Disabled MallocHooks code in Release due to performance concerns. Added enable_malloc_hooks flag to…

runtime/vm/malloc_hooks_test.cc

 // Copyright (c) 2017, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "platform/globals.h"
 
 #if defined(DART_USE_TCMALLOC) && !defined(PRODUCT)
 
 #include "platform/assert.h"
 #include "vm/class_finalizer.h"
 #include "vm/globals.h"
 #include "vm/malloc_hooks.h"
 #include "vm/symbols.h"
 #include "vm/unit_test.h"
 
 namespace dart {
 
 static void MallocHookTestBufferInitializer(volatile char* buffer,
                                             uintptr_t size) {
   // Run through the buffer and do something. If we don't do this and the memory
   // in buffer isn't touched, the tcmalloc hooks won't be called.
   for (uintptr_t i = 0; i < size; ++i) {
     buffer[i] = i;
   }
 }
 
 
 UNIT_TEST_CASE(BasicMallocHookTest) {
+  bool enable_malloc_hooks_saved = FLAG_enable_malloc_hooks;
+  FLAG_enable_malloc_hooks = true;
+
   MallocHooks::InitOnce();
   MallocHooks::ResetStats();
   EXPECT_EQ(0L, MallocHooks::allocation_count());
   EXPECT_EQ(0L, MallocHooks::heap_allocated_memory_in_bytes());
   const intptr_t buffer_size = 10;
   char* buffer = new char[buffer_size];
   MallocHookTestBufferInitializer(buffer, buffer_size);
 
   EXPECT_EQ(1L, MallocHooks::allocation_count());
   EXPECT_EQ(static_cast<intptr_t>(sizeof(char) * buffer_size),
             MallocHooks::heap_allocated_memory_in_bytes());
 
   delete[] buffer;
   EXPECT_EQ(0L, MallocHooks::allocation_count());
   EXPECT_EQ(0L, MallocHooks::heap_allocated_memory_in_bytes());
   MallocHooks::TearDown();
+
+  FLAG_enable_malloc_hooks = enable_malloc_hooks_saved;
 }
 
 
 UNIT_TEST_CASE(FreeUnseenMemoryMallocHookTest) {
+  bool enable_malloc_hooks_saved = FLAG_enable_malloc_hooks;
+  FLAG_enable_malloc_hooks = true;
+
   MallocHooks::InitOnce();
   const intptr_t pre_hook_buffer_size = 3;
   char* pre_hook_buffer = new char[pre_hook_buffer_size];
   MallocHookTestBufferInitializer(pre_hook_buffer, pre_hook_buffer_size);
 
   MallocHooks::ResetStats();
   EXPECT_EQ(0L, MallocHooks::allocation_count());
   EXPECT_EQ(0L, MallocHooks::heap_allocated_memory_in_bytes());
 
   const intptr_t buffer_size = 10;
   volatile char* buffer = new char[buffer_size];
   MallocHookTestBufferInitializer(buffer, buffer_size);
 
   EXPECT_EQ(1L, MallocHooks::allocation_count());
   EXPECT_EQ(static_cast<intptr_t>(sizeof(char) * buffer_size),
             MallocHooks::heap_allocated_memory_in_bytes());
 
   delete[] pre_hook_buffer;
   EXPECT_EQ(1L, MallocHooks::allocation_count());
   EXPECT_EQ(static_cast<intptr_t>(sizeof(char) * buffer_size),
             MallocHooks::heap_allocated_memory_in_bytes());
 
 
   delete[] buffer;
   EXPECT_EQ(0L, MallocHooks::allocation_count());
   EXPECT_EQ(0L, MallocHooks::heap_allocated_memory_in_bytes());
   MallocHooks::TearDown();
+
+  FLAG_enable_malloc_hooks = enable_malloc_hooks_saved;
 }
 
 };  // namespace dart
 
 #endif  // defined(DART_USE_TCMALLOC) && !defined(PRODUCT)