Assorted small changes to the locked pool manager

Cherry-picked from:
- bitcoin/bitcoin#9233
- bitcoin/bitcoin#10483
- bitcoin/bitcoin#10645
- bitcoin/bitcoin#10969
- bitcoin/bitcoin#11351

Co-authored-by: fsb4000 <fsb4000@yandex.ru>
Co-authored-by: practicalswift <practicalswift@users.noreply.github.com>
Co-authored-by: Dan Raviv <dan@soundradix.com>

src/bench/lockedpool.cpp

@@ -21,14 +21,14 @@ static void LockedPool(benchmark::State& state)
 
     std::vector<void*> addr;
     for (int x=0; x<ASIZE; ++x)
-        addr.push_back(0);
+        addr.push_back(nullptr);
     uint32_t s = 0x12345678;
     while (state.KeepRunning()) {
         for (int x=0; x<BITER; ++x) {
             int idx = s & (addr.size()-1);
             if (s & 0x80000000) {
                 b.free(addr[idx]);
-                addr[idx] = 0;
+                addr[idx] = nullptr;
             } else if(!addr[idx]) {
                 addr[idx] = b.alloc((s >> 16) & (MSIZE-1));
             }

src/support/lockedpool.cpp

@@ -32,7 +32,7 @@
 #include <iostream>
 #endif
 
-LockedPoolManager* LockedPoolManager::_instance = NULL;
+LockedPoolManager* LockedPoolManager::_instance = nullptr;
 std::once_flag LockedPoolManager::init_flag;
 
 /*******************************************************************************/
@@ -97,7 +97,7 @@ void* Arena::alloc(size_t size)
 
 void Arena::free(void *ptr)
 {
-    // Freeing the NULL pointer is OK.
+    // Freeing the nullptr pointer is OK.
     if (ptr == nullptr) {
         return;
     }

src/support/lockedpool.h

@@ -51,6 +51,9 @@ public:
     Arena(void *base, size_t size, size_t alignment);
     virtual ~Arena();
 
+    Arena(const Arena& other) = delete; // non construction-copyable
+    Arena& operator=(const Arena&) = delete; // non copyable
+
     /** Memory statistics. */
     struct Stats
     {
@@ -86,9 +89,6 @@ public:
      */
     bool addressInArena(void *ptr) const { return ptr >= base && ptr < end; }
 private:
-    Arena(const Arena& other) = delete; // non construction-copyable
-    Arena& operator=(const Arena&) = delete; // non copyable
-
     typedef std::multimap<size_t, char*> SizeToChunkSortedMap;
     /** Map to enable O(log(n)) best-fit allocation, as it's sorted by size */
     SizeToChunkSortedMap size_to_free_chunk;
@@ -118,7 +118,7 @@ private:
  * An arena manages a contiguous region of memory. The pool starts out with one arena
  * but can grow to multiple arenas if the need arises.
  *
- * Unlike a normal C heap, the administrative structures are seperate from the managed
+ * Unlike a normal C heap, the administrative structures are separate from the managed
  * memory. This has been done as the sizes and bases of objects are not in themselves sensitive
  * information, as to conserve precious locked memory. In some operating systems
  * the amount of memory that can be locked is small.
@@ -159,9 +159,12 @@ public:
      * If this callback is provided and returns false, the allocation fails (hard fail), if
      * it returns true the allocation proceeds, but it could warn.
      */
-    LockedPool(std::unique_ptr<LockedPageAllocator> allocator, LockingFailed_Callback lf_cb_in = 0);
+    explicit LockedPool(std::unique_ptr<LockedPageAllocator> allocator, LockingFailed_Callback lf_cb_in = nullptr);
     ~LockedPool();
 
+    LockedPool(const LockedPool& other) = delete; // non construction-copyable
+    LockedPool& operator=(const LockedPool&) = delete; // non copyable
+
     /** Allocate size bytes from this arena.
      * Returns pointer on success, or 0 if memory is full or
      * the application tried to allocate 0 bytes.
@@ -177,9 +180,6 @@ public:
     /** Get pool usage statistics */
     Stats stats() const;
 private:
-    LockedPool(const LockedPool& other) = delete; // non construction-copyable
-    LockedPool& operator=(const LockedPool&) = delete; // non copyable
-
     std::unique_ptr<LockedPageAllocator> allocator;
 
     /** Create an arena from locked pages */
@@ -226,7 +226,7 @@ public:
     }
 
 private:
-    LockedPoolManager(std::unique_ptr<LockedPageAllocator> allocator);
+    explicit LockedPoolManager(std::unique_ptr<LockedPageAllocator> allocator);
 
     /** Create a new LockedPoolManager specialized to the OS */
     static void CreateInstance();