Stop spurious clang shallow analysis null pointer errors

Avoid 4 null pointer errors under clang shallow analysis (the default when
building under Xcode) by using tor_assert() to prove that the pointers
aren't null. Resolves issue 13284 via minor code refactoring.

changes/issue13284-spurious-clang-shallow-analyze-errors

@@ -0,0 +1,3 @@
+  o Minor bugfixes:
+    - Avoid 4 null pointer errors under clang shallow analysis by using
+      tor_assert() to prove that the pointers aren't null. Fixes bug 13284.

src/or/dirserv.c

@@ -1395,6 +1395,8 @@ dirserv_compute_performance_thresholds(routerlist_t *rl,
       routerinfo_t *ri = node->ri;
       const char *id = node->identity;
       uint32_t bw_kb;
+      /* resolve spurious clang shallow analysis null pointer errors */
+      tor_assert(ri);
       node->is_exit = (!router_exit_policy_rejects_all(ri) &&
                        exit_policy_is_general_exit(ri->exit_policy));
       uptimes[n_active] = (uint32_t)real_uptime(ri, now);

src/or/dirvote.c

@@ -647,6 +647,8 @@ dirvote_compute_params(smartlist_t *votes, int method, int total_authorities)
       next_param = NULL;
     else
       next_param = smartlist_get(param_list, param_sl_idx+1);
+    /* resolve spurious clang shallow analysis null pointer errors */
+    tor_assert(param);
     if (!next_param || strncmp(next_param, param, cur_param_len)) {
       /* We've reached the end of a series. */
       /* Make sure enough authorities voted on this param, unless the

src/or/routerlist.c

@@ -475,6 +475,8 @@ trusted_dirs_remove_old_certs(void)
         time_t cert_published;
         if (newest == cert)
           continue;
+        /* resolve spurious clang shallow analysis null pointer errors */
+        tor_assert(cert);
         expired = now > cert->expires;
         cert_published = cert->cache_info.published_on;
         /* Store expired certs for 48 hours after a newer arrives;