Improve memory tracer

Fixed a bug and compiler warning in the memory tracer implementation.

Author: neilt6

hal/common/mbed_alloc_wrappers.cpp

@@ -46,15 +46,23 @@ typedef struct {
     uint32_t pad;
 } alloc_info_t;
 
-static SingletonPtr<PlatformMutex> malloc_stats_mutex;
+#ifdef MBED_MEM_TRACING_ENABLED
 static SingletonPtr<PlatformMutex> mem_trace_mutex;
+#endif
+#ifdef MBED_HEAP_STATS_ENABLED
+static SingletonPtr<PlatformMutex> malloc_stats_mutex;
 static mbed_stats_heap_t heap_stats = {0, 0, 0, 0, 0};
+#endif
 
 void mbed_stats_heap_get(mbed_stats_heap_t *stats)
 {
+#ifdef MBED_HEAP_STATS_ENABLED
     malloc_stats_mutex->lock();
     memcpy(stats, &heap_stats, sizeof(mbed_stats_heap_t));
     malloc_stats_mutex->unlock();
+#else
+    memset(stats, 0, sizeof(mbed_stats_heap_t));
+#endif
 }
 
 /******************************************************************************/
@@ -260,12 +268,12 @@ extern "C" void* $Sub$$realloc(void *ptr, size_t size) {
         free(ptr);
     }
 #else // #ifdef MBED_HEAP_STATS_ENABLED
-    mem_trace_mutex->lock();
     new_ptr = $Super$$realloc(ptr, size);
-    mem_trace_mutex->unlock();
 #endif // #ifdef MBED_HEAP_STATS_ENABLED
 #ifdef MBED_MEM_TRACING_ENABLED
+    mem_trace_mutex->lock();
     mbed_mem_trace_realloc(new_ptr, ptr, size, MBED_CALLER_ADDR());
+    mem_trace_mutex->unlock();
 #endif // #ifdef MBED_MEM_TRACING_ENABLED
     return new_ptr;
 }