Assert that memory held by rephist is freed

The internal memory allocation and history object counters of the
reputation code can be used to verify the correctness of (part of) the
code. Using these counters revealed an issue where the memory allocation
counter is not decreased when the bandwidth arrays are freed.

A new function ensures the memory allocation counter is decreased when a
bandwidth array is freed.

This commit also removes an unnecessary cast which was found while
working on the code.

changes/bug17753

@@ -0,0 +1,4 @@
+  o Minor bugfixes (code correctness)
+    - Assert that allocated memory held by the reputation code is freed
+      according to its internal counters. Fixes bug 17753; bugfix on
+      tor-0.1.1.1-alpha.

src/or/rephist.c

@@ -148,7 +148,7 @@ get_link_history(const char *from_id, const char *to_id)
     return NULL;
   if (tor_digest_is_zero(to_id))
     return NULL;
-  lhist = (link_history_t*) digestmap_get(orhist->link_history_map, to_id);
+  lhist = digestmap_get(orhist->link_history_map, to_id);
   if (!lhist) {
     lhist = tor_malloc_zero(sizeof(link_history_t));
     rephist_total_alloc += sizeof(link_history_t);
@@ -1250,6 +1250,18 @@ bw_array_new(void)
   return b;
 }
 
+/** Free storage held by bandwidth array <b>b</b>. */
+static void
+bw_array_free(bw_array_t *b)
+{
+  if (!b) {
+    return;
+  }
+
+  rephist_total_alloc -= sizeof(bw_array_t);
+  tor_free(b);
+}
+
 /** Recent history of bandwidth observations for read operations. */
 static bw_array_t *read_array = NULL;
 /** Recent history of bandwidth observations for write operations. */
@@ -1266,10 +1278,11 @@ static bw_array_t *dir_write_array = NULL;
 static void
 bw_arrays_init(void)
 {
-  tor_free(read_array);
-  tor_free(write_array);
-  tor_free(dir_read_array);
-  tor_free(dir_write_array);
+  bw_array_free(read_array);
+  bw_array_free(write_array);
+  bw_array_free(dir_read_array);
+  bw_array_free(dir_write_array);
+
   read_array = bw_array_new();
   write_array = bw_array_new();
   dir_read_array = bw_array_new();
@@ -3172,10 +3185,19 @@ rep_hist_free_all(void)
 {
   hs_stats_free(hs_stats);
   digestmap_free(history_map, free_or_history);
-  tor_free(read_array);
-  tor_free(write_array);
-  tor_free(dir_read_array);
-  tor_free(dir_write_array);
+
+  bw_array_free(read_array);
+  read_array = NULL;
+
+  bw_array_free(write_array);
+  write_array = NULL;
+
+  bw_array_free(dir_read_array);
+  dir_read_array = NULL;
+
+  bw_array_free(dir_write_array);
+  dir_write_array = NULL;
+
   tor_free(exit_bytes_read);
   tor_free(exit_bytes_written);
   tor_free(exit_streams);
@@ -3190,5 +3212,8 @@ rep_hist_free_all(void)
   }
   rep_hist_desc_stats_term();
   total_descriptor_downloads = 0;
+
+  tor_assert(rephist_total_alloc == 0);
+  tor_assert(rephist_total_num == 0);
 }