Adding upstream version 2.12.0.upstream/2.12.0

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 1018 insertions, 0 deletions

diff --git a/src/check_mandirs.c b/src/check_mandirs.c
new file mode 100644
index 0000000..75c6f5e
--- /dev/null
+++ b/src/check_mandirs.c
@@ -0,0 +1,1018 @@
+/*
+ * check_mandirs.c: used to auto-update the database caches
+ *
+ * Copyright (C) 1994, 1995 Graeme W. Wilford. (Wilf.)
+ * Copyright (C) 2001, 2002, 2003, 2004, 2007, 2008, 2009, 2010, 2011
+ *               Colin Watson.
+ *
+ * This file is part of man-db.
+ *
+ * man-db is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * man-db is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with man-db; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
+ *
+ * Mon May  2 17:36:33 BST 1994  Wilf. (G.Wilford@ee.surrey.ac.uk)
+ *
+ * CJW: Many changes to whatis parsing. Added database purging.
+ * See ChangeLog for details.
+ */
+
+#ifdef HAVE_CONFIG_H
+#  include "config.h"
+#endif /* HAVE_CONFIG_H */
+
+#include <assert.h>
+#include <stdbool.h>
+#include <string.h>
+#include <stdlib.h>
+#include <stdio.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <time.h>
+#include <errno.h>
+#include <ctype.h>
+#include <dirent.h>
+#include <unistd.h>
+
+#include "attribute.h"
+#include "dirname.h"
+#include "error.h"
+#include "gl_array_list.h"
+#include "gl_hash_map.h"
+#include "gl_xlist.h"
+#include "gl_xmap.h"
+#include "stat-time.h"
+#include "timespec.h"
+#include "xalloc.h"
+#include "xvasprintf.h"
+
+#include "gettext.h"
+#define _(String) gettext (String)
+
+#include "manconfig.h"
+
+#include "appendstr.h"
+#include "compression.h"
+#include "debug.h"
+#include "fatal.h"
+#include "filenames.h"
+#include "glcontainers.h"
+#include "orderfiles.h"
+#include "security.h"
+#include "util.h"
+
+#include "mydbm.h"
+#include "db_storage.h"
+
+#include "descriptions.h"
+#include "globbing.h"
+#include "lexgrog.h"
+#include "manp.h"
+#include "ult_src.h"
+#include "check_mandirs.h"
+
+bool opt_test;		/* don't update db */
+int pages;
+bool force_rescan = false;
+
+gl_map_t whatis_map = NULL;
+
+struct whatis {
+	char *whatis;
+	char *filters;
+};
+
+static void whatis_free (const void *value)
+{
+	struct whatis *whatis = (struct whatis *) value;
+
+	free (whatis->whatis);
+	free (whatis->filters);
+	free (whatis);
+}
+
+static void gripe_multi_extensions (const char *path, const char *sec,
+				    const char *name, const char *ext)
+{
+	if (quiet < 2)
+		error (0, 0,
+		       _("warning: %s/man%s/%s.%s*: competing extensions"),
+		       path, sec, name, ext);
+}
+
+/* Test whether an errno value is EAGAIN or (on systems where it differs)
+ * EWOULDBLOCK.  This is a separate function mainly in order to be able to
+ * control GCC diagnostics in one place.
+ */
+#pragma GCC diagnostic push
+#pragma GCC diagnostic ignored "-Wlogical-op"
+static inline bool is_eagain (int err)
+{
+	return err == EAGAIN || err == EWOULDBLOCK;
+}
+#pragma GCC diagnostic pop
+
+static void gripe_rwopen_failed (MYDBM_FILE dbf)
+{
+	if (errno == EACCES || errno == EROFS)
+		debug ("database %s is read-only\n", dbf->name);
+	else if (is_eagain (errno))
+		debug ("database %s is locked by another process\n", dbf->name);
+	else {
+#ifdef MAN_DB_UPDATES
+		if (!quiet)
+#endif /* MAN_DB_UPDATES */
+			error (0, errno, _("can't update index cache %s"),
+			       dbf->name);
+	}
+}
+
+static bool ensure_db_open (MYDBM_FILE dbf)
+{
+	if (dbf->file)
+		return true;
+	if (!MYDBM_RWOPEN (dbf))
+		return false;
+	return true;
+}
+
+/* Take absolute filename and path (for ult_src) and do sanity checks on
+ * file. Also check that file is non-zero in length and is not already in
+ * the db. If not, find its ult_src() and see if we have the whatis cached,
+ * otherwise cache it in case we trace another manpage back to it. Next,
+ * store it in the db along with any references found in the whatis.
+ */
+void test_manfile (MYDBM_FILE dbf, const char *file, const char *path)
+{
+	char *manpage_base;
+	const struct ult_value *ult;
+	struct lexgrog lg;
+	struct mandata *info, *exists;
+	struct compression *comp;
+	struct stat buf;
+	size_t len;
+	const struct whatis *whatis;
+
+	debug ("\ntest_manfile: considering %s\n", file);
+
+	memset (&lg, 0, sizeof (struct lexgrog));
+
+	info = filename_info (file, quiet < 2);
+	if (!info)
+		return;
+	manpage_base = info->name; /* steal memory */
+	info->name = NULL;
+
+	comp = comp_info (file, true);
+	if (comp) {
+		len = strlen (comp->stem);
+		free (comp->stem);
+	} else
+		len = strlen (file);
+
+	/* to get mtime info */
+	(void) lstat (file, &buf);
+	info->mtime = get_stat_mtime (&buf);
+
+	/* check that our file actually contains some data */
+	if (buf.st_size == 0) {
+		/* man-db pre 2.3 place holder ? */
+		free_mandata_struct (info);
+		return;
+	}
+
+	/* Check for multiple pages whose details match except for having
+	 * different compression extensions.
+	 */
+	exists = dblookup_exact (dbf, manpage_base, info->ext, true);
+	if (exists && !STREQ (exists->comp, info->comp ? info->comp : "-")) {
+		char *abs_filename;
+
+		/* If the cached file still exists, then we have a collision:
+		 * two pages that only differ by compression extension.
+		 */
+		abs_filename = make_filename (path, NULL, exists, "man");
+		if (!abs_filename) {
+			if (!opt_test)
+				dbdelete (dbf, manpage_base, exists);
+		} else {
+			gripe_multi_extensions (path, exists->sec,
+						manpage_base, exists->ext);
+			free (abs_filename);
+			free_mandata_struct (exists);
+			free_mandata_struct (info);
+			return;
+		}
+	}
+	free_mandata_struct (exists);
+
+	/* Trace the file to its ultimate source, otherwise we'll be
+	 * looking for whatis info in files containing only '.so
+	 * manx/foo.x', which will give us an unobtainable whatis
+	 * for the entry. */
+	ult = ult_src (file, path, &buf, SO_LINK | SOFT_LINK | HARD_LINK);
+
+	if (!ult) {
+		if (quiet < 2)
+			error (0, 0,
+			       _("warning: %s: bad symlink or ROFF `.so' request"),
+			       file);
+		free_mandata_struct (info);
+		return;
+	}
+
+	pages++;			/* pages seen so far */
+
+	if (strncmp (ult->path, file, len) == 0)
+		info->id = ULT_MAN;	/* ultimate source file */
+	else
+		info->id = SO_MAN;	/* .so, sym or hard linked file */
+
+	/* Ok, here goes: Use a hash tree to store the ult_srcs with
+	 * their whatis. Anytime after, check the hash tree, if it's there,
+	 * use it. This saves us a find_name() which is a real hog.
+	 *
+	 * Use the full path in ult->path as the hash key so we don't have
+	 * to clear the hash between calls.
+	 */
+
+	if (!whatis_map)
+		whatis_map = new_string_map (GL_HASH_MAP, whatis_free);
+
+	whatis = gl_map_get (whatis_map, ult->path);
+	if (whatis) {
+		lg.whatis = whatis->whatis ? xstrdup (whatis->whatis) : NULL;
+		lg.filters =
+			whatis->filters ? xstrdup (whatis->filters) : NULL;
+	} else {
+		/* Cache miss; go and get the whatis info in its raw state. */
+		char *file_base = base_name (file);
+		struct whatis *new_whatis;
+
+		if (!STRNEQ (ult->path, file, len))
+			debug ("test_manfile: link not in cache:\n"
+			       " source = %s\n"
+			       " target = %s\n", file, ult->path);
+
+		lg.type = MANPAGE;
+		drop_effective_privs ();
+		find_name (ult->path, file_base, &lg, NULL);
+		free (file_base);
+		regain_effective_privs ();
+
+		new_whatis = XMALLOC (struct whatis);
+		new_whatis->whatis = lg.whatis ? xstrdup (lg.whatis) : NULL;
+		new_whatis->filters = lg.filters ? xstrdup (lg.filters) : NULL;
+		gl_map_put (whatis_map, xstrdup (ult->path), new_whatis);
+	}
+
+	debug ("\"%s\"\n", lg.whatis);
+
+	/* split up the raw whatis data and store references */
+	info->pointer = NULL;	/* direct page, so far */
+	info->filter = lg.filters;
+	if (lg.whatis) {
+		gl_list_t descs = parse_descriptions (manpage_base, lg.whatis);
+		if (!opt_test)
+			store_descriptions (dbf, descs, info, path,
+					    manpage_base, ult->trace);
+		gl_list_free (descs);
+	} else if (quiet < 2) {
+		(void) stat (ult->path, &buf);
+		if (buf.st_size == 0)
+			error (0, 0, _("warning: %s: ignoring empty file"),
+			       ult->path);
+		else
+			error (0, 0,
+			       _("warning: %s: whatis parse for %s(%s) failed"),
+			       ult->path, manpage_base, info->ext);
+	}
+
+	free_mandata_struct (info);
+	free (lg.whatis);
+}
+
+static void add_dir_entries (MYDBM_FILE dbf, const char *path, char *infile)
+{
+	char *manpage;
+	int len;
+	struct dirent *newdir;
+	DIR *dir;
+	gl_list_t names;
+	const char *name;
+
+	manpage = xasprintf ("%s/%s/", path, infile);
+	assert (manpage);
+	len = strlen (manpage);
+
+	/*
+	 * All filename entries in this dir should either be valid manpages
+	 * or . files (such as current, parent dir).
+	 */
+
+	dir = opendir (infile);
+	if (!dir) {
+		error (0, errno, _("can't search directory %s"), manpage);
+		free (manpage);
+                return;
+        }
+
+	names = new_string_list (GL_ARRAY_LIST, false);
+
+        /* strlen(newdir->d_name) could be replaced by newdir->d_reclen */
+
+	while ((newdir = readdir (dir)) != NULL) {
+		if (*newdir->d_name == '.' &&
+		    strlen (newdir->d_name) < (size_t) 3)
+			continue;
+		gl_list_add_last (names, xstrdup (newdir->d_name));
+	}
+	closedir (dir);
+
+	order_files (infile, &names);
+
+	GL_LIST_FOREACH (names, name) {
+		manpage = appendstr (manpage, name, (void *) 0);
+		test_manfile (dbf, manpage, path);
+		*(manpage + len) = '\0';
+	}
+
+	gl_list_free (names);
+	free (manpage);
+}
+
+#ifdef MAN_OWNER
+extern uid_t uid;			/* current effective user id */
+extern gid_t gid;			/* current effective group id */
+
+/* Fix a path's ownership if possible and necessary. */
+void chown_if_possible (const char *path)
+{
+	struct stat st;
+	struct passwd *man_owner = get_man_owner ();
+
+	if (lstat (path, &st) != 0)
+		return;
+
+	if ((uid == 0 ||
+	     (uid == man_owner->pw_uid && st.st_uid == man_owner->pw_uid &&
+	      gid == man_owner->pw_gid)) &&
+	    (st.st_uid != man_owner->pw_uid ||
+	     st.st_gid != man_owner->pw_gid)) {
+		debug ("fixing ownership of %s\n", path);
+		if (lchown (path, man_owner->pw_uid, man_owner->pw_gid) < 0)
+			fatal (0, _("can't chown %s"), path);
+	}
+}
+#else /* !MAN_OWNER */
+void chown_if_possible (const char *path MAYBE_UNUSED)
+{
+}
+#endif /* MAN_OWNER */
+
+/* create the catman hierarchy if it doesn't exist */
+static void mkcatdirs (const char *mandir, const char *catdir)
+{
+	char *manname, *catname;
+
+	if (catdir) {
+		int oldmask = umask (022);
+		/* first the base catdir */
+		if (is_directory (catdir) != 1) {
+			regain_effective_privs ();
+			if (mkdir (catdir, 0755) < 0) {
+				if (!quiet)
+					error (0, 0,
+					       _("warning: cannot create catdir %s"),
+					       catdir);
+				debug ("warning: cannot create catdir %s\n",
+				       catdir);
+			} else
+				debug ("created base catdir %s\n", catdir);
+			chown_if_possible (catdir);
+			drop_effective_privs ();
+		}
+		/* then the hierarchy */
+		catname = xasprintf ("%s/cat1", catdir);
+		manname = xasprintf ("%s/man1", mandir);
+		if (is_directory (catdir) == 1) {
+			int j;
+			regain_effective_privs ();
+			debug ("creating catdir hierarchy %s	", catdir);
+			for (j = 1; j <= 9; j++) {
+				catname[strlen (catname) - 1] = '0' + j;
+				manname[strlen (manname) - 1] = '0' + j;
+				if ((is_directory (manname) == 1)
+				 && (is_directory (catname) != 1)) {
+					if (mkdir (catname, 0755) < 0) {
+						if (!quiet)
+							error (0, 0, _("warning: cannot create catdir %s"), catname);
+						debug ("warning: cannot create catdir %s\n", catname);
+					} else
+						debug (" cat%d", j);
+					chown_if_possible (catname);
+				}
+			}
+			debug ("\n");
+			drop_effective_privs ();
+		}
+		free (catname);
+		free (manname);
+		umask (oldmask);
+	}
+}
+
+/* We used to install cat directories with the setgid bit set, but this
+ * wasn't very useful and introduces the ability to escalate privileges to
+ * that group:
+ *   https://www.halfdog.net/Security/2015/SetgidDirectoryPrivilegeEscalation/
+ */
+static void fix_permissions (const char *dir)
+{
+	struct stat st;
+
+	if (stat (dir, &st) == 0) {
+		if ((st.st_mode & S_ISGID) != 0) {
+			int status;
+
+			debug ("removing setgid bit from %s\n", dir);
+			status = chmod (dir, st.st_mode & ~S_ISGID);
+			if (status)
+				error (0, errno, _("can't chmod %s"), dir);
+		}
+
+		chown_if_possible (dir);
+	}
+}
+
+static void fix_permissions_tree (const char *catdir)
+{
+	if (is_directory (catdir) == 1) {
+		char *catname;
+		int i;
+
+		fix_permissions (catdir);
+		catname = xasprintf ("%s/cat1", catdir);
+		assert (catname);
+		for (i = 1; i <= 9; ++i) {
+			catname[strlen (catname) - 1] = '0' + i;
+			fix_permissions (catname);
+		}
+		free (catname);
+	}
+}
+
+/*
+ * accepts the raw man dir tree eg. "/usr/man" and the time stored in the db
+ * any dirs of the tree that have been modified (ie added to) will then be
+ * scanned for new files, which are then added to the db.
+ */
+static int testmandirs (MYDBM_FILE dbf, const char *path, const char *catpath,
+			struct timespec last, bool create)
+{
+	DIR *dir;
+	struct dirent *mandir;
+	int amount = 0;
+	bool created = false;
+
+	debug ("Testing %s for new files\n", path);
+
+	if (catpath)
+		fix_permissions_tree (catpath);
+
+	dir = opendir (path);
+	if (!dir) {
+		error (0, errno, _("can't search directory %s"), path);
+		return 0;
+	}
+
+	if (chdir (path) != 0) {
+		error (0, errno, _("can't change to directory %s"), path);
+		closedir (dir);
+		return 0;
+	}
+
+	while( (mandir = readdir (dir)) ) {
+		struct stat stbuf;
+		struct timespec mtime;
+
+		if (strncmp (mandir->d_name, "man", 3) != 0)
+			continue;
+
+		debug ("Examining %s\n", mandir->d_name);
+
+		if (stat (mandir->d_name, &stbuf) != 0)	/* stat failed */
+			continue;
+		if (!S_ISDIR(stbuf.st_mode))		/* not a directory */
+			continue;
+		mtime = get_stat_mtime (&stbuf);
+		if (last.tv_sec && timespec_cmp (mtime, last) <= 0) {
+			/* scanned already */
+			debug ("%s modified %ld.%09ld, "
+			       "db modified %ld.%09ld\n",
+			       mandir->d_name,
+			       (long) mtime.tv_sec, (long) mtime.tv_nsec,
+			       (long) last.tv_sec, (long) last.tv_nsec);
+			continue;
+		}
+
+		debug ("\tsubdirectory %s has been 'modified'\n",
+		       mandir->d_name);
+
+		if (create && !created) {
+			/* We seem to have something to do, so create the
+			 * database now.
+			 */
+			mkcatdirs (path, catpath);
+
+			/* Open the db in CTRW mode to store the $ver$ ID */
+
+			if (!MYDBM_CTRWOPEN (dbf)) {
+				if (errno == EACCES || errno == EROFS) {
+					debug ("database %s is read-only\n",
+					       dbf->name);
+					closedir (dir);
+					return 0;
+				} else {
+					error (0, errno,
+					       _("can't create index cache %s"),
+					       dbf->name);
+					closedir (dir);
+					return -1;
+				}
+			}
+
+			dbver_wr (dbf);
+
+			created = true;
+		} else if (!ensure_db_open (dbf)) {
+			gripe_rwopen_failed (dbf);
+			closedir (dir);
+			return 0;
+		}
+
+		if (!quiet) {
+			int tty = isatty (STDERR_FILENO);
+
+			if (tty)
+				fprintf (stderr, "\r");
+			fprintf (stderr,
+				 _("Updating index cache for path "
+				   "`%s/%s'. Wait..."), path, mandir->d_name);
+			if (!tty)
+				fprintf (stderr, "\n");
+		}
+		add_dir_entries (dbf, path, mandir->d_name);
+		amount++;
+	}
+	closedir (dir);
+
+	return amount;
+}
+
+/* routine to prepare/create the db prior to calling testmandirs() */
+int create_db (MYDBM_FILE dbf, const char *manpath, const char *catpath)
+{
+	struct timespec time_zero;
+	int amount;
+
+	debug ("create_db(%s): %s\n", manpath, dbf->name);
+
+	time_zero.tv_sec = 0;
+	time_zero.tv_nsec = 0;
+	amount = testmandirs (dbf, manpath, catpath, time_zero, true);
+
+	if (amount > 0 && !quiet)
+		fputs (_("done.\n"), stderr);
+
+	return amount;
+}
+
+/* Make sure an existing database is essentially sane. */
+static bool sanity_check_db (MYDBM_FILE dbf)
+{
+	datum key;
+
+	if (dbver_rd (dbf))
+		return false;
+
+	key = MYDBM_FIRSTKEY (dbf);
+	while (MYDBM_DPTR (key) != NULL) {
+		datum content, nextkey;
+
+		content = MYDBM_FETCH (dbf, key);
+		if (!MYDBM_DPTR (content)) {
+			debug ("warning: %s has a key with no content (%s); "
+			       "rebuilding\n", dbf->name, MYDBM_DPTR (key));
+			MYDBM_FREE_DPTR (key);
+			return false;
+		}
+#pragma GCC diagnostic push
+#if GNUC_PREREQ(10,0)
+#  pragma GCC diagnostic ignored "-Wanalyzer-double-free"
+#endif
+		MYDBM_FREE_DPTR (content);
+		nextkey = MYDBM_NEXTKEY (dbf, key);
+		MYDBM_FREE_DPTR (key);
+#pragma GCC diagnostic pop
+		key = nextkey;
+	}
+
+	return true;
+}
+
+/* routine to update the db, ensure that it is consistent with the
+   filesystem */
+int update_db (MYDBM_FILE dbf, const char *manpath, const char *catpath)
+{
+	struct timespec mtime;
+	int new;
+
+	if (!ensure_db_open (dbf) || !sanity_check_db (dbf)) {
+		debug ("failed to open %s O_RDONLY\n", dbf->name);
+		return -1;
+	}
+	mtime = MYDBM_GET_TIME (dbf);
+
+	debug ("update_db(): %ld.%09ld\n",
+	       (long) mtime.tv_sec, (long) mtime.tv_nsec);
+	new = testmandirs (dbf, manpath, catpath, mtime, false);
+
+	if (new > 0 && !quiet)
+		fputs (_("done.\n"), stderr);
+
+	return new;
+}
+
+/* Purge any entries pointing to name. This currently assumes that pointers
+ * are always shallow, which may not be a good assumption yet; it should be
+ * close, though.
+ */
+void purge_pointers (MYDBM_FILE dbf, const char *name)
+{
+	datum key = MYDBM_FIRSTKEY (dbf);
+
+	debug ("Purging pointers to vanished page \"%s\"\n", name);
+
+	while (MYDBM_DPTR (key) != NULL) {
+		datum content, nextkey;
+		struct mandata *entry = NULL;
+		char *nicekey, *tab;
+
+#pragma GCC diagnostic push
+#if GNUC_PREREQ(10,0)
+#  pragma GCC diagnostic ignored "-Wanalyzer-use-after-free"
+#endif
+		/* Ignore db identifier keys. */
+		if (*MYDBM_DPTR (key) == '$')
+			goto pointers_next;
+#pragma GCC diagnostic pop
+
+		content = MYDBM_FETCH (dbf, key);
+		if (!MYDBM_DPTR (content))
+			return;
+
+		/* Get just the name. */
+		nicekey = xstrdup (MYDBM_DPTR (key));
+		tab = strchr (nicekey, '\t');
+		if (tab)
+			*tab = '\0';
+
+#pragma GCC diagnostic push
+#if GNUC_PREREQ(10,0)
+#  pragma GCC diagnostic ignored "-Wanalyzer-use-after-free"
+#endif
+		if (*MYDBM_DPTR (content) == '\t')
+			goto pointers_contentnext;
+#pragma GCC diagnostic pop
+
+		entry = split_content (dbf, MYDBM_DPTR (content));
+		if (entry->id != SO_MAN && entry->id != WHATIS_MAN)
+			goto pointers_contentnext;
+
+		if (STREQ (entry->pointer, name)) {
+			if (!opt_test)
+				dbdelete (dbf, nicekey, entry);
+			else
+				debug ("%s(%s): pointer vanished, "
+				       "would delete\n", nicekey, entry->ext);
+		}
+
+pointers_contentnext:
+		free_mandata_struct (entry);
+		free (nicekey);
+		MYDBM_FREE_DPTR (content);
+pointers_next:
+		nextkey = MYDBM_NEXTKEY (dbf, key);
+		MYDBM_FREE_DPTR (key);
+		key = nextkey;
+	}
+}
+
+/* Count the number of exact extension matches returned from look_for_file()
+ * (which may return inexact extension matches in some cases). It may turn
+ * out that this is better handled in look_for_file() itself.
+ */
+static int count_glob_matches (const char *ext, gl_list_t source,
+			       struct timespec db_mtime)
+{
+	const char *walk;
+	int count = 0;
+
+	GL_LIST_FOREACH (source, walk) {
+		struct mandata *info;
+		struct stat statbuf;
+
+		if (stat (walk, &statbuf) == -1) {
+			debug ("count_glob_matches: excluding %s "
+			       "because stat failed\n", walk);
+			continue;
+		}
+		if (db_mtime.tv_sec != (time_t) -1 &&
+		    timespec_cmp (get_stat_mtime (&statbuf), db_mtime) <= 0) {
+			debug ("count_glob_matches: excluding %s, "
+			       "no newer than database\n", walk);
+			continue;
+		}
+
+		info = filename_info (walk, quiet < 2);
+		if (info) {
+			if (STREQ (ext, info->ext))
+				++count;
+			free_mandata_struct (info);
+		}
+	}
+
+	return count;
+}
+
+/* Decide whether to purge a reference to a "normal" (ULT_MAN or SO_MAN)
+ * page.
+ */
+static int purge_normal (MYDBM_FILE dbf, const char *name,
+			 struct mandata *info, gl_list_t found)
+{
+	struct timespec t;
+
+	/* TODO: On some systems, the cat page extension differs from the
+	 * man page extension, so this may be too strict.
+	 */
+	t.tv_sec = -1;
+	t.tv_nsec = -1;
+	if (count_glob_matches (info->ext, found, t))
+		return 0;
+
+	if (!opt_test)
+		dbdelete (dbf, name, info);
+	else
+		debug ("%s(%s): missing page, would delete\n",
+		       name, info->ext);
+
+	return 1;
+}
+
+/* Decide whether to purge a reference to a WHATIS_MAN or WHATIS_CAT page. */
+static int purge_whatis (MYDBM_FILE dbf, const char *path, bool cat,
+			 const char *name, struct mandata *info,
+			 gl_list_t found, struct timespec db_mtime)
+{
+	/* TODO: On some systems, the cat page extension differs from the
+	 * man page extension, so this may be too strict.
+	 */
+	if (count_glob_matches (info->ext, found, db_mtime)) {
+		/* If the page exists and didn't beforehand, then presumably
+		 * we're about to rescan, which will replace the WHATIS_MAN
+		 * entry with something better. However, there have been
+		 * bugs that created false WHATIS_MAN entries, so force the
+		 * rescan just to be sure; since in the absence of a bug we
+		 * would rescan anyway, this isn't a problem.
+		 */
+		if (!force_rescan)
+			debug ("%s(%s): whatis replaced by real page; "
+			       "forcing a rescan just in case\n",
+			       name, info->ext);
+		force_rescan = true;
+		return 0;
+	} else if (STREQ (info->pointer, "-")) {
+		/* This is broken; a WHATIS_MAN should never have an empty
+		 * pointer field. This might have happened due to the first
+		 * name in a page being different from what the file name
+		 * says; that's fixed now, so delete and force a rescan.
+		 */
+		if (!opt_test)
+			dbdelete (dbf, name, info);
+		else
+			debug ("%s(%s): whatis with empty pointer, "
+			       "would delete\n", name, info->ext);
+
+		if (!force_rescan)
+			debug ("%s(%s): whatis had empty pointer; "
+			       "forcing a rescan just in case\n",
+			       name, info->ext);
+		force_rescan = true;
+		return 1;
+	} else {
+		/* Does the real page still exist? */
+		gl_list_t real_found;
+		bool save_debug = debug_level;
+		struct timespec t;
+		int count;
+
+		debug_level = false;
+		real_found = look_for_file (path, info->ext,
+					    info->pointer, cat, LFF_MATCHCASE);
+		debug_level = save_debug;
+
+		t.tv_sec = -1;
+		t.tv_nsec = -1;
+		count = count_glob_matches (info->ext, real_found, t);
+		gl_list_free (real_found);
+		if (count)
+			return 0;
+
+		if (!opt_test)
+			dbdelete (dbf, name, info);
+		else
+			debug ("%s(%s): whatis target was deleted, "
+			       "would delete\n", name, info->ext);
+		return 1;
+	}
+}
+
+/* Check that multi keys are correctly constructed. */
+static bool check_multi_key (const char *name, const char *content)
+{
+	const char *walk, *next;
+
+	if (!*content)
+		return false;
+
+	for (walk = content; walk && *walk; walk = next) {
+		/* The name in the multi key should only differ from the
+		 * name of the key itself in its case, if at all.
+		 */
+		bool valid = true;
+		++walk; /* skip over initial tab */
+		next = strchr (walk, '\t');
+		if (next) {
+			if (strncasecmp (name, walk, next - walk))
+				valid = false;
+		} else {
+			if (strcasecmp (name, walk))
+				valid = false;
+		}
+		if (!valid) {
+			debug ("%s: broken multi key \"%s\", "
+			       "forcing a rescan\n", name, content);
+			force_rescan = true;
+			return true;
+		}
+
+		/* If the name was valid, skip over the extension and
+		 * continue the scan.
+		 */
+		walk = next;
+		next = walk ? strchr (walk + 1, '\t') : NULL;
+	}
+
+	return false;
+}
+
+/* Go through the database and purge references to man pages that no longer
+ * exist.
+ */
+int purge_missing (MYDBM_FILE dbf, const char *manpath, const char *catpath)
+{
+#ifdef NDBM
+	char *dirfile;
+#endif
+	struct stat st;
+	bool db_exists;
+	datum key;
+	int count = 0;
+	struct timespec db_mtime;
+
+#ifdef NDBM
+	dirfile = xasprintf ("%s.dir", dbf->name);
+	db_exists = stat (dirfile, &st) == 0;
+	free (dirfile);
+#else
+	db_exists = stat (dbf->name, &st) == 0;
+#endif
+	if (!db_exists)
+		/* nothing to purge */
+		return 0;
+
+	if (!quiet)
+		printf (_("Purging old database entries in %s...\n"), manpath);
+
+	if (!ensure_db_open (dbf) || !sanity_check_db (dbf)) {
+		gripe_rwopen_failed (dbf);
+		return 0;
+	}
+	db_mtime = MYDBM_GET_TIME (dbf);
+
+	key = MYDBM_FIRSTKEY (dbf);
+
+	while (MYDBM_DPTR (key) != NULL) {
+		datum content, nextkey;
+		struct mandata *entry;
+		char *nicekey, *tab;
+		bool save_debug;
+		gl_list_t found;
+
+#pragma GCC diagnostic push
+#if GNUC_PREREQ(10,0)
+#  pragma GCC diagnostic ignored "-Wanalyzer-use-after-free"
+#endif
+		/* Ignore db identifier keys. */
+		if (*MYDBM_DPTR (key) == '$') {
+			nextkey = MYDBM_NEXTKEY (dbf, key);
+			MYDBM_FREE_DPTR (key);
+			key = nextkey;
+			continue;
+		}
+#pragma GCC diagnostic pop
+
+		content = MYDBM_FETCH (dbf, key);
+		if (!MYDBM_DPTR (content)) {
+			nextkey = MYDBM_NEXTKEY (dbf, key);
+			MYDBM_FREE_DPTR (key);
+			key = nextkey;
+			continue;
+		}
+
+		/* Get just the name. */
+		nicekey = xstrdup (MYDBM_DPTR (key));
+		tab = strchr (nicekey, '\t');
+		if (tab)
+			*tab = '\0';
+
+#pragma GCC diagnostic push
+#if GNUC_PREREQ(10,0)
+#  pragma GCC diagnostic ignored "-Wanalyzer-use-after-free"
+#endif
+		/* Deal with multi keys. */
+		if (*MYDBM_DPTR (content) == '\t') {
+			if (check_multi_key (nicekey, MYDBM_DPTR (content)))
+				MYDBM_DELETE (dbf, key);
+			free (nicekey);
+			MYDBM_FREE_DPTR (content);
+			nextkey = MYDBM_NEXTKEY (dbf, key);
+			MYDBM_FREE_DPTR (key);
+			key = nextkey;
+			continue;
+		}
+#pragma GCC diagnostic pop
+
+		entry = split_content (dbf, MYDBM_DPTR (content));
+
+		save_debug = debug_level;
+		debug_level = false;	/* look_for_file() is quite noisy */
+		if (entry->id <= WHATIS_MAN)
+			found = look_for_file (manpath, entry->ext,
+					       entry->name ? entry->name
+							   : nicekey,
+					       false, LFF_MATCHCASE);
+		else
+			found = look_for_file (catpath, entry->ext,
+					       entry->name ? entry->name
+							   : nicekey,
+					       true, LFF_MATCHCASE);
+		debug_level = save_debug;
+
+		/* Now actually decide whether to purge, depending on the
+		 * type of entry.
+		 */
+		if (entry->id == ULT_MAN || entry->id == SO_MAN ||
+		    entry->id == STRAY_CAT)
+			count += purge_normal (dbf, nicekey, entry, found);
+		else if (entry->id == WHATIS_MAN)
+			count += purge_whatis (dbf, manpath, false, nicekey,
+					       entry, found, db_mtime);
+		else	/* entry->id == WHATIS_CAT */
+			count += purge_whatis (dbf, catpath, true, nicekey,
+					       entry, found, db_mtime);
+
+		gl_list_free (found);
+		free (nicekey);
+
+		free_mandata_struct (entry);
+		MYDBM_FREE_DPTR (content);
+		nextkey = MYDBM_NEXTKEY (dbf, key);
+		MYDBM_FREE_DPTR (key);
+		key = nextkey;
+	}
+
+	return count;
+}