_template_parms (decl));
532 if (is_friend_template
533 || template_class_depth (current_class_type) != 0)
534 /* We can't call pushdecl for a template class, since in
535 general, such a declaration depends on template
536 parameters. Instead, we call pushdecl when the class
538 decl = push_template_decl_real (decl, /*is_friend=*/true);
539 else if (current_function_decl)
541 /* This must be a local class. 11.5p11:
543 If a friend declaration appears in a local class (9.8) and
544 the name specified is an unqualified name, a prior
545 declaration is looked up without considering scopes that
546 are outside the innermost enclosing non-class scope. For a
547 friend function declaration, if there is no prior
548 declaration, the program is ill-formed. */
549 tree t = lookup_name_innermost_nonclass_level (DECL_NAME (decl));
551 decl = pushdecl_maybe_friend (decl, /*is_friend=*/true);
554 error ("friend declaration %qD in local class without "
555 "prior declaration", decl);
556 return error_mark_node;
561 /* We can't use pushdecl, as we might be in a template
562 class specialization, and pushdecl will insert an
563 unqualified friend decl into the template parameter
564 scope, rather than the namespace containing it. */
565 tree ns = decl_namespace_context (decl);
567 push_nested_namespace (ns);
568 decl = pushdecl_namespace_level (decl, /*is_friend=*/true);
569 pop_nested_namespace (ns);
574 static int explained;
577 warned = warning (OPT_Wnon_template_friend, "friend declaration "
578 "%q#D declares a non-template function", decl);
579 if (! explained && warned)
581 inform (input_location, "(if this is not what you intended, make sure "
582 "the function template has already been declared "
583 "and add <> after the function name here) ");
589 if (decl == error_mark_node)
590 return error_mark_node;
592 add_friend (current_class_type,
593 is_friend_template ? DECL_TI_TEMPLATE (decl) : decl,
595 DECL_FRIEND_P (decl) = 1;