1 /*- 2 * Copyright (c) 1991, 1993 3 * The Regents of the University of California. All rights reserved. 4 * 5 * Redistribution and use in source and binary forms, with or without 6 * modification, are permitted provided that the following conditions 7 * are met: 8 * 1. Redistributions of source code must retain the above copyright 9 * notice, this list of conditions and the following disclaimer. 10 * 2. Redistributions in binary form must reproduce the above copyright 11 * notice, this list of conditions and the following disclaimer in the 12 * documentation and/or other materials provided with the distribution. 13 * 4. Neither the name of the University nor the names of its contributors 14 * may be used to endorse or promote products derived from this software 15 * without specific prior written permission. 16 * 17 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 18 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 19 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 20 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 21 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 22 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 23 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 24 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 25 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 26 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 27 * SUCH DAMAGE. 28 * 29 * @(#)queue.h 8.5 (Berkeley) 8/20/94 30 * 31 * Derived from FreeBSD src/sys/sys/queue.h:1.63. 32 * $P4: //depot/projects/trustedbsd/openbsm/compat/queue.h#3 $ 33 */ 34 35 #ifndef _COMPAT_QUEUE_H_ 36 #define _COMPAT_QUEUE_H_ 37 38 #include <sys/cdefs.h> 39 40 /* 41 * This file defines four types of data structures: singly-linked lists, 42 * singly-linked tail queues, lists and tail queues. 43 * 44 * A singly-linked list is headed by a single forward pointer. The elements 45 * are singly linked for minimum space and pointer manipulation overhead at 46 * the expense of O(n) removal for arbitrary elements. New elements can be 47 * added to the list after an existing element or at the head of the list. 48 * Elements being removed from the head of the list should use the explicit 49 * macro for this purpose for optimum efficiency. A singly-linked list may 50 * only be traversed in the forward direction. Singly-linked lists are ideal 51 * for applications with large datasets and few or no removals or for 52 * implementing a LIFO queue. 53 * 54 * A singly-linked tail queue is headed by a pair of pointers, one to the 55 * head of the list and the other to the tail of the list. The elements are 56 * singly linked for minimum space and pointer manipulation overhead at the 57 * expense of O(n) removal for arbitrary elements. New elements can be added 58 * to the list after an existing element, at the head of the list, or at the 59 * end of the list. Elements being removed from the head of the tail queue 60 * should use the explicit macro for this purpose for optimum efficiency. 61 * A singly-linked tail queue may only be traversed in the forward direction. 62 * Singly-linked tail queues are ideal for applications with large datasets 63 * and few or no removals or for implementing a FIFO queue. 64 * 65 * A list is headed by a single forward pointer (or an array of forward 66 * pointers for a hash table header). The elements are doubly linked 67 * so that an arbitrary element can be removed without a need to 68 * traverse the list. New elements can be added to the list before 69 * or after an existing element or at the head of the list. A list 70 * may only be traversed in the forward direction. 71 * 72 * A tail queue is headed by a pair of pointers, one to the head of the 73 * list and the other to the tail of the list. The elements are doubly 74 * linked so that an arbitrary element can be removed without a need to 75 * traverse the list. New elements can be added to the list before or 76 * after an existing element, at the head of the list, or at the end of 77 * the list. A tail queue may be traversed in either direction. 78 * 79 * For details on the use of these macros, see the queue(3) manual page. 80 * 81 * 82 * SLIST LIST STAILQ TAILQ 83 * _HEAD + + + + 84 * _HEAD_INITIALIZER + + + + 85 * _ENTRY + + + + 86 * _INIT + + + + 87 * _EMPTY + + + + 88 * _FIRST + + + + 89 * _NEXT + + + + 90 * _PREV - - - + 91 * _LAST - - + + 92 * _FOREACH + + + + 93 * _FOREACH_SAFE + + + + 94 * _FOREACH_REVERSE - - - + 95 * _FOREACH_REVERSE_SAFE - - - + 96 * _INSERT_HEAD + + + + 97 * _INSERT_BEFORE - + - + 98 * _INSERT_AFTER + + + + 99 * _INSERT_TAIL - - + + 100 * _CONCAT - - + + 101 * _REMOVE_HEAD + - + - 102 * _REMOVE + + + + 103 * 104 */ 105 #ifdef QUEUE_MACRO_DEBUG 106 /* Store the last 2 places the queue element or head was altered */ 107 struct qm_trace { 108 char * lastfile; 109 int lastline; 110 char * prevfile; 111 int prevline; 112 }; 113 114 #define TRACEBUF struct qm_trace trace; 115 #define TRASHIT(x) do {(x) = (void *)-1;} while (0) 116 117 #define QMD_TRACE_HEAD(head) do { \ 118 (head)->trace.prevline = (head)->trace.lastline; \ 119 (head)->trace.prevfile = (head)->trace.lastfile; \ 120 (head)->trace.lastline = __LINE__; \ 121 (head)->trace.lastfile = __FILE__; \ 122 } while (0) 123 124 #define QMD_TRACE_ELEM(elem) do { \ 125 (elem)->trace.prevline = (elem)->trace.lastline; \ 126 (elem)->trace.prevfile = (elem)->trace.lastfile; \ 127 (elem)->trace.lastline = __LINE__; \ 128 (elem)->trace.lastfile = __FILE__; \ 129 } while (0) 130 131 #else 132 #define QMD_TRACE_ELEM(elem) 133 #define QMD_TRACE_HEAD(head) 134 #define TRACEBUF 135 #define TRASHIT(x) 136 #endif /* QUEUE_MACRO_DEBUG */ 137 138 /* 139 * Singly-linked List declarations. 140 */ 141 #define SLIST_HEAD(name, type) \ 142 struct name { \ 143 struct type *slh_first; /* first element */ \ 144 } 145 146 #define SLIST_HEAD_INITIALIZER(head) \ 147 { NULL } 148 149 #define SLIST_ENTRY(type) \ 150 struct { \ 151 struct type *sle_next; /* next element */ \ 152 } 153 154 /* 155 * Singly-linked List functions. 156 */ 157 #define SLIST_EMPTY(head) ((head)->slh_first == NULL) 158 159 #define SLIST_FIRST(head) ((head)->slh_first) 160 161 #define SLIST_FOREACH(var, head, field) \ 162 for ((var) = SLIST_FIRST((head)); \ 163 (var); \ 164 (var) = SLIST_NEXT((var), field)) 165 166 #define SLIST_FOREACH_SAFE(var, head, field, tvar) \ 167 for ((var) = SLIST_FIRST((head)); \ 168 (var) && ((tvar) = SLIST_NEXT((var), field), 1); \ 169 (var) = (tvar)) 170 171 #define SLIST_FOREACH_PREVPTR(var, varp, head, field) \ 172 for ((varp) = &SLIST_FIRST((head)); \ 173 ((var) = *(varp)) != NULL; \ 174 (varp) = &SLIST_NEXT((var), field)) 175 176 #define SLIST_INIT(head) do { \ 177 SLIST_FIRST((head)) = NULL; \ 178 } while (0) 179 180 #define SLIST_INSERT_AFTER(slistelm, elm, field) do { \ 181 SLIST_NEXT((elm), field) = SLIST_NEXT((slistelm), field); \ 182 SLIST_NEXT((slistelm), field) = (elm); \ 183 } while (0) 184 185 #define SLIST_INSERT_HEAD(head, elm, field) do { \ 186 SLIST_NEXT((elm), field) = SLIST_FIRST((head)); \ 187 SLIST_FIRST((head)) = (elm); \ 188 } while (0) 189 190 #define SLIST_NEXT(elm, field) ((elm)->field.sle_next) 191 192 #define SLIST_REMOVE(head, elm, type, field) do { \ 193 if (SLIST_FIRST((head)) == (elm)) { \ 194 SLIST_REMOVE_HEAD((head), field); \ 195 } \ 196 else { \ 197 struct type *curelm = SLIST_FIRST((head)); \ 198 while (SLIST_NEXT(curelm, field) != (elm)) \ 199 curelm = SLIST_NEXT(curelm, field); \ 200 SLIST_NEXT(curelm, field) = \ 201 SLIST_NEXT(SLIST_NEXT(curelm, field), field); \ 202 } \ 203 TRASHIT((elm)->field.sle_next); \ 204 } while (0) 205 206 #define SLIST_REMOVE_HEAD(head, field) do { \ 207 SLIST_FIRST((head)) = SLIST_NEXT(SLIST_FIRST((head)), field); \ 208 } while (0) 209 210 /* 211 * Singly-linked Tail queue declarations. 212 */ 213 #define STAILQ_HEAD(name, type) \ 214 struct name { \ 215 struct type *stqh_first;/* first element */ \ 216 struct type **stqh_last;/* addr of last next element */ \ 217 } 218 219 #define STAILQ_HEAD_INITIALIZER(head) \ 220 { NULL, &(head).stqh_first } 221 222 #define STAILQ_ENTRY(type) \ 223 struct { \ 224 struct type *stqe_next; /* next element */ \ 225 } 226 227 /* 228 * Singly-linked Tail queue functions. 229 */ 230 #define STAILQ_CONCAT(head1, head2) do { \ 231 if (!STAILQ_EMPTY((head2))) { \ 232 *(head1)->stqh_last = (head2)->stqh_first; \ 233 (head1)->stqh_last = (head2)->stqh_last; \ 234 STAILQ_INIT((head2)); \ 235 } \ 236 } while (0) 237 238 #define STAILQ_EMPTY(head) ((head)->stqh_first == NULL) 239 240 #define STAILQ_FIRST(head) ((head)->stqh_first) 241 242 #define STAILQ_FOREACH(var, head, field) \ 243 for((var) = STAILQ_FIRST((head)); \ 244 (var); \ 245 (var) = STAILQ_NEXT((var), field)) 246 247 248 #define STAILQ_FOREACH_SAFE(var, head, field, tvar) \ 249 for ((var) = STAILQ_FIRST((head)); \ 250 (var) && ((tvar) = STAILQ_NEXT((var), field), 1); \ 251 (var) = (tvar)) 252 253 #define STAILQ_INIT(head) do { \ 254 STAILQ_FIRST((head)) = NULL; \ 255 (head)->stqh_last = &STAILQ_FIRST((head)); \ 256 } while (0) 257 258 #define STAILQ_INSERT_AFTER(head, tqelm, elm, field) do { \ 259 if ((STAILQ_NEXT((elm), field) = STAILQ_NEXT((tqelm), field)) == NULL)\ 260 (head)->stqh_last = &STAILQ_NEXT((elm), field); \ 261 STAILQ_NEXT((tqelm), field) = (elm); \ 262 } while (0) 263 264 #define STAILQ_INSERT_HEAD(head, elm, field) do { \ 265 if ((STAILQ_NEXT((elm), field) = STAILQ_FIRST((head))) == NULL) \ 266 (head)->stqh_last = &STAILQ_NEXT((elm), field); \ 267 STAILQ_FIRST((head)) = (elm); \ 268 } while (0) 269 270 #define STAILQ_INSERT_TAIL(head, elm, field) do { \ 271 STAILQ_NEXT((elm), field) = NULL; \ 272 *(head)->stqh_last = (elm); \ 273 (head)->stqh_last = &STAILQ_NEXT((elm), field); \ 274 } while (0) 275 276 #define STAILQ_LAST(head, type, field) \ 277 (STAILQ_EMPTY((head)) ? \ 278 NULL : \ 279 ((struct type *) \ 280 ((char *)((head)->stqh_last) - __offsetof(struct type, field)))) 281 282 #define STAILQ_NEXT(elm, field) ((elm)->field.stqe_next) 283 284 #define STAILQ_REMOVE(head, elm, type, field) do { \ 285 if (STAILQ_FIRST((head)) == (elm)) { \ 286 STAILQ_REMOVE_HEAD((head), field); \ 287 } \ 288 else { \ 289 struct type *curelm = STAILQ_FIRST((head)); \ 290 while (STAILQ_NEXT(curelm, field) != (elm)) \ 291 curelm = STAILQ_NEXT(curelm, field); \ 292 if ((STAILQ_NEXT(curelm, field) = \ 293 STAILQ_NEXT(STAILQ_NEXT(curelm, field), field)) == NULL)\ 294 (head)->stqh_last = &STAILQ_NEXT((curelm), field);\ 295 } \ 296 TRASHIT((elm)->field.stqe_next); \ 297 } while (0) 298 299 #define STAILQ_REMOVE_HEAD(head, field) do { \ 300 if ((STAILQ_FIRST((head)) = \ 301 STAILQ_NEXT(STAILQ_FIRST((head)), field)) == NULL) \ 302 (head)->stqh_last = &STAILQ_FIRST((head)); \ 303 } while (0) 304 305 #define STAILQ_REMOVE_HEAD_UNTIL(head, elm, field) do { \ 306 if ((STAILQ_FIRST((head)) = STAILQ_NEXT((elm), field)) == NULL) \ 307 (head)->stqh_last = &STAILQ_FIRST((head)); \ 308 } while (0) 309 310 /* 311 * List declarations. 312 */ 313 #define LIST_HEAD(name, type) \ 314 struct name { \ 315 struct type *lh_first; /* first element */ \ 316 } 317 318 #define LIST_HEAD_INITIALIZER(head) \ 319 { NULL } 320 321 #define LIST_ENTRY(type) \ 322 struct { \ 323 struct type *le_next; /* next element */ \ 324 struct type **le_prev; /* address of previous next element */ \ 325 } 326 327 /* 328 * List functions. 329 */ 330 331 #if (defined(_KERNEL) && defined(INVARIANTS)) || defined(QUEUE_MACRO_DEBUG) 332 #define QMD_LIST_CHECK_HEAD(head, field) do { \ 333 if (LIST_FIRST((head)) != NULL && \ 334 LIST_FIRST((head))->field.le_prev != \ 335 &LIST_FIRST((head))) \ 336 panic("Bad list head %p first->prev != head", (head)); \ 337 } while (0) 338 339 #define QMD_LIST_CHECK_NEXT(elm, field) do { \ 340 if (LIST_NEXT((elm), field) != NULL && \ 341 LIST_NEXT((elm), field)->field.le_prev != \ 342 &((elm)->field.le_next)) \ 343 panic("Bad link elm %p next->prev != elm", (elm)); \ 344 } while (0) 345 346 #define QMD_LIST_CHECK_PREV(elm, field) do { \ 347 if (*(elm)->field.le_prev != (elm)) \ 348 panic("Bad link elm %p prev->next != elm", (elm)); \ 349 } while (0) 350 #else 351 #define QMD_LIST_CHECK_HEAD(head, field) 352 #define QMD_LIST_CHECK_NEXT(elm, field) 353 #define QMD_LIST_CHECK_PREV(elm, field) 354 #endif /* (_KERNEL && INVARIANTS) || QUEUE_MACRO_DEBUG */ 355 356 #define LIST_EMPTY(head) ((head)->lh_first == NULL) 357 358 #define LIST_FIRST(head) ((head)->lh_first) 359 360 #define LIST_FOREACH(var, head, field) \ 361 for ((var) = LIST_FIRST((head)); \ 362 (var); \ 363 (var) = LIST_NEXT((var), field)) 364 365 #define LIST_FOREACH_SAFE(var, head, field, tvar) \ 366 for ((var) = LIST_FIRST((head)); \ 367 (var) && ((tvar) = LIST_NEXT((var), field), 1); \ 368 (var) = (tvar)) 369 370 #define LIST_INIT(head) do { \ 371 LIST_FIRST((head)) = NULL; \ 372 } while (0) 373 374 #define LIST_INSERT_AFTER(listelm, elm, field) do { \ 375 QMD_LIST_CHECK_NEXT(listelm, field); \ 376 if ((LIST_NEXT((elm), field) = LIST_NEXT((listelm), field)) != NULL)\ 377 LIST_NEXT((listelm), field)->field.le_prev = \ 378 &LIST_NEXT((elm), field); \ 379 LIST_NEXT((listelm), field) = (elm); \ 380 (elm)->field.le_prev = &LIST_NEXT((listelm), field); \ 381 } while (0) 382 383 #define LIST_INSERT_BEFORE(listelm, elm, field) do { \ 384 QMD_LIST_CHECK_PREV(listelm, field); \ 385 (elm)->field.le_prev = (listelm)->field.le_prev; \ 386 LIST_NEXT((elm), field) = (listelm); \ 387 *(listelm)->field.le_prev = (elm); \ 388 (listelm)->field.le_prev = &LIST_NEXT((elm), field); \ 389 } while (0) 390 391 #define LIST_INSERT_HEAD(head, elm, field) do { \ 392 QMD_LIST_CHECK_HEAD((head), field); \ 393 if ((LIST_NEXT((elm), field) = LIST_FIRST((head))) != NULL) \ 394 LIST_FIRST((head))->field.le_prev = &LIST_NEXT((elm), field);\ 395 LIST_FIRST((head)) = (elm); \ 396 (elm)->field.le_prev = &LIST_FIRST((head)); \ 397 } while (0) 398 399 #define LIST_NEXT(elm, field) ((elm)->field.le_next) 400 401 #define LIST_REMOVE(elm, field) do { \ 402 QMD_LIST_CHECK_NEXT(elm, field); \ 403 QMD_LIST_CHECK_PREV(elm, field); \ 404 if (LIST_NEXT((elm), field) != NULL) \ 405 LIST_NEXT((elm), field)->field.le_prev = \ 406 (elm)->field.le_prev; \ 407 *(elm)->field.le_prev = LIST_NEXT((elm), field); \ 408 TRASHIT((elm)->field.le_next); \ 409 TRASHIT((elm)->field.le_prev); \ 410 } while (0) 411 412 /* 413 * Tail queue declarations. 414 */ 415 #define TAILQ_HEAD(name, type) \ 416 struct name { \ 417 struct type *tqh_first; /* first element */ \ 418 struct type **tqh_last; /* addr of last next element */ \ 419 TRACEBUF \ 420 } 421 422 #define TAILQ_HEAD_INITIALIZER(head) \ 423 { NULL, &(head).tqh_first } 424 425 #define TAILQ_ENTRY(type) \ 426 struct { \ 427 struct type *tqe_next; /* next element */ \ 428 struct type **tqe_prev; /* address of previous next element */ \ 429 TRACEBUF \ 430 } 431 432 /* 433 * Tail queue functions. 434 */ 435 #define TAILQ_CONCAT(head1, head2, field) do { \ 436 if (!TAILQ_EMPTY(head2)) { \ 437 *(head1)->tqh_last = (head2)->tqh_first; \ 438 (head2)->tqh_first->field.tqe_prev = (head1)->tqh_last; \ 439 (head1)->tqh_last = (head2)->tqh_last; \ 440 TAILQ_INIT((head2)); \ 441 QMD_TRACE_HEAD(head1); \ 442 QMD_TRACE_HEAD(head2); \ 443 } \ 444 } while (0) 445 446 #define TAILQ_EMPTY(head) ((head)->tqh_first == NULL) 447 448 #define TAILQ_FIRST(head) ((head)->tqh_first) 449 450 #define TAILQ_FOREACH(var, head, field) \ 451 for ((var) = TAILQ_FIRST((head)); \ 452 (var); \ 453 (var) = TAILQ_NEXT((var), field)) 454 455 #define TAILQ_FOREACH_SAFE(var, head, field, tvar) \ 456 for ((var) = TAILQ_FIRST((head)); \ 457 (var) && ((tvar) = TAILQ_NEXT((var), field), 1); \ 458 (var) = (tvar)) 459 460 #define TAILQ_FOREACH_REVERSE(var, head, headname, field) \ 461 for ((var) = TAILQ_LAST((head), headname); \ 462 (var); \ 463 (var) = TAILQ_PREV((var), headname, field)) 464 465 #define TAILQ_FOREACH_REVERSE_SAFE(var, head, headname, field, tvar) \ 466 for ((var) = TAILQ_LAST((head), headname); \ 467 (var) && ((tvar) = TAILQ_PREV((var), headname, field), 1); \ 468 (var) = (tvar)) 469 470 #define TAILQ_INIT(head) do { \ 471 TAILQ_FIRST((head)) = NULL; \ 472 (head)->tqh_last = &TAILQ_FIRST((head)); \ 473 QMD_TRACE_HEAD(head); \ 474 } while (0) 475 476 #define TAILQ_INSERT_AFTER(head, listelm, elm, field) do { \ 477 if ((TAILQ_NEXT((elm), field) = TAILQ_NEXT((listelm), field)) != NULL)\ 478 TAILQ_NEXT((elm), field)->field.tqe_prev = \ 479 &TAILQ_NEXT((elm), field); \ 480 else { \ 481 (head)->tqh_last = &TAILQ_NEXT((elm), field); \ 482 QMD_TRACE_HEAD(head); \ 483 } \ 484 TAILQ_NEXT((listelm), field) = (elm); \ 485 (elm)->field.tqe_prev = &TAILQ_NEXT((listelm), field); \ 486 QMD_TRACE_ELEM(&(elm)->field); \ 487 QMD_TRACE_ELEM(&listelm->field); \ 488 } while (0) 489 490 #define TAILQ_INSERT_BEFORE(listelm, elm, field) do { \ 491 (elm)->field.tqe_prev = (listelm)->field.tqe_prev; \ 492 TAILQ_NEXT((elm), field) = (listelm); \ 493 *(listelm)->field.tqe_prev = (elm); \ 494 (listelm)->field.tqe_prev = &TAILQ_NEXT((elm), field); \ 495 QMD_TRACE_ELEM(&(elm)->field); \ 496 QMD_TRACE_ELEM(&listelm->field); \ 497 } while (0) 498 499 #define TAILQ_INSERT_HEAD(head, elm, field) do { \ 500 if ((TAILQ_NEXT((elm), field) = TAILQ_FIRST((head))) != NULL) \ 501 TAILQ_FIRST((head))->field.tqe_prev = \ 502 &TAILQ_NEXT((elm), field); \ 503 else \ 504 (head)->tqh_last = &TAILQ_NEXT((elm), field); \ 505 TAILQ_FIRST((head)) = (elm); \ 506 (elm)->field.tqe_prev = &TAILQ_FIRST((head)); \ 507 QMD_TRACE_HEAD(head); \ 508 QMD_TRACE_ELEM(&(elm)->field); \ 509 } while (0) 510 511 #define TAILQ_INSERT_TAIL(head, elm, field) do { \ 512 TAILQ_NEXT((elm), field) = NULL; \ 513 (elm)->field.tqe_prev = (head)->tqh_last; \ 514 *(head)->tqh_last = (elm); \ 515 (head)->tqh_last = &TAILQ_NEXT((elm), field); \ 516 QMD_TRACE_HEAD(head); \ 517 QMD_TRACE_ELEM(&(elm)->field); \ 518 } while (0) 519 520 #define TAILQ_LAST(head, headname) \ 521 (*(((struct headname *)((head)->tqh_last))->tqh_last)) 522 523 #define TAILQ_NEXT(elm, field) ((elm)->field.tqe_next) 524 525 #define TAILQ_PREV(elm, headname, field) \ 526 (*(((struct headname *)((elm)->field.tqe_prev))->tqh_last)) 527 528 #define TAILQ_REMOVE(head, elm, field) do { \ 529 if ((TAILQ_NEXT((elm), field)) != NULL) \ 530 TAILQ_NEXT((elm), field)->field.tqe_prev = \ 531 (elm)->field.tqe_prev; \ 532 else { \ 533 (head)->tqh_last = (elm)->field.tqe_prev; \ 534 QMD_TRACE_HEAD(head); \ 535 } \ 536 *(elm)->field.tqe_prev = TAILQ_NEXT((elm), field); \ 537 TRASHIT((elm)->field.tqe_next); \ 538 TRASHIT((elm)->field.tqe_prev); \ 539 QMD_TRACE_ELEM(&(elm)->field); \ 540 } while (0) 541 542 #endif /* !_COMPAT_QUEUE_H_ */ 543