1 /* Help friends in C++.
2 Copyright (C) 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005,
3 2007, 2008 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"
31 /* Friend data structures are described in cp-tree.h. */
33 /* Returns nonzero if SUPPLICANT is a friend of TYPE. */
36 is_friend (tree type
, tree supplicant
)
42 if (supplicant
== NULL_TREE
|| type
== NULL_TREE
)
45 declp
= DECL_P (supplicant
);
48 /* It's a function decl. */
50 tree list
= DECL_FRIENDLIST (TYPE_MAIN_DECL (type
));
51 tree name
= DECL_NAME (supplicant
);
53 for (; list
; list
= TREE_CHAIN (list
))
55 if (name
== FRIEND_NAME (list
))
57 tree friends
= FRIEND_DECLS (list
);
58 for (; friends
; friends
= TREE_CHAIN (friends
))
60 tree this_friend
= TREE_VALUE (friends
);
62 if (this_friend
== NULL_TREE
)
65 if (supplicant
== this_friend
)
68 if (is_specialization_of_friend (supplicant
, this_friend
))
78 if (same_type_p (supplicant
, type
))
81 list
= CLASSTYPE_FRIEND_CLASSES (TREE_TYPE (TYPE_MAIN_DECL (type
)));
82 for (; list
; list
= TREE_CHAIN (list
))
84 tree t
= TREE_VALUE (list
);
86 if (TREE_CODE (t
) == TEMPLATE_DECL
?
87 is_specialization_of_friend (TYPE_MAIN_DECL (supplicant
), t
) :
88 same_type_p (supplicant
, t
))
95 if (DECL_FUNCTION_MEMBER_P (supplicant
))
96 context
= DECL_CONTEXT (supplicant
);
102 if (TYPE_CLASS_SCOPE_P (supplicant
))
103 /* Nested classes get the same access as their enclosing types, as
104 per DR 45 (this is a change from the standard). */
105 context
= TYPE_CONTEXT (supplicant
);
107 /* Local classes have the same access as the enclosing function. */
108 context
= decl_function_context (TYPE_MAIN_DECL (supplicant
));
111 /* A namespace is not friend to anybody. */
112 if (context
&& TREE_CODE (context
) == NAMESPACE_DECL
)
116 return is_friend (type
, context
);
121 /* Add a new friend to the friends of the aggregate type TYPE.
122 DECL is the FUNCTION_DECL of the friend being added.
124 If COMPLAIN is true, warning about duplicate friend is issued.
125 We want to have this diagnostics during parsing but not
126 when a template is being instantiated. */
129 add_friend (tree type
, tree decl
, bool complain
)
136 if (decl
== error_mark_node
)
139 typedecl
= TYPE_MAIN_DECL (type
);
140 list
= DECL_FRIENDLIST (typedecl
);
141 name
= DECL_NAME (decl
);
142 type
= TREE_TYPE (typedecl
);
146 if (name
== FRIEND_NAME (list
))
148 tree friends
= FRIEND_DECLS (list
);
149 for (; friends
; friends
= TREE_CHAIN (friends
))
151 if (decl
== TREE_VALUE (friends
))
154 warning (0, "%qD is already a friend of class %qT",
160 maybe_add_class_template_decl_list (type
, decl
, /*friend_p=*/1);
162 TREE_VALUE (list
) = tree_cons (NULL_TREE
, decl
,
166 list
= TREE_CHAIN (list
);
169 ctx
= DECL_CONTEXT (decl
);
170 if (ctx
&& CLASS_TYPE_P (ctx
) && !uses_template_parms (ctx
))
171 perform_or_defer_access_check (TYPE_BINFO (ctx
), decl
, decl
);
173 maybe_add_class_template_decl_list (type
, decl
, /*friend_p=*/1);
175 DECL_FRIENDLIST (typedecl
)
176 = tree_cons (DECL_NAME (decl
), build_tree_list (NULL_TREE
, decl
),
177 DECL_FRIENDLIST (typedecl
));
178 if (!uses_template_parms (type
))
179 DECL_BEFRIENDING_CLASSES (decl
)
180 = tree_cons (NULL_TREE
, type
,
181 DECL_BEFRIENDING_CLASSES (decl
));
184 /* Make FRIEND_TYPE a friend class to TYPE. If FRIEND_TYPE has already
185 been defined, we make all of its member functions friends of
186 TYPE. If not, we make it a pending friend, which can later be added
187 when its definition is seen. If a type is defined, then its TYPE_DECL's
188 DECL_UNDEFINED_FRIENDS contains a (possibly empty) list of friend
189 classes that are not defined. If a type has not yet been defined,
190 then the DECL_WAITING_FRIENDS contains a list of types
191 waiting to make it their friend. Note that these two can both
192 be in use at the same time!
194 If COMPLAIN is true, warning about duplicate friend is issued.
195 We want to have this diagnostics during parsing but not
196 when a template is being instantiated. */
199 make_friend_class (tree type
, tree friend_type
, bool complain
)
203 /* CLASS_TEMPLATE_DEPTH counts the number of template headers for
204 the enclosing class. FRIEND_DEPTH counts the number of template
205 headers used for this friend declaration. TEMPLATE_MEMBER_P,
206 defined inside the `if' block for TYPENAME_TYPE case, is true if
207 a template header in FRIEND_DEPTH is intended for DECLARATOR.
208 For example, the code
210 template <class T> struct A {
211 template <class U> struct B {
212 template <class V> template <class W>
213 friend class C<V>::D;
217 will eventually give the following results
219 1. CLASS_TEMPLATE_DEPTH equals 2 (for `T' and `U').
220 2. FRIEND_DEPTH equals 2 (for `V' and `W').
221 3. TEMPLATE_MEMBER_P is true (for `W').
223 The friend is a template friend iff FRIEND_DEPTH is nonzero. */
225 int class_template_depth
= template_class_depth (type
);
226 int friend_depth
= processing_template_decl
- class_template_depth
;
228 if (! MAYBE_CLASS_TYPE_P (friend_type
))
230 error ("invalid type %qT declared %<friend%>", friend_type
);
235 /* If the TYPE is a template then it makes sense for it to be
236 friends with itself; this means that each instantiation is
237 friends with all other instantiations. */
239 if (CLASS_TYPE_P (friend_type
)
240 && CLASSTYPE_TEMPLATE_SPECIALIZATION (friend_type
)
241 && uses_template_parms (friend_type
))
244 Friend declarations shall not declare partial
246 error ("partial specialization %qT declared %<friend%>",
251 else if (same_type_p (type
, friend_type
))
254 warning (0, "class %qT is implicitly friends with itself",
261 A friend of a class or class template can be a function or
262 class template, a specialization of a function template or
263 class template, or an ordinary (nontemplate) function or
267 else if (TREE_CODE (friend_type
) == TYPENAME_TYPE
)
269 if (TREE_CODE (TYPENAME_TYPE_FULLNAME (friend_type
))
272 /* template <class U> friend class T::X<U>; */
274 Friend declarations shall not declare partial
276 error ("partial specialization %qT declared %<friend%>",
282 /* We will figure this out later. */
283 bool template_member_p
= false;
285 tree ctype
= TYPE_CONTEXT (friend_type
);
286 tree name
= TYPE_IDENTIFIER (friend_type
);
289 if (!uses_template_parms_level (ctype
, class_template_depth
291 template_member_p
= true;
293 if (class_template_depth
)
295 /* We rely on tsubst_friend_class to check the
296 validity of the declaration later. */
297 if (template_member_p
)
299 = make_unbound_class_template (ctype
,
301 current_template_parms
,
305 = make_typename_type (ctype
, name
, class_type
, tf_error
);
309 decl
= lookup_member (ctype
, name
, 0, true);
312 error ("%qT is not a member of %qT", name
, ctype
);
315 if (template_member_p
&& !DECL_CLASS_TEMPLATE_P (decl
))
317 error ("%qT is not a member class template of %qT",
319 error ("%q+D declared here", decl
);
322 if (!template_member_p
&& (TREE_CODE (decl
) != TYPE_DECL
323 || !CLASS_TYPE_P (TREE_TYPE (decl
))))
325 error ("%qT is not a nested class of %qT",
327 error ("%q+D declared here", decl
);
331 friend_type
= CLASSTYPE_TI_TEMPLATE (TREE_TYPE (decl
));
335 else if (TREE_CODE (friend_type
) == TEMPLATE_TYPE_PARM
)
337 /* template <class T> friend class T; */
338 error ("template parameter type %qT declared %<friend%>", friend_type
);
341 else if (!CLASSTYPE_TEMPLATE_INFO (friend_type
))
343 /* template <class T> friend class A; where A is not a template */
344 error ("%q#T is not a template", friend_type
);
348 /* template <class T> friend class A; where A is a template */
349 friend_type
= CLASSTYPE_TI_TEMPLATE (friend_type
);
351 if (friend_type
== error_mark_node
)
354 /* See if it is already a friend. */
355 for (classes
= CLASSTYPE_FRIEND_CLASSES (type
);
357 classes
= TREE_CHAIN (classes
))
359 tree probe
= TREE_VALUE (classes
);
361 if (TREE_CODE (friend_type
) == TEMPLATE_DECL
)
363 if (friend_type
== probe
)
366 warning (0, "%qD is already a friend of %qT", probe
, type
);
370 else if (TREE_CODE (probe
) != TEMPLATE_DECL
)
372 if (same_type_p (probe
, friend_type
))
375 warning (0, "%qT is already a friend of %qT", probe
, type
);
383 maybe_add_class_template_decl_list (type
, friend_type
, /*friend_p=*/1);
385 CLASSTYPE_FRIEND_CLASSES (type
)
386 = tree_cons (NULL_TREE
, friend_type
, CLASSTYPE_FRIEND_CLASSES (type
));
387 if (TREE_CODE (friend_type
) == TEMPLATE_DECL
)
388 friend_type
= TREE_TYPE (friend_type
);
389 if (!uses_template_parms (type
))
390 CLASSTYPE_BEFRIENDING_CLASSES (friend_type
)
391 = tree_cons (NULL_TREE
, type
,
392 CLASSTYPE_BEFRIENDING_CLASSES (friend_type
));
396 /* Record DECL (a FUNCTION_DECL) as a friend of the
397 CURRENT_CLASS_TYPE. If DECL is a member function, CTYPE is the
398 class of which it is a member, as named in the friend declaration.
399 DECLARATOR is the name of the friend. FUNCDEF_FLAG is true if the
400 friend declaration is a definition of the function. FLAGS is as
404 do_friend (tree ctype
, tree declarator
, tree decl
,
405 tree attrlist
, enum overload_flags flags
,
408 gcc_assert (TREE_CODE (decl
) == FUNCTION_DECL
);
409 gcc_assert (!ctype
|| MAYBE_CLASS_TYPE_P (ctype
));
411 /* Every decl that gets here is a friend of something. */
412 DECL_FRIEND_P (decl
) = 1;
414 /* Unfortunately, we have to handle attributes here. Normally we would
415 handle them in start_decl_1, but since this is a friend decl start_decl_1
416 never gets to see it. */
418 /* Set attributes here so if duplicate decl, will have proper attributes. */
419 cplus_decl_attributes (&decl
, attrlist
, 0);
421 if (TREE_CODE (declarator
) == TEMPLATE_ID_EXPR
)
423 declarator
= TREE_OPERAND (declarator
, 0);
424 if (is_overloaded_fn (declarator
))
425 declarator
= DECL_NAME (get_first_fn (declarator
));
430 /* CLASS_TEMPLATE_DEPTH counts the number of template headers for
431 the enclosing class. FRIEND_DEPTH counts the number of template
432 headers used for this friend declaration. TEMPLATE_MEMBER_P is
433 true if a template header in FRIEND_DEPTH is intended for
434 DECLARATOR. For example, the code
436 template <class T> struct A {
437 template <class U> struct B {
438 template <class V> template <class W>
439 friend void C<V>::f(W);
443 will eventually give the following results
445 1. CLASS_TEMPLATE_DEPTH equals 2 (for `T' and `U').
446 2. FRIEND_DEPTH equals 2 (for `V' and `W').
447 3. TEMPLATE_MEMBER_P is true (for `W'). */
449 int class_template_depth
= template_class_depth (current_class_type
);
450 int friend_depth
= processing_template_decl
- class_template_depth
;
451 /* We will figure this out later. */
452 bool template_member_p
= false;
454 tree cname
= TYPE_NAME (ctype
);
455 if (TREE_CODE (cname
) == TYPE_DECL
)
456 cname
= DECL_NAME (cname
);
458 /* A method friend. */
459 if (flags
== NO_SPECIAL
&& declarator
== cname
)
460 DECL_CONSTRUCTOR_P (decl
) = 1;
462 grokclassfn (ctype
, decl
, flags
);
466 if (!uses_template_parms_level (ctype
, class_template_depth
468 template_member_p
= true;
471 /* A nested class may declare a member of an enclosing class
472 to be a friend, so we do lookup here even if CTYPE is in
473 the process of being defined. */
474 if (class_template_depth
475 || COMPLETE_TYPE_P (ctype
)
476 || (CLASS_TYPE_P (ctype
) && TYPE_BEING_DEFINED (ctype
)))
478 if (DECL_TEMPLATE_INFO (decl
))
479 /* DECL is a template specialization. No need to
480 build a new TEMPLATE_DECL. */
482 else if (class_template_depth
)
483 /* We rely on tsubst_friend_function to check the
484 validity of the declaration later. */
485 decl
= push_template_decl_real (decl
, /*is_friend=*/true);
487 decl
= check_classfn (ctype
, decl
,
489 ? current_template_parms
492 if (template_member_p
&& decl
&& TREE_CODE (decl
) == FUNCTION_DECL
)
493 decl
= DECL_TI_TEMPLATE (decl
);
496 add_friend (current_class_type
, decl
, /*complain=*/true);
499 error ("member %qD declared as friend before type %qT defined",
503 @@ or possibly a friend from a base class ?!? */
504 else if (TREE_CODE (decl
) == FUNCTION_DECL
)
506 int is_friend_template
= PROCESSING_REAL_TEMPLATE_DECL_P ();
508 /* Friends must all go through the overload machinery,
509 even though they may not technically be overloaded.
511 Note that because classes all wind up being top-level
512 in their scope, their friend wind up in top-level scope as well. */
514 SET_DECL_FRIEND_CONTEXT (decl
, current_class_type
);
516 if (! DECL_USE_TEMPLATE (decl
))
518 /* We must check whether the decl refers to template
519 arguments before push_template_decl_real adds a
520 reference to the containing template class. */
521 int warn
= (warn_nontemplate_friend
522 && ! funcdef_flag
&& ! is_friend_template
523 && current_template_parms
524 && uses_template_parms (decl
));
526 if (is_friend_template
527 || template_class_depth (current_class_type
) != 0)
528 /* We can't call pushdecl for a template class, since in
529 general, such a declaration depends on template
530 parameters. Instead, we call pushdecl when the class
532 decl
= push_template_decl_real (decl
, /*is_friend=*/true);
533 else if (current_function_decl
)
535 /* This must be a local class. 11.5p11:
537 If a friend declaration appears in a local class (9.8) and
538 the name specified is an unqualified name, a prior
539 declaration is looked up without considering scopes that
540 are outside the innermost enclosing non-class scope. For a
541 friend function declaration, if there is no prior
542 declaration, the program is ill-formed. */
543 tree t
= lookup_name_innermost_nonclass_level (DECL_NAME (decl
));
545 decl
= pushdecl_maybe_friend (decl
, /*is_friend=*/true);
548 error ("friend declaration %qD in local class without "
549 "prior declaration", decl
);
550 return error_mark_node
;
555 /* We can't use pushdecl, as we might be in a template
556 class specialization, and pushdecl will insert an
557 unqualified friend decl into the template parameter
558 scope, rather than the namespace containing it. */
559 tree ns
= decl_namespace_context (decl
);
561 push_nested_namespace (ns
);
562 decl
= pushdecl_namespace_level (decl
, /*is_friend=*/true);
563 pop_nested_namespace (ns
);
568 static int explained
;
571 warned
= warning (OPT_Wnon_template_friend
, "friend declaration "
572 "%q#D declares a non-template function", decl
);
573 if (! explained
&& warned
)
575 inform (input_location
, "(if this is not what you intended, make sure "
576 "the function template has already been declared "
577 "and add <> after the function name here) ");
583 if (decl
== error_mark_node
)
584 return error_mark_node
;
586 add_friend (current_class_type
,
587 is_friend_template
? DECL_TI_TEMPLATE (decl
) : decl
,
589 DECL_FRIEND_P (decl
) = 1;