1 /* Help friends in C++. 2 Copyright (C) 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005, 3 2007, 2008, 2010, 2011 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 "cp-tree.h" 27 #include "flags.h" 28 #include "output.h" 29 30 /* Friend data structures are described in cp-tree.h. */ 31 32 /* Returns nonzero if SUPPLICANT is a friend of TYPE. */ 33 34 int 35 is_friend (tree type, tree supplicant) 36 { 37 int declp; 38 tree list; 39 tree context; 40 41 if (supplicant == NULL_TREE || type == NULL_TREE) 42 return 0; 43 44 declp = DECL_P (supplicant); 45 46 if (declp) 47 /* It's a function decl. */ 48 { 49 tree list = DECL_FRIENDLIST (TYPE_MAIN_DECL (type)); 50 tree name = DECL_NAME (supplicant); 51 52 for (; list ; list = TREE_CHAIN (list)) 53 { 54 if (name == FRIEND_NAME (list)) 55 { 56 tree friends = FRIEND_DECLS (list); 57 for (; friends ; friends = TREE_CHAIN (friends)) 58 { 59 tree this_friend = TREE_VALUE (friends); 60 61 if (this_friend == NULL_TREE) 62 continue; 63 64 if (supplicant == this_friend) 65 return 1; 66 67 if (is_specialization_of_friend (supplicant, this_friend)) 68 return 1; 69 } 70 break; 71 } 72 } 73 } 74 else 75 /* It's a type. */ 76 { 77 if (same_type_p (supplicant, type)) 78 return 1; 79 80 list = CLASSTYPE_FRIEND_CLASSES (TREE_TYPE (TYPE_MAIN_DECL (type))); 81 for (; list ; list = TREE_CHAIN (list)) 82 { 83 tree t = TREE_VALUE (list); 84 85 if (TREE_CODE (t) == TEMPLATE_DECL ? 86 is_specialization_of_friend (TYPE_MAIN_DECL (supplicant), t) : 87 same_type_p (supplicant, t)) 88 return 1; 89 } 90 } 91 92 if (declp) 93 { 94 if (DECL_FUNCTION_MEMBER_P (supplicant)) 95 context = DECL_CONTEXT (supplicant); 96 else 97 context = NULL_TREE; 98 } 99 else 100 { 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); 105 else 106 /* Local classes have the same access as the enclosing function. */ 107 context = decl_function_context (TYPE_MAIN_DECL (supplicant)); 108 } 109 110 /* A namespace is not friend to anybody. */ 111 if (context && TREE_CODE (context) == NAMESPACE_DECL) 112 context = NULL_TREE; 113 114 if (context) 115 return is_friend (type, context); 116 117 return 0; 118 } 119 120 /* Add a new friend to the friends of the aggregate type TYPE. 121 DECL is the FUNCTION_DECL of the friend being added. 122 123 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. */ 126 127 void 128 add_friend (tree type, tree decl, bool complain) 129 { 130 tree typedecl; 131 tree list; 132 tree name; 133 tree ctx; 134 135 if (decl == error_mark_node) 136 return; 137 138 typedecl = TYPE_MAIN_DECL (type); 139 list = DECL_FRIENDLIST (typedecl); 140 name = DECL_NAME (decl); 141 type = TREE_TYPE (typedecl); 142 143 while (list) 144 { 145 if (name == FRIEND_NAME (list)) 146 { 147 tree friends = FRIEND_DECLS (list); 148 for (; friends ; friends = TREE_CHAIN (friends)) 149 { 150 if (decl == TREE_VALUE (friends)) 151 { 152 if (complain) 153 warning (0, "%qD is already a friend of class %qT", 154 decl, type); 155 return; 156 } 157 } 158 159 maybe_add_class_template_decl_list (type, decl, /*friend_p=*/1); 160 161 TREE_VALUE (list) = tree_cons (NULL_TREE, decl, 162 TREE_VALUE (list)); 163 return; 164 } 165 list = TREE_CHAIN (list); 166 } 167 168 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); 171 172 maybe_add_class_template_decl_list (type, decl, /*friend_p=*/1); 173 174 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)); 181 } 182 183 /* 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! 192 193 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. */ 196 197 void 198 make_friend_class (tree type, tree friend_type, bool complain) 199 { 200 tree classes; 201 202 /* 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 208 209 template <class T> struct A { 210 template <class U> struct B { 211 template <class V> template <class W> 212 friend class C<V>::D; 213 }; 214 }; 215 216 will eventually give the following results 217 218 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'). 221 222 The friend is a template friend iff FRIEND_DEPTH is nonzero. */ 223 224 int class_template_depth = template_class_depth (type); 225 int friend_depth = processing_template_decl - class_template_depth; 226 227 if (! MAYBE_CLASS_TYPE_P (friend_type)) 228 { 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. 232 233 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); 237 return; 238 } 239 240 friend_type = cv_unqualified (friend_type); 241 242 if (friend_depth) 243 /* If the TYPE is a template then it makes sense for it to be 244 friends with itself; this means that each instantiation is 245 friends with all other instantiations. */ 246 { 247 if (CLASS_TYPE_P (friend_type) 248 && CLASSTYPE_TEMPLATE_SPECIALIZATION (friend_type) 249 && uses_template_parms (friend_type)) 250 { 251 /* [temp.friend] 252 Friend declarations shall not declare partial 253 specializations. */ 254 error ("partial specialization %qT declared %<friend%>", 255 friend_type); 256 return; 257 } 258 } 259 else if (same_type_p (type, friend_type)) 260 { 261 if (complain) 262 warning (0, "class %qT is implicitly friends with itself", 263 type); 264 return; 265 } 266 267 /* [temp.friend] 268 269 A friend of a class or class template can be a function or 270 class template, a specialization of a function template or 271 class template, or an ordinary (nontemplate) function or 272 class. */ 273 if (!friend_depth) 274 ;/* ok */ 275 else if (TREE_CODE (friend_type) == TYPENAME_TYPE) 276 { 277 if (TREE_CODE (TYPENAME_TYPE_FULLNAME (friend_type)) 278 == TEMPLATE_ID_EXPR) 279 { 280 /* template <class U> friend class T::X<U>; */ 281 /* [temp.friend] 282 Friend declarations shall not declare partial 283 specializations. */ 284 error ("partial specialization %qT declared %<friend%>", 285 friend_type); 286 return; 287 } 288 else 289 { 290 /* We will figure this out later. */ 291 bool template_member_p = false; 292 293 tree ctype = TYPE_CONTEXT (friend_type); 294 tree name = TYPE_IDENTIFIER (friend_type); 295 tree decl; 296 297 if (!uses_template_parms_level (ctype, class_template_depth 298 + friend_depth)) 299 template_member_p = true; 300 301 if (class_template_depth) 302 { 303 /* We rely on tsubst_friend_class to check the 304 validity of the declaration later. */ 305 if (template_member_p) 306 friend_type 307 = make_unbound_class_template (ctype, 308 name, 309 current_template_parms, 310 tf_error); 311 else 312 friend_type 313 = make_typename_type (ctype, name, class_type, tf_error); 314 } 315 else 316 { 317 decl = lookup_member (ctype, name, 0, true, tf_warning_or_error); 318 if (!decl) 319 { 320 error ("%qT is not a member of %qT", name, ctype); 321 return; 322 } 323 if (template_member_p && !DECL_CLASS_TEMPLATE_P (decl)) 324 { 325 error ("%qT is not a member class template of %qT", 326 name, ctype); 327 error ("%q+D declared here", decl); 328 return; 329 } 330 if (!template_member_p && (TREE_CODE (decl) != TYPE_DECL 331 || !CLASS_TYPE_P (TREE_TYPE (decl)))) 332 { 333 error ("%qT is not a nested class of %qT", 334 name, ctype); 335 error ("%q+D declared here", decl); 336 return; 337 } 338 339 friend_type = CLASSTYPE_TI_TEMPLATE (TREE_TYPE (decl)); 340 } 341 } 342 } 343 else if (TREE_CODE (friend_type) == TEMPLATE_TYPE_PARM) 344 { 345 /* template <class T> friend class T; */ 346 error ("template parameter type %qT declared %<friend%>", friend_type); 347 return; 348 } 349 else if (!CLASSTYPE_TEMPLATE_INFO (friend_type)) 350 { 351 /* template <class T> friend class A; where A is not a template */ 352 error ("%q#T is not a template", friend_type); 353 return; 354 } 355 else 356 /* template <class T> friend class A; where A is a template */ 357 friend_type = CLASSTYPE_TI_TEMPLATE (friend_type); 358 359 if (friend_type == error_mark_node) 360 return; 361 362 /* See if it is already a friend. */ 363 for (classes = CLASSTYPE_FRIEND_CLASSES (type); 364 classes; 365 classes = TREE_CHAIN (classes)) 366 { 367 tree probe = TREE_VALUE (classes); 368 369 if (TREE_CODE (friend_type) == TEMPLATE_DECL) 370 { 371 if (friend_type == probe) 372 { 373 if (complain) 374 warning (0, "%qD is already a friend of %qT", probe, type); 375 break; 376 } 377 } 378 else if (TREE_CODE (probe) != TEMPLATE_DECL) 379 { 380 if (same_type_p (probe, friend_type)) 381 { 382 if (complain) 383 warning (0, "%qT is already a friend of %qT", probe, type); 384 break; 385 } 386 } 387 } 388 389 if (!classes) 390 { 391 maybe_add_class_template_decl_list (type, friend_type, /*friend_p=*/1); 392 393 CLASSTYPE_FRIEND_CLASSES (type) 394 = tree_cons (NULL_TREE, friend_type, CLASSTYPE_FRIEND_CLASSES (type)); 395 if (TREE_CODE (friend_type) == TEMPLATE_DECL) 396 friend_type = TREE_TYPE (friend_type); 397 if (!uses_template_parms (type)) 398 CLASSTYPE_BEFRIENDING_CLASSES (friend_type) 399 = tree_cons (NULL_TREE, type, 400 CLASSTYPE_BEFRIENDING_CLASSES (friend_type)); 401 } 402 } 403 404 /* Record DECL (a FUNCTION_DECL) as a friend of the 405 CURRENT_CLASS_TYPE. If DECL is a member function, CTYPE is the 406 class of which it is a member, as named in the friend declaration. 407 DECLARATOR is the name of the friend. FUNCDEF_FLAG is true if the 408 friend declaration is a definition of the function. FLAGS is as 409 for grokclass fn. */ 410 411 tree 412 do_friend (tree ctype, tree declarator, tree decl, 413 tree attrlist, enum overload_flags flags, 414 bool funcdef_flag) 415 { 416 gcc_assert (TREE_CODE (decl) == FUNCTION_DECL); 417 gcc_assert (!ctype || MAYBE_CLASS_TYPE_P (ctype)); 418 419 /* Every decl that gets here is a friend of something. */ 420 DECL_FRIEND_P (decl) = 1; 421 422 /* Unfortunately, we have to handle attributes here. Normally we would 423 handle them in start_decl_1, but since this is a friend decl start_decl_1 424 never gets to see it. */ 425 426 /* Set attributes here so if duplicate decl, will have proper attributes. */ 427 cplus_decl_attributes (&decl, attrlist, 0); 428 429 if (TREE_CODE (declarator) == TEMPLATE_ID_EXPR) 430 { 431 declarator = TREE_OPERAND (declarator, 0); 432 if (is_overloaded_fn (declarator)) 433 declarator = DECL_NAME (get_first_fn (declarator)); 434 } 435 436 if (ctype) 437 { 438 /* CLASS_TEMPLATE_DEPTH counts the number of template headers for 439 the enclosing class. FRIEND_DEPTH counts the number of template 440 headers used for this friend declaration. TEMPLATE_MEMBER_P is 441 true if a template header in FRIEND_DEPTH is intended for 442 DECLARATOR. For example, the code 443 444 template <class T> struct A { 445 template <class U> struct B { 446 template <class V> template <class W> 447 friend void C<V>::f(W); 448 }; 449 }; 450 451 will eventually give the following results 452 453 1. CLASS_TEMPLATE_DEPTH equals 2 (for `T' and `U'). 454 2. FRIEND_DEPTH equals 2 (for `V' and `W'). 455 3. TEMPLATE_MEMBER_P is true (for `W'). */ 456 457 int class_template_depth = template_class_depth (current_class_type); 458 int friend_depth = processing_template_decl - class_template_depth; 459 /* We will figure this out later. */ 460 bool template_member_p = false; 461 462 tree cname = TYPE_NAME (ctype); 463 if (TREE_CODE (cname) == TYPE_DECL) 464 cname = DECL_NAME (cname); 465 466 /* A method friend. */ 467 if (flags == NO_SPECIAL && declarator == cname) 468 DECL_CONSTRUCTOR_P (decl) = 1; 469 470 grokclassfn (ctype, decl, flags); 471 472 if (friend_depth) 473 { 474 if (!uses_template_parms_level (ctype, class_template_depth 475 + friend_depth)) 476 template_member_p = true; 477 } 478 479 /* A nested class may declare a member of an enclosing class 480 to be a friend, so we do lookup here even if CTYPE is in 481 the process of being defined. */ 482 if (class_template_depth 483 || COMPLETE_TYPE_P (ctype) 484 || (CLASS_TYPE_P (ctype) && TYPE_BEING_DEFINED (ctype))) 485 { 486 if (DECL_TEMPLATE_INFO (decl)) 487 /* DECL is a template specialization. No need to 488 build a new TEMPLATE_DECL. */ 489 ; 490 else if (class_template_depth) 491 /* We rely on tsubst_friend_function to check the 492 validity of the declaration later. */ 493 decl = push_template_decl_real (decl, /*is_friend=*/true); 494 else 495 decl = check_classfn (ctype, decl, 496 template_member_p 497 ? current_template_parms 498 : NULL_TREE); 499 500 if (template_member_p && decl && TREE_CODE (decl) == FUNCTION_DECL) 501 decl = DECL_TI_TEMPLATE (decl); 502 503 if (decl) 504 add_friend (current_class_type, decl, /*complain=*/true); 505 } 506 else 507 error ("member %qD declared as friend before type %qT defined", 508 decl, ctype); 509 } 510 /* A global friend. 511 @@ or possibly a friend from a base class ?!? */ 512 else if (TREE_CODE (decl) == FUNCTION_DECL) 513 { 514 int is_friend_template = PROCESSING_REAL_TEMPLATE_DECL_P (); 515 516 /* Friends must all go through the overload machinery, 517 even though they may not technically be overloaded. 518 519 Note that because classes all wind up being top-level 520 in their scope, their friend wind up in top-level scope as well. */ 521 if (funcdef_flag) 522 SET_DECL_FRIEND_CONTEXT (decl, current_class_type); 523 524 if (! DECL_USE_TEMPLATE (decl)) 525 { 526 /* We must check whether the decl refers to template 527 arguments before push_template_decl_real adds a 528 reference to the containing template class. */ 529 int warn = (warn_nontemplate_friend 530 && ! funcdef_flag && ! is_friend_template 531 && current_template_parms 532 && uses_template_parms (decl)); 533 534 if (is_friend_template 535 || template_class_depth (current_class_type) != 0) 536 /* We can't call pushdecl for a template class, since in 537 general, such a declaration depends on template 538 parameters. Instead, we call pushdecl when the class 539 is instantiated. */ 540 decl = push_template_decl_real (decl, /*is_friend=*/true); 541 else if (current_function_decl) 542 { 543 /* This must be a local class. 11.5p11: 544 545 If a friend declaration appears in a local class (9.8) and 546 the name specified is an unqualified name, a prior 547 declaration is looked up without considering scopes that 548 are outside the innermost enclosing non-class scope. For a 549 friend function declaration, if there is no prior 550 declaration, the program is ill-formed. */ 551 tree t = lookup_name_innermost_nonclass_level (DECL_NAME (decl)); 552 if (t) 553 decl = pushdecl_maybe_friend (decl, /*is_friend=*/true); 554 else 555 { 556 error ("friend declaration %qD in local class without " 557 "prior declaration", decl); 558 return error_mark_node; 559 } 560 } 561 else 562 { 563 /* We can't use pushdecl, as we might be in a template 564 class specialization, and pushdecl will insert an 565 unqualified friend decl into the template parameter 566 scope, rather than the namespace containing it. */ 567 tree ns = decl_namespace_context (decl); 568 569 push_nested_namespace (ns); 570 decl = pushdecl_namespace_level (decl, /*is_friend=*/true); 571 pop_nested_namespace (ns); 572 } 573 574 if (warn) 575 { 576 static int explained; 577 bool warned; 578 579 warned = warning (OPT_Wnon_template_friend, "friend declaration " 580 "%q#D declares a non-template function", decl); 581 if (! explained && warned) 582 { 583 inform (input_location, "(if this is not what you intended, make sure " 584 "the function template has already been declared " 585 "and add <> after the function name here) "); 586 explained = 1; 587 } 588 } 589 } 590 591 if (decl == error_mark_node) 592 return error_mark_node; 593 594 add_friend (current_class_type, 595 is_friend_template ? DECL_TI_TEMPLATE (decl) : decl, 596 /*complain=*/true); 597 DECL_FRIEND_P (decl) = 1; 598 } 599 600 return decl; 601 } 602