Add a comment explaining why initialize_allocate_handler() is not cal…

…led in the current library implementation

Signed-off-by: Dmitri Mokhov <[email protected]>

src/tbb/allocator.cpp

@@ -157,6 +157,14 @@ void initialize_cache_aligned_allocator() {
 }
 
 //! Executed on very first call through allocate_handler
+/** Only one of initialize_allocate_handler() and initialize_cache_aligned_allocate_handler()
+    is called, since each one of them also initializes the other.
+
+    In the current implementation of oneTBB library initialization, cache_aligned_allocate() is
+    used, which in turn calls initialize_cache_aligned_allocate_handler(). As mentioned above,
+    that also initializes the regular allocate_handler.
+
+    Therefore, initialize_allocate_handler() is not called in the current library implementation. */
 static void* initialize_allocate_handler(std::size_t size) {
     initialize_cache_aligned_allocator();
     __TBB_ASSERT(allocate_handler != &initialize_allocate_handler, nullptr);