Never call qsort on potentially NULL arrays

This extends 62678ded 'efi: never call qsort on potentially
NULL arrays' to all other places where qsort is used and it
is not obvious that the count is non-zero.

src/analyze/systemd-analyze.c

@@ -768,7 +768,7 @@ static int list_dependencies_one(DBusConnection *bus, const char *name, unsigned
         if (r < 0)
                 return r;
 
-        qsort(deps, strv_length(deps), sizeof (char*), list_dependencies_compare);
+        qsort_safe(deps, strv_length(deps), sizeof (char*), list_dependencies_compare);
 
         r = acquire_boot_times(bus, &boot);
         if (r < 0)

src/cgtop/cgtop.c

@@ -461,7 +461,7 @@ static int display(Hashmap *a) {
                 if (g->n_tasks_valid || g->cpu_valid || g->memory_valid || g->io_valid)
                         array[n++] = g;
 
-        qsort(array, n, sizeof(Group*), group_compare);
+        qsort_safe(array, n, sizeof(Group*), group_compare);
 
         /* Find the longest names in one run */
         for (j = 0; j < n; j++) {

src/core/namespace.c

@@ -222,7 +222,7 @@ int setup_namespace(char** read_write_dirs,
                      strv_length(read_only_dirs) +
                      strv_length(inaccessible_dirs) +
                      (private_tmp ? 2 : 0);
-        BindMount *m, *mounts;
+        BindMount *m, *mounts = NULL;
         int r = 0;
 
         if (!mount_flags)
@@ -231,27 +231,29 @@ int setup_namespace(char** read_write_dirs,
         if (unshare(CLONE_NEWNS) < 0)
                 return -errno;
 
-        m = mounts = (BindMount *) alloca(n * sizeof(BindMount));
-        if ((r = append_mounts(&m, read_write_dirs, READWRITE)) < 0 ||
-                (r = append_mounts(&m, read_only_dirs, READONLY)) < 0 ||
-                (r = append_mounts(&m, inaccessible_dirs, INACCESSIBLE)) < 0)
-                return r;
+        if (n) {
+                m = mounts = (BindMount *) alloca(n * sizeof(BindMount));
+                if ((r = append_mounts(&m, read_write_dirs, READWRITE)) < 0 ||
+                    (r = append_mounts(&m, read_only_dirs, READONLY)) < 0 ||
+                    (r = append_mounts(&m, inaccessible_dirs, INACCESSIBLE)) < 0)
+                        return r;
 
-        if (private_tmp) {
-                m->path = "/tmp";
-                m->mode = PRIVATE_TMP;
-                m++;
+                if (private_tmp) {
+                        m->path = "/tmp";
+                        m->mode = PRIVATE_TMP;
+                        m++;
 
-                m->path = "/var/tmp";
-                m->mode = PRIVATE_VAR_TMP;
-                m++;
+                        m->path = "/var/tmp";
+                        m->mode = PRIVATE_VAR_TMP;
+                        m++;
+                }
+
+                assert(mounts + n == m);
+
+                qsort(mounts, n, sizeof(BindMount), mount_path_compare);
+                drop_duplicates(mounts, &n);
         }
 
-        assert(mounts + n == m);
-
-        qsort(mounts, n, sizeof(BindMount), mount_path_compare);
-        drop_duplicates(mounts, &n);
-
         /* Remount / as SLAVE so that nothing now mounted in the namespace
            shows up in the parent */
         if (mount(NULL, "/", NULL, MS_SLAVE|MS_REC, NULL) < 0)

src/journal/catalog.c

@@ -399,7 +399,7 @@ int catalog_update(const char* database, const char* root, const char* const* di
         }
 
         assert(n == hashmap_size(h));
-        qsort(items, n, sizeof(CatalogItem), catalog_compare_func);
+        qsort_safe(items, n, sizeof(CatalogItem), catalog_compare_func);
 
         r = write_catalog(database, h, sb, items, n);
         if (r < 0)

src/journal/journal-file.c

@@ -1344,7 +1344,7 @@ int journal_file_append_entry(JournalFile *f, const dual_timestamp *ts, const st
 
         /* Order by the position on disk, in order to improve seek
          * times for rotating media. */
-        qsort(items, n_iovec, sizeof(EntryItem), entry_item_cmp);
+        qsort_safe(items, n_iovec, sizeof(EntryItem), entry_item_cmp);
 
         r = journal_file_append_entry_internal(f, ts, xor_hash, items, n_iovec, seqnum, ret, offset);
 

src/journal/journal-vacuum.c

@@ -299,8 +299,7 @@ int journal_directory_vacuum(
                 n_list ++;
         }
 
-        if (n_list > 0)
-                qsort(list, n_list, sizeof(struct vacuum_info), vacuum_compare);
+        qsort_safe(list, n_list, sizeof(struct vacuum_info), vacuum_compare);
 
         for (i = 0; i < n_list; i++) {
                 struct statvfs ss;

src/journal/journalctl.c

@@ -761,7 +761,7 @@ static int get_relative_boot_id(sd_journal *j, sd_id128_t *boot_id, int relative
                 sd_journal_flush_matches(j);
         }
 
-        qsort(all_ids, count, sizeof(boot_id_t), boot_id_cmp);
+        qsort_safe(all_ids, count, sizeof(boot_id_t), boot_id_cmp);
 
         if (sd_id128_equal(*boot_id, SD_ID128_NULL)) {
                 if (relative > (int) count || relative <= -(int)count)

src/libsystemd-bus/bus-match.c

@@ -768,7 +768,7 @@ int bus_match_parse(
         }
 
         /* Order the whole thing, so that we always generate the same tree */
-        qsort(components, n_components, sizeof(struct bus_match_component), match_component_compare);
+        qsort_safe(components, n_components, sizeof(struct bus_match_component), match_component_compare);
 
         /* Check for duplicates */
         for (i = 0; i+1 < n_components; i++)

src/libudev/libudev-enumerate.c

@@ -276,7 +276,7 @@ _public_ struct udev_list_entry *udev_enumerate_get_list_entry(struct udev_enume
                 size_t move_later_prefix = 0;
 
                 udev_list_cleanup(&udev_enumerate->devices_list);
-                qsort(udev_enumerate->devices, udev_enumerate->devices_cur, sizeof(struct syspath), syspath_cmp);
+                qsort_safe(udev_enumerate->devices, udev_enumerate->devices_cur, sizeof(struct syspath), syspath_cmp);
 
                 max = udev_enumerate->devices_cur;
                 for (i = 0; i < max; i++) {

src/nss-myhostname/netlink.c

@@ -197,7 +197,8 @@ finish:
                 return r;
         }
 
-        qsort(list, n_list, sizeof(struct address), address_compare);
+        if (n_list)
+                qsort(list, n_list, sizeof(struct address), address_compare);
 
         *_list = list;
         *_n_list = n_list;

src/readahead/readahead-collect.c

@@ -536,8 +536,7 @@ done:
                 HASHMAP_FOREACH_KEY(q, p, files, i)
                         pack_file(pack, p, on_btrfs);
         } else {
-                struct item *ordered, *j;
-                unsigned k, n;
+                unsigned n;
 
                 /* On rotating media, order things by the block
                  * numbers */
@@ -545,25 +544,31 @@ done:
                 log_debug("Ordering...");
 
                 n = hashmap_size(files);
-                if (!(ordered = new(struct item, n))) {
-                        r = log_oom();
-                        goto finish;
-                }
+                if (n) {
+                        _cleanup_free_ struct item *ordered;
+                        struct item *j;
+                        unsigned k;
 
-                j = ordered;
-                HASHMAP_FOREACH_KEY(q, p, files, i) {
-                        memcpy(j, q, sizeof(struct item));
-                        j++;
-                }
+                        ordered = new(struct item, n);
+                        if (!ordered) {
+                                r = log_oom();
+                                goto finish;
+                        }
 
-                assert(ordered + n == j);
+                        j = ordered;
+                        HASHMAP_FOREACH_KEY(q, p, files, i) {
+                                memcpy(j, q, sizeof(struct item));
+                                j++;
+                        }
 
-                qsort(ordered, n, sizeof(struct item), qsort_compare);
+                        assert(ordered + n == j);
 
-                for (k = 0; k < n; k++)
-                        pack_file(pack, ordered[k].path, on_btrfs);
+                        qsort(ordered, n, sizeof(struct item), qsort_compare);
 
-                free(ordered);
+                        for (k = 0; k < n; k++)
+                                pack_file(pack, ordered[k].path, on_btrfs);
+                } else
+                        log_warning("No pack files");
         }
 
         log_debug("Finalizing...");

src/shared/cgroup-show.c

@@ -44,6 +44,8 @@ static void show_pid_array(int pids[], unsigned n_pids, const char *prefix, unsi
         unsigned i, m, pid_width;
         pid_t biggest = 0;
 
+        assert(n_pids > 0);
+
         /* Filter duplicates */
         m = 0;
         for (i = 0; i < n_pids; i++) {

src/shared/conf-files.c

@@ -127,7 +127,7 @@ static int conf_files_list_strv_internal(char ***strv, const char *suffix, const
                 return -ENOMEM;
         }
 
-        qsort(files, hashmap_size(fh), sizeof(char *), base_cmp);
+        qsort_safe(files, hashmap_size(fh), sizeof(char *), base_cmp);
         *strv = files;
 
         hashmap_free(fh);

src/shared/efivars.c

@@ -384,8 +384,7 @@ int efi_get_boot_options(uint16_t **options) {
                 list[count ++] = id;
         }
 
-        if (list)
-                qsort(list, count, sizeof(uint16_t), cmp_uint16);
+        qsort_safe(list, count, sizeof(uint16_t), cmp_uint16);
 
         *options = list;
         return count;

src/shared/fileio.c

@@ -662,6 +662,7 @@ int get_status_field(const char *filename, const char *pattern, char **field) {
         int r;
 
         assert(filename);
+        assert(pattern);
         assert(field);
 
         r = read_full_file(filename, &status, NULL);

src/shared/util.h

@@ -772,3 +772,15 @@ bool id128_is_valid(const char *s) _pure_;
 void parse_user_at_host(char *arg, char **user, char **host);
 
 int split_pair(const char *s, const char *sep, char **l, char **r);
+
+/**
+ * Normal qsort requires base to be nonnull. Here were require
+ * that only if nmemb > 0.
+ */
+static inline void qsort_safe(void *base, size_t nmemb, size_t size,
+                              int (*compar)(const void *, const void *)) {
+        if (nmemb) {
+                assert(base);
+                qsort(base, nmemb, size, compar);
+        }
+}

src/systemctl/systemctl.c

@@ -471,7 +471,7 @@ static int list_units(DBusConnection *bus, char **args) {
         if (r < 0)
                 return r;
 
-        qsort(unit_infos, c, sizeof(struct unit_info), compare_unit_info);
+        qsort_safe(unit_infos, c, sizeof(struct unit_info), compare_unit_info);
 
         output_units_list(unit_infos, c);
 
@@ -733,8 +733,8 @@ static int list_sockets(DBusConnection *bus, char **args) {
                 listen = triggered = NULL; /* avoid cleanup */
         }
 
-        qsort(socket_infos, cs, sizeof(struct socket_info),
-              (__compar_fn_t) socket_info_compare);
+        qsort_safe(socket_infos, cs, sizeof(struct socket_info),
+                   (__compar_fn_t) socket_info_compare);
 
         output_sockets_list(socket_infos, cs);
 
@@ -1108,7 +1108,7 @@ static int list_dependencies_one(DBusConnection *bus, const char *name, int leve
         if (r < 0)
                 return r;
 
-        qsort(deps, strv_length(deps), sizeof (char*), list_dependencies_compare);
+        qsort_safe(deps, strv_length(deps), sizeof (char*), list_dependencies_compare);
 
         STRV_FOREACH(c, deps) {
                 if (strv_contains(u, *c)) {
@@ -3532,7 +3532,7 @@ static int show_all(const char* verb,
         if (r < 0)
                 return r;
 
-        qsort(unit_infos, c, sizeof(struct unit_info), compare_unit_info);
+        qsort_safe(unit_infos, c, sizeof(struct unit_info), compare_unit_info);
 
         for (u = unit_infos; u < unit_infos + c; u++) {
                 _cleanup_free_ char *p = NULL;