xref: /openbsd-src/usr.bin/mandoc/mansearch.c (revision c90a81c56dcebd6a1b73fe4aff9b03385b8e63b3)
1 /*	$OpenBSD: mansearch.c,v 1.63 2018/12/13 11:55:14 schwarze Exp $ */
2 /*
3  * Copyright (c) 2012 Kristaps Dzonsons <kristaps@bsd.lv>
4  * Copyright (c) 2013-2018 Ingo Schwarze <schwarze@openbsd.org>
5  *
6  * Permission to use, copy, modify, and distribute this software for any
7  * purpose with or without fee is hereby granted, provided that the above
8  * copyright notice and this permission notice appear in all copies.
9  *
10  * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHORS DISCLAIM ALL WARRANTIES
11  * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
12  * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR
13  * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
14  * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
15  * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
16  * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
17  */
18 
19 #include <sys/mman.h>
20 #include <sys/types.h>
21 
22 #include <assert.h>
23 #include <err.h>
24 #include <errno.h>
25 #include <fcntl.h>
26 #include <glob.h>
27 #include <limits.h>
28 #include <regex.h>
29 #include <stdio.h>
30 #include <stdint.h>
31 #include <stddef.h>
32 #include <stdlib.h>
33 #include <string.h>
34 #include <unistd.h>
35 
36 #include "mandoc_aux.h"
37 #include "mandoc_ohash.h"
38 #include "manconf.h"
39 #include "mansearch.h"
40 #include "dbm.h"
41 
42 struct	expr {
43 	/* Used for terms: */
44 	struct dbm_match match;   /* Match type and expression. */
45 	uint64_t	 bits;    /* Type mask. */
46 	/* Used for OR and AND groups: */
47 	struct expr	*next;    /* Next child in the parent group. */
48 	struct expr	*child;   /* First child in this group. */
49 	enum { EXPR_TERM, EXPR_OR, EXPR_AND } type;
50 };
51 
52 const char *const mansearch_keynames[KEY_MAX] = {
53 	"arch",	"sec",	"Xr",	"Ar",	"Fa",	"Fl",	"Dv",	"Fn",
54 	"Ic",	"Pa",	"Cm",	"Li",	"Em",	"Cd",	"Va",	"Ft",
55 	"Tn",	"Er",	"Ev",	"Sy",	"Sh",	"In",	"Ss",	"Ox",
56 	"An",	"Mt",	"St",	"Bx",	"At",	"Nx",	"Fx",	"Lk",
57 	"Ms",	"Bsx",	"Dx",	"Rs",	"Vt",	"Lb",	"Nm",	"Nd"
58 };
59 
60 
61 static	struct ohash	*manmerge(struct expr *, struct ohash *);
62 static	struct ohash	*manmerge_term(struct expr *, struct ohash *);
63 static	struct ohash	*manmerge_or(struct expr *, struct ohash *);
64 static	struct ohash	*manmerge_and(struct expr *, struct ohash *);
65 static	char		*buildnames(const struct dbm_page *);
66 static	char		*buildoutput(size_t, struct dbm_page *);
67 static	size_t		 lstlen(const char *, size_t);
68 static	void		 lstcat(char *, size_t *, const char *, const char *);
69 static	int		 lstmatch(const char *, const char *);
70 static	struct expr	*exprcomp(const struct mansearch *,
71 				int, char *[], int *);
72 static	struct expr	*expr_and(const struct mansearch *,
73 				int, char *[], int *);
74 static	struct expr	*exprterm(const struct mansearch *,
75 				int, char *[], int *);
76 static	void		 exprfree(struct expr *);
77 static	int		 manpage_compare(const void *, const void *);
78 
79 
80 int
81 mansearch(const struct mansearch *search,
82 		const struct manpaths *paths,
83 		int argc, char *argv[],
84 		struct manpage **res, size_t *sz)
85 {
86 	char		 buf[PATH_MAX];
87 	struct dbm_res	*rp;
88 	struct expr	*e;
89 	struct dbm_page	*page;
90 	struct manpage	*mpage;
91 	struct ohash	*htab;
92 	size_t		 cur, i, maxres, outkey;
93 	unsigned int	 slot;
94 	int		 argi, chdir_status, getcwd_status, im;
95 
96 	argi = 0;
97 	if ((e = exprcomp(search, argc, argv, &argi)) == NULL) {
98 		*sz = 0;
99 		return 0;
100 	}
101 
102 	cur = maxres = 0;
103 	if (res != NULL)
104 		*res = NULL;
105 
106 	outkey = KEY_Nd;
107 	if (search->outkey != NULL)
108 		for (im = 0; im < KEY_MAX; im++)
109 			if (0 == strcasecmp(search->outkey,
110 			    mansearch_keynames[im])) {
111 				outkey = im;
112 				break;
113 			}
114 
115 	/*
116 	 * Remember the original working directory, if possible.
117 	 * This will be needed if the second or a later directory
118 	 * is given as a relative path.
119 	 * Do not error out if the current directory is not
120 	 * searchable: Maybe it won't be needed after all.
121 	 */
122 
123 	if (getcwd(buf, PATH_MAX) == NULL) {
124 		getcwd_status = 0;
125 		(void)strlcpy(buf, strerror(errno), sizeof(buf));
126 	} else
127 		getcwd_status = 1;
128 
129 	/*
130 	 * Loop over the directories (containing databases) for us to
131 	 * search.
132 	 * Don't let missing/bad databases/directories phase us.
133 	 * In each, try to open the resident database and, if it opens,
134 	 * scan it for our match expression.
135 	 */
136 
137 	chdir_status = 0;
138 	for (i = 0; i < paths->sz; i++) {
139 		if (chdir_status && paths->paths[i][0] != '/') {
140 			if ( ! getcwd_status) {
141 				warnx("%s: getcwd: %s", paths->paths[i], buf);
142 				continue;
143 			} else if (chdir(buf) == -1) {
144 				warn("%s", buf);
145 				continue;
146 			}
147 		}
148 		if (chdir(paths->paths[i]) == -1) {
149 			warn("%s", paths->paths[i]);
150 			continue;
151 		}
152 		chdir_status = 1;
153 
154 		if (dbm_open(MANDOC_DB) == -1) {
155 			if (errno != ENOENT)
156 				warn("%s/%s", paths->paths[i], MANDOC_DB);
157 			continue;
158 		}
159 
160 		if ((htab = manmerge(e, NULL)) == NULL) {
161 			dbm_close();
162 			continue;
163 		}
164 
165 		for (rp = ohash_first(htab, &slot); rp != NULL;
166 		    rp = ohash_next(htab, &slot)) {
167 			page = dbm_page_get(rp->page);
168 
169 			if (lstmatch(search->sec, page->sect) == 0 ||
170 			    lstmatch(search->arch, page->arch) == 0 ||
171 			    (search->argmode == ARG_NAME &&
172 			     rp->bits <= (int32_t)(NAME_SYN & NAME_MASK)))
173 				continue;
174 
175 			if (res == NULL) {
176 				cur = 1;
177 				break;
178 			}
179 			if (cur + 1 > maxres) {
180 				maxres += 1024;
181 				*res = mandoc_reallocarray(*res,
182 				    maxres, sizeof(**res));
183 			}
184 			mpage = *res + cur;
185 			mandoc_asprintf(&mpage->file, "%s/%s",
186 			    paths->paths[i], page->file + 1);
187 			if (access(chdir_status ? page->file + 1 :
188 			    mpage->file, R_OK) == -1) {
189 				warn("%s", mpage->file);
190 				warnx("outdated mandoc.db contains "
191 				    "bogus %s entry, run makewhatis %s",
192 				    page->file + 1, paths->paths[i]);
193 				free(mpage->file);
194 				free(rp);
195 				continue;
196 			}
197 			mpage->names = buildnames(page);
198 			mpage->output = buildoutput(outkey, page);
199 			mpage->ipath = i;
200 			mpage->sec = *page->sect - '0';
201 			if (mpage->sec < 0 || mpage->sec > 9)
202 				mpage->sec = 10;
203 			mpage->form = *page->file;
204 			free(rp);
205 			cur++;
206 		}
207 		ohash_delete(htab);
208 		free(htab);
209 		dbm_close();
210 
211 		/*
212 		 * In man(1) mode, prefer matches in earlier trees
213 		 * over matches in later trees.
214 		 */
215 
216 		if (cur && search->firstmatch)
217 			break;
218 	}
219 	if (res != NULL)
220 		qsort(*res, cur, sizeof(struct manpage), manpage_compare);
221 	if (chdir_status && getcwd_status && chdir(buf) == -1)
222 		warn("%s", buf);
223 	exprfree(e);
224 	*sz = cur;
225 	return res != NULL || cur;
226 }
227 
228 /*
229  * Merge the results for the expression tree rooted at e
230  * into the the result list htab.
231  */
232 static struct ohash *
233 manmerge(struct expr *e, struct ohash *htab)
234 {
235 	switch (e->type) {
236 	case EXPR_TERM:
237 		return manmerge_term(e, htab);
238 	case EXPR_OR:
239 		return manmerge_or(e->child, htab);
240 	case EXPR_AND:
241 		return manmerge_and(e->child, htab);
242 	default:
243 		abort();
244 	}
245 }
246 
247 static struct ohash *
248 manmerge_term(struct expr *e, struct ohash *htab)
249 {
250 	struct dbm_res	 res, *rp;
251 	uint64_t	 ib;
252 	unsigned int	 slot;
253 	int		 im;
254 
255 	if (htab == NULL) {
256 		htab = mandoc_malloc(sizeof(*htab));
257 		mandoc_ohash_init(htab, 4, offsetof(struct dbm_res, page));
258 	}
259 
260 	for (im = 0, ib = 1; im < KEY_MAX; im++, ib <<= 1) {
261 		if ((e->bits & ib) == 0)
262 			continue;
263 
264 		switch (ib) {
265 		case TYPE_arch:
266 			dbm_page_byarch(&e->match);
267 			break;
268 		case TYPE_sec:
269 			dbm_page_bysect(&e->match);
270 			break;
271 		case TYPE_Nm:
272 			dbm_page_byname(&e->match);
273 			break;
274 		case TYPE_Nd:
275 			dbm_page_bydesc(&e->match);
276 			break;
277 		default:
278 			dbm_page_bymacro(im - 2, &e->match);
279 			break;
280 		}
281 
282 		/*
283 		 * When hashing for deduplication, use the unique
284 		 * page ID itself instead of a hash function;
285 		 * that is quite efficient.
286 		 */
287 
288 		for (;;) {
289 			res = dbm_page_next();
290 			if (res.page == -1)
291 				break;
292 			slot = ohash_lookup_memory(htab,
293 			    (char *)&res, sizeof(res.page), res.page);
294 			if ((rp = ohash_find(htab, slot)) != NULL)
295 				continue;
296 			rp = mandoc_malloc(sizeof(*rp));
297 			*rp = res;
298 			ohash_insert(htab, slot, rp);
299 		}
300 	}
301 	return htab;
302 }
303 
304 static struct ohash *
305 manmerge_or(struct expr *e, struct ohash *htab)
306 {
307 	while (e != NULL) {
308 		htab = manmerge(e, htab);
309 		e = e->next;
310 	}
311 	return htab;
312 }
313 
314 static struct ohash *
315 manmerge_and(struct expr *e, struct ohash *htab)
316 {
317 	struct ohash	*hand, *h1, *h2;
318 	struct dbm_res	*res;
319 	unsigned int	 slot1, slot2;
320 
321 	/* Evaluate the first term of the AND clause. */
322 
323 	hand = manmerge(e, NULL);
324 
325 	while ((e = e->next) != NULL) {
326 
327 		/* Evaluate the next term and prepare for ANDing. */
328 
329 		h2 = manmerge(e, NULL);
330 		if (ohash_entries(h2) < ohash_entries(hand)) {
331 			h1 = h2;
332 			h2 = hand;
333 		} else
334 			h1 = hand;
335 		hand = mandoc_malloc(sizeof(*hand));
336 		mandoc_ohash_init(hand, 4, offsetof(struct dbm_res, page));
337 
338 		/* Keep all pages that are in both result sets. */
339 
340 		for (res = ohash_first(h1, &slot1); res != NULL;
341 		    res = ohash_next(h1, &slot1)) {
342 			if (ohash_find(h2, ohash_lookup_memory(h2,
343 			    (char *)res, sizeof(res->page),
344 			    res->page)) == NULL)
345 				free(res);
346 			else
347 				ohash_insert(hand, ohash_lookup_memory(hand,
348 				    (char *)res, sizeof(res->page),
349 				    res->page), res);
350 		}
351 
352 		/* Discard the merged results. */
353 
354 		for (res = ohash_first(h2, &slot2); res != NULL;
355 		    res = ohash_next(h2, &slot2))
356 			free(res);
357 		ohash_delete(h2);
358 		free(h2);
359 		ohash_delete(h1);
360 		free(h1);
361 	}
362 
363 	/* Merge the result of the AND into htab. */
364 
365 	if (htab == NULL)
366 		return hand;
367 
368 	for (res = ohash_first(hand, &slot1); res != NULL;
369 	    res = ohash_next(hand, &slot1)) {
370 		slot2 = ohash_lookup_memory(htab,
371 		    (char *)res, sizeof(res->page), res->page);
372 		if (ohash_find(htab, slot2) == NULL)
373 			ohash_insert(htab, slot2, res);
374 		else
375 			free(res);
376 	}
377 
378 	/* Discard the merged result. */
379 
380 	ohash_delete(hand);
381 	free(hand);
382 	return htab;
383 }
384 
385 void
386 mansearch_free(struct manpage *res, size_t sz)
387 {
388 	size_t	 i;
389 
390 	for (i = 0; i < sz; i++) {
391 		free(res[i].file);
392 		free(res[i].names);
393 		free(res[i].output);
394 	}
395 	free(res);
396 }
397 
398 static int
399 manpage_compare(const void *vp1, const void *vp2)
400 {
401 	const struct manpage	*mp1, *mp2;
402 	const char		*cp1, *cp2;
403 	size_t			 sz1, sz2;
404 	int			 diff;
405 
406 	mp1 = vp1;
407 	mp2 = vp2;
408 	if ((diff = mp1->sec - mp2->sec))
409 		return diff;
410 
411 	/* Fall back to alphabetic ordering of names. */
412 	sz1 = strcspn(mp1->names, "(");
413 	sz2 = strcspn(mp2->names, "(");
414 	if (sz1 < sz2)
415 		sz1 = sz2;
416 	if ((diff = strncasecmp(mp1->names, mp2->names, sz1)))
417 		return diff;
418 
419 	/* For identical names and sections, prefer arch-dependent. */
420 	cp1 = strchr(mp1->names + sz1, '/');
421 	cp2 = strchr(mp2->names + sz2, '/');
422 	return cp1 != NULL && cp2 != NULL ? strcasecmp(cp1, cp2) :
423 	    cp1 != NULL ? -1 : cp2 != NULL ? 1 : 0;
424 }
425 
426 static char *
427 buildnames(const struct dbm_page *page)
428 {
429 	char	*buf;
430 	size_t	 i, sz;
431 
432 	sz = lstlen(page->name, 2) + 1 + lstlen(page->sect, 2) +
433 	    (page->arch == NULL ? 0 : 1 + lstlen(page->arch, 2)) + 2;
434 	buf = mandoc_malloc(sz);
435 	i = 0;
436 	lstcat(buf, &i, page->name, ", ");
437 	buf[i++] = '(';
438 	lstcat(buf, &i, page->sect, ", ");
439 	if (page->arch != NULL) {
440 		buf[i++] = '/';
441 		lstcat(buf, &i, page->arch, ", ");
442 	}
443 	buf[i++] = ')';
444 	buf[i++] = '\0';
445 	assert(i == sz);
446 	return buf;
447 }
448 
449 /*
450  * Count the buffer space needed to print the NUL-terminated
451  * list of NUL-terminated strings, when printing sep separator
452  * characters between strings.
453  */
454 static size_t
455 lstlen(const char *cp, size_t sep)
456 {
457 	size_t	 sz;
458 
459 	for (sz = 0; *cp != '\0'; cp++) {
460 
461 		/* Skip names appearing only in the SYNOPSIS. */
462 		if (*cp <= (char)(NAME_SYN & NAME_MASK)) {
463 			while (*cp != '\0')
464 				cp++;
465 			continue;
466 		}
467 
468 		/* Skip name class markers. */
469 		if (*cp < ' ')
470 			cp++;
471 
472 		/* Print a separator before each but the first string. */
473 		if (sz)
474 			sz += sep;
475 
476 		/* Copy one string. */
477 		while (*cp != '\0') {
478 			sz++;
479 			cp++;
480 		}
481 	}
482 	return sz;
483 }
484 
485 /*
486  * Print the NUL-terminated list of NUL-terminated strings
487  * into the buffer, seperating strings with sep.
488  */
489 static void
490 lstcat(char *buf, size_t *i, const char *cp, const char *sep)
491 {
492 	const char	*s;
493 	size_t		 i_start;
494 
495 	for (i_start = *i; *cp != '\0'; cp++) {
496 
497 		/* Skip names appearing only in the SYNOPSIS. */
498 		if (*cp <= (char)(NAME_SYN & NAME_MASK)) {
499 			while (*cp != '\0')
500 				cp++;
501 			continue;
502 		}
503 
504 		/* Skip name class markers. */
505 		if (*cp < ' ')
506 			cp++;
507 
508 		/* Print a separator before each but the first string. */
509 		if (*i > i_start) {
510 			s = sep;
511 			while (*s != '\0')
512 				buf[(*i)++] = *s++;
513 		}
514 
515 		/* Copy one string. */
516 		while (*cp != '\0')
517 			buf[(*i)++] = *cp++;
518 	}
519 
520 }
521 
522 /*
523  * Return 1 if the string *want occurs in any of the strings
524  * in the NUL-terminated string list *have, or 0 otherwise.
525  * If either argument is NULL or empty, assume no filtering
526  * is desired and return 1.
527  */
528 static int
529 lstmatch(const char *want, const char *have)
530 {
531         if (want == NULL || have == NULL || *have == '\0')
532                 return 1;
533         while (*have != '\0') {
534                 if (strcasestr(have, want) != NULL)
535                         return 1;
536                 have = strchr(have, '\0') + 1;
537         }
538         return 0;
539 }
540 
541 /*
542  * Build a list of values taken by the macro im in the manual page.
543  */
544 static char *
545 buildoutput(size_t im, struct dbm_page *page)
546 {
547 	const char	*oldoutput, *sep, *input;
548 	char		*output, *newoutput, *value;
549 	size_t		 sz, i;
550 
551 	switch (im) {
552 	case KEY_Nd:
553 		return mandoc_strdup(page->desc);
554 	case KEY_Nm:
555 		input = page->name;
556 		break;
557 	case KEY_sec:
558 		input = page->sect;
559 		break;
560 	case KEY_arch:
561 		input = page->arch;
562 		if (input == NULL)
563 			input = "all\0";
564 		break;
565 	default:
566 		input = NULL;
567 		break;
568 	}
569 
570 	if (input != NULL) {
571 		sz = lstlen(input, 3) + 1;
572 		output = mandoc_malloc(sz);
573 		i = 0;
574 		lstcat(output, &i, input, " # ");
575 		output[i++] = '\0';
576 		assert(i == sz);
577 		return output;
578 	}
579 
580 	output = NULL;
581 	dbm_macro_bypage(im - 2, page->addr);
582 	while ((value = dbm_macro_next()) != NULL) {
583 		if (output == NULL) {
584 			oldoutput = "";
585 			sep = "";
586 		} else {
587 			oldoutput = output;
588 			sep = " # ";
589 		}
590 		mandoc_asprintf(&newoutput, "%s%s%s", oldoutput, sep, value);
591 		free(output);
592 		output = newoutput;
593 	}
594 	return output;
595 }
596 
597 /*
598  * Compile a set of string tokens into an expression.
599  * Tokens in "argv" are assumed to be individual expression atoms (e.g.,
600  * "(", "foo=bar", etc.).
601  */
602 static struct expr *
603 exprcomp(const struct mansearch *search, int argc, char *argv[], int *argi)
604 {
605 	struct expr	*parent, *child;
606 	int		 needterm, nested;
607 
608 	if ((nested = *argi) == argc)
609 		return NULL;
610 	needterm = 1;
611 	parent = child = NULL;
612 	while (*argi < argc) {
613 		if (strcmp(")", argv[*argi]) == 0) {
614 			if (needterm)
615 				warnx("missing term "
616 				    "before closing parenthesis");
617 			needterm = 0;
618 			if (nested)
619 				break;
620 			warnx("ignoring unmatched right parenthesis");
621 			++*argi;
622 			continue;
623 		}
624 		if (strcmp("-o", argv[*argi]) == 0) {
625 			if (needterm) {
626 				if (*argi > 0)
627 					warnx("ignoring -o after %s",
628 					    argv[*argi - 1]);
629 				else
630 					warnx("ignoring initial -o");
631 			}
632 			needterm = 1;
633 			++*argi;
634 			continue;
635 		}
636 		needterm = 0;
637 		if (child == NULL) {
638 			child = expr_and(search, argc, argv, argi);
639 			continue;
640 		}
641 		if (parent == NULL) {
642 			parent = mandoc_calloc(1, sizeof(*parent));
643 			parent->type = EXPR_OR;
644 			parent->next = NULL;
645 			parent->child = child;
646 		}
647 		child->next = expr_and(search, argc, argv, argi);
648 		child = child->next;
649 	}
650 	if (needterm && *argi)
651 		warnx("ignoring trailing %s", argv[*argi - 1]);
652 	return parent == NULL ? child : parent;
653 }
654 
655 static struct expr *
656 expr_and(const struct mansearch *search, int argc, char *argv[], int *argi)
657 {
658 	struct expr	*parent, *child;
659 	int		 needterm;
660 
661 	needterm = 1;
662 	parent = child = NULL;
663 	while (*argi < argc) {
664 		if (strcmp(")", argv[*argi]) == 0) {
665 			if (needterm)
666 				warnx("missing term "
667 				    "before closing parenthesis");
668 			needterm = 0;
669 			break;
670 		}
671 		if (strcmp("-o", argv[*argi]) == 0)
672 			break;
673 		if (strcmp("-a", argv[*argi]) == 0) {
674 			if (needterm) {
675 				if (*argi > 0)
676 					warnx("ignoring -a after %s",
677 					    argv[*argi - 1]);
678 				else
679 					warnx("ignoring initial -a");
680 			}
681 			needterm = 1;
682 			++*argi;
683 			continue;
684 		}
685 		if (needterm == 0)
686 			break;
687 		if (child == NULL) {
688 			child = exprterm(search, argc, argv, argi);
689 			if (child != NULL)
690 				needterm = 0;
691 			continue;
692 		}
693 		needterm = 0;
694 		if (parent == NULL) {
695 			parent = mandoc_calloc(1, sizeof(*parent));
696 			parent->type = EXPR_AND;
697 			parent->next = NULL;
698 			parent->child = child;
699 		}
700 		child->next = exprterm(search, argc, argv, argi);
701 		if (child->next != NULL) {
702 			child = child->next;
703 			needterm = 0;
704 		}
705 	}
706 	if (needterm && *argi)
707 		warnx("ignoring trailing %s", argv[*argi - 1]);
708 	return parent == NULL ? child : parent;
709 }
710 
711 static struct expr *
712 exprterm(const struct mansearch *search, int argc, char *argv[], int *argi)
713 {
714 	char		 errbuf[BUFSIZ];
715 	struct expr	*e;
716 	char		*key, *val;
717 	uint64_t	 iterbit;
718 	int		 cs, i, irc;
719 
720 	if (strcmp("(", argv[*argi]) == 0) {
721 		++*argi;
722 		e = exprcomp(search, argc, argv, argi);
723 		if (*argi < argc) {
724 			assert(strcmp(")", argv[*argi]) == 0);
725 			++*argi;
726 		} else
727 			warnx("unclosed parenthesis");
728 		return e;
729 	}
730 
731 	if (strcmp("-i", argv[*argi]) == 0 && *argi + 1 < argc) {
732 		cs = 0;
733 		++*argi;
734 	} else
735 		cs = 1;
736 
737 	e = mandoc_calloc(1, sizeof(*e));
738 	e->type = EXPR_TERM;
739 	e->bits = 0;
740 	e->next = NULL;
741 	e->child = NULL;
742 
743 	if (search->argmode == ARG_NAME) {
744 		e->bits = TYPE_Nm;
745 		e->match.type = DBM_EXACT;
746 		e->match.str = argv[(*argi)++];
747 		return e;
748 	}
749 
750 	/*
751 	 * Separate macro keys from search string.
752 	 * If needed, request regular expression handling.
753 	 */
754 
755 	if (search->argmode == ARG_WORD) {
756 		e->bits = TYPE_Nm;
757 		e->match.type = DBM_REGEX;
758 		mandoc_asprintf(&val, "[[:<:]]%s[[:>:]]", argv[*argi]);
759 		cs = 0;
760 	} else if ((val = strpbrk(argv[*argi], "=~")) == NULL) {
761 		e->bits = TYPE_Nm | TYPE_Nd;
762 		e->match.type = DBM_REGEX;
763 		val = argv[*argi];
764 		cs = 0;
765 	} else {
766 		if (val == argv[*argi])
767 			e->bits = TYPE_Nm | TYPE_Nd;
768 		if (*val == '=') {
769 			e->match.type = DBM_SUB;
770 			e->match.str = val + 1;
771 		} else
772 			e->match.type = DBM_REGEX;
773 		*val++ = '\0';
774 		if (strstr(argv[*argi], "arch") != NULL)
775 			cs = 0;
776 	}
777 
778 	/* Compile regular expressions. */
779 
780 	if (e->match.type == DBM_REGEX) {
781 		e->match.re = mandoc_malloc(sizeof(*e->match.re));
782 		irc = regcomp(e->match.re, val,
783 		    REG_EXTENDED | REG_NOSUB | (cs ? 0 : REG_ICASE));
784 		if (irc) {
785 			regerror(irc, e->match.re, errbuf, sizeof(errbuf));
786 			warnx("regcomp /%s/: %s", val, errbuf);
787 		}
788 		if (search->argmode == ARG_WORD)
789 			free(val);
790 		if (irc) {
791 			free(e->match.re);
792 			free(e);
793 			++*argi;
794 			return NULL;
795 		}
796 	}
797 
798 	if (e->bits) {
799 		++*argi;
800 		return e;
801 	}
802 
803 	/*
804 	 * Parse out all possible fields.
805 	 * If the field doesn't resolve, bail.
806 	 */
807 
808 	while (NULL != (key = strsep(&argv[*argi], ","))) {
809 		if ('\0' == *key)
810 			continue;
811 		for (i = 0, iterbit = 1; i < KEY_MAX; i++, iterbit <<= 1) {
812 			if (0 == strcasecmp(key, mansearch_keynames[i])) {
813 				e->bits |= iterbit;
814 				break;
815 			}
816 		}
817 		if (i == KEY_MAX) {
818 			if (strcasecmp(key, "any"))
819 				warnx("treating unknown key "
820 				    "\"%s\" as \"any\"", key);
821 			e->bits |= ~0ULL;
822 		}
823 	}
824 
825 	++*argi;
826 	return e;
827 }
828 
829 static void
830 exprfree(struct expr *e)
831 {
832 	if (e->next != NULL)
833 		exprfree(e->next);
834 	if (e->child != NULL)
835 		exprfree(e->child);
836 	free(e);
837 }
838