Minor code tidying.

Author: mjp41

src/ds/helpers.h

@@ -56,7 +56,7 @@ namespace snmalloc
       length == bits::next_pow2_const(length), "Must be a power of two.");
 
   private:
-    T value;
+    T value = 0;
 
   public:
     operator T()

src/mem/largealloc.h

@@ -80,7 +80,7 @@ namespace snmalloc
      */
     std::atomic<uint64_t> last_low_memory_epoch = 0;
     std::atomic_flag lazy_decommit_guard;
-    void lazy_decommit()
+    SNMALLOC_SLOW_PATH void lazy_decommit()
     {
       // If another thread is try to do lazy decommit, let it continue.  If
       // we try to parallelise this, we'll most likely end up waiting on the
@@ -93,6 +93,7 @@ namespace snmalloc
       // the memory that we can.  Start with the small size classes so that we
       // hit cached superslabs first.
       // FIXME: We probably shouldn't do this all at once.
+      // FIXME: We currently Decommit all the sizeclasses larger than 0.
       for (size_t large_class = 0; large_class < NUM_LARGE_CLASSES;
            large_class++)
       {
@@ -327,7 +328,8 @@ namespace snmalloc
     void* alloc(size_t large_class, size_t size)
     {
       size_t rsize = bits::one_at_bit(SUPERSLAB_BITS) << large_class;
-      if (size == 0)
+      // For superslab size, we always commit the whole range.
+      if (large_class == 0)
         size = rsize;
 
       void* p = memory_provider.large_stack[large_class].pop();
@@ -407,7 +409,7 @@ namespace snmalloc
         size_t rsize = bits::one_at_bit(SUPERSLAB_BITS) << large_class;
 
         memory_provider.notify_not_using(
-          pointer_offset(p, OS_PAGE_SIZE), rsize - OS_PAGE_SIZE);
+        pointer_offset(p, OS_PAGE_SIZE), rsize - OS_PAGE_SIZE);
       }
 
       stats.superslab_push();

src/mem/metaslab.h

@@ -36,7 +36,7 @@ namespace snmalloc
      *  The list will be (allocated - needed - 1) long. The -1 is
      *  for the `link` element which is not in the free list.
      */
-    void* head;
+    void* head = nullptr;
 
     /**
      *  How many entries are not in the free list of slab, i.e.
@@ -51,7 +51,7 @@ namespace snmalloc
     /**
      *  How many entries have been allocated from this slab.
      */
-    uint16_t allocated;
+    uint16_t allocated = 0;
 
     // When a slab has free space it will be on the has space list for
     // that size class.  We use an empty block in this slab to be the

src/mem/superslab.h

@@ -84,7 +84,7 @@ namespace snmalloc
       {
         if (kind != Fresh)
         {
-          // If this wasn't previously Fresh, we need to zero some things.
+        // If this wasn't previously Fresh, we need to zero some things.
           used = 0;
           for (size_t i = 0; i < SLAB_COUNT; i++)
           {
@@ -97,21 +97,21 @@ namespace snmalloc
         kind = Super;
         // Point head at the first non-short slab.
         head = 1;
+      }
 
 #ifndef NDEBUG
-        auto curr = head;
-        for (size_t i = 0; i < SLAB_COUNT - used - 1; i++)
-        {
-          curr = (curr + meta[curr].next + 1) & (SLAB_COUNT - 1);
-        }
-        assert(curr == 0);
+      auto curr = head;
+      for (size_t i = 0; i < SLAB_COUNT - used - 1; i++)
+      {
+        curr = (curr + meta[curr].next + 1) & (SLAB_COUNT - 1);
+      }
+      if (curr != 0) abort();
 
-        for (size_t i = 0; i < SLAB_COUNT; i++)
-        {
-          assert(meta[i].is_unused());
-        }
-#endif
+      for (size_t i = 0; i < SLAB_COUNT; i++)
+      {
+        assert(meta[i].is_unused());
       }
+#endif
     }
 
     bool is_empty()
@@ -165,7 +165,7 @@ namespace snmalloc
       meta[0].link = get_initial_offset(sizeclass, true);
 
       used++;
-      return (Slab*)this;
+      return reinterpret_cast<Slab*>(this);
     }
 
     Slab* alloc_slab(sizeclass_t sizeclass)