diff --git a/rts/Schedule.c b/rts/Schedule.c
index 4ddc94ba36aee65028271d243b78e42dc9837942..cf3eb328f46974b1c7e012e2a729ec1d710c67c6 100644
--- a/rts/Schedule.c
+++ b/rts/Schedule.c
@@ -2797,9 +2797,6 @@ exitScheduler (bool wait_foreign USED_IF_THREADS)
 
     shutdownCapabilities(task, wait_foreign);
 
-    // debugBelch("n_failed_trygrab_idles = %d, n_idle_caps = %d\n",
-    //            n_failed_trygrab_idles, n_idle_caps);
-
     exitMyTask();
 }
 
diff --git a/rts/Sparks.c b/rts/Sparks.c
index 3f8980485a710936143fb8dfeaa9128d08b30ad4..2b4bb22ab3eb220eac46d49a8f4c123d7b0f5fc0 100644
--- a/rts/Sparks.c
+++ b/rts/Sparks.c
@@ -119,11 +119,10 @@ pruneSparkQueue (bool nonmovingMarkFinished, Capability *cap)
 {
     SparkPool *pool;
     StgClosurePtr spark, tmp, *elements;
-    uint32_t n, pruned_sparks; // stats only
+    uint32_t pruned_sparks; // stats only
     StgInt botInd,oldBotInd,currInd; // indices in array (always < size)
     const StgInfoTable *info;
 
-    n = 0;
     pruned_sparks = 0;
 
     pool = cap->sparks;
@@ -217,7 +216,6 @@ pruneSparkQueue (bool nonmovingMarkFinished, Capability *cap)
               if (closure_SHOULD_SPARK(tmp)) {
                   elements[botInd] = tmp; // keep entry (new address)
                   botInd++;
-                  n++;
               } else {
                   pruned_sparks++; // discard spark
                   cap->spark_stats.fizzled++;
@@ -247,7 +245,6 @@ pruneSparkQueue (bool nonmovingMarkFinished, Capability *cap)
                   if (closure_SHOULD_SPARK(spark)) {
                       elements[botInd] = spark; // keep entry (new address)
                       botInd++;
-                      n++;
                   } else {
                       pruned_sparks++; // discard spark
                       cap->spark_stats.fizzled++;
@@ -265,7 +262,6 @@ pruneSparkQueue (bool nonmovingMarkFinished, Capability *cap)
                   // isAlive() also ignores static closures (see GCAux.c)
                   elements[botInd] = spark; // keep entry (new address)
                   botInd++;
-                  n++;
               } else {
                   pruned_sparks++; // discard spark
                   cap->spark_stats.fizzled++;
diff --git a/rts/TraverseHeap.c b/rts/TraverseHeap.c
index 027f99ebe0613aa508aa94b2dcb6898c779008d0..6ef3204d44c9cf9cd3066ff6e33b8a81759201e6 100644
--- a/rts/TraverseHeap.c
+++ b/rts/TraverseHeap.c
@@ -48,7 +48,7 @@ static void debug(const char *s, ...)
     va_end(ap);
 }
 #else
-#define debug(...)
+static void debug(const char *s STG_UNUSED, ...) {}
 #endif
 
 // number of blocks allocated for one stack
diff --git a/rts/sm/NonMoving.c b/rts/sm/NonMoving.c
index 018d7d76d9c63704537bb44e9a95bb16b9027a09..31a1d22a16c0dc42d06df488d1ff651fb2a3f13e 100644
--- a/rts/sm/NonMoving.c
+++ b/rts/sm/NonMoving.c
@@ -901,14 +901,12 @@ static void nonmovingMark_(MarkQueue *mark_queue, StgWeak **dead_weaks, StgTSO *
     // updated their snapshot pointers and move them to the sweep list.
     for (int alloca_idx = 0; alloca_idx < NONMOVING_ALLOCA_CNT; ++alloca_idx) {
         struct NonmovingSegment *filled = nonmovingHeap.allocators[alloca_idx].saved_filled;
-        uint32_t n_filled = 0;
         if (filled) {
             struct NonmovingSegment *seg = filled;
             while (true) {
                 // Set snapshot
                 nonmovingSegmentInfo(seg)->next_free_snap = seg->next_free;
                 SET_SEGMENT_STATE(seg, FILLED_SWEEPING);
-                n_filled++;
                 if (seg->link) {
                     seg = seg->link;
                 } else {
@@ -1161,24 +1159,20 @@ void assert_in_nonmoving_heap(StgPtr p)
         }
 
         // Search active segments
-        int seg_idx = 0;
         struct NonmovingSegment *seg = alloca->active;
         while (seg) {
             if (p >= (P_)seg && p < (((P_)seg) + NONMOVING_SEGMENT_SIZE_W)) {
                 return;
             }
-            seg_idx++;
             seg = seg->link;
         }
 
         // Search filled segments
-        seg_idx = 0;
         seg = alloca->filled;
         while (seg) {
             if (p >= (P_)seg && p < (((P_)seg) + NONMOVING_SEGMENT_SIZE_W)) {
                 return;
             }
-            seg_idx++;
             seg = seg->link;
         }
     }
diff --git a/rts/sm/NonMovingMark.c b/rts/sm/NonMovingMark.c
index 6ca963ec1de8916c024ab9264aca4606a8309f9c..87dc4112f68bab099a2e659abd56d8d445ff7f2b 100644
--- a/rts/sm/NonMovingMark.c
+++ b/rts/sm/NonMovingMark.c
@@ -268,7 +268,7 @@ void nonmovingMarkInit(void) {
 #endif
 }
 
-#if defined(THREADED_RTS) && defined(DEBUG)
+#if defined(THREADED_RTS)
 static uint32_t markQueueLength(MarkQueue *q);
 #endif
 static void init_mark_queue_(MarkQueue *queue);
@@ -985,7 +985,7 @@ void freeMarkQueue (MarkQueue *queue)
     freeChain_lock(queue->blocks);
 }
 
-#if defined(THREADED_RTS) && defined(DEBUG)
+#if defined(THREADED_RTS)
 static uint32_t
 markQueueLength (MarkQueue *q)
 {