Native engine memory leak detection system
- Usage steps

Native engine memory leak detection system

The native engine is developed using the C++ language, and memory leaks are inevitable. In order to facilitate game & engine developers to quickly find memory leaks, Cocos Creator 3.4.0 provides a memory leak detection system.

Compared with other memory leak detection tools, the built-in memory leak detection tool in Cocos Creator has the following advantages:

Cross-platform: support Windows/Android/Mac/iOS platforms.
Ease of use: no need to download additional tools and perform complex configurations. Support output of stack information at memory leaks, which is convenient for quickly locating leaks.
Consistency: the usage process of each platform is almost the same: start the game from the IDE -> run for a period of time -> close the game -> view the IDE output log.
Real-time: although the frame rate of the game in the profiling mode has dropped, it still maintains the real-time running frame rate.
Accuracy: theoretically zero false positives.

Usage steps

The memory leak detection system is disabled by default. To enable it, you need to modify the value of the macro USE_MEMORY_LEAK_DETECTOR in the engine-native/cocos/base/Config.h file of the engine directory to 1.
```
 #ifndef USE_MEMORY_LEAK_DETECTOR
     #define USE_MEMORY_LEAK_DETECTOR 1
 #endif
```
The Android platform requires one additional step as a result of the different implementation mechanisms amongst platforms:

Add a line of code set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -finstrument-functions") to the native/engine/android/CMakeLists.txt file in the project directory, as follows:
```
 set(PROJ_SOURCES
     ${CMAKE_CURRENT_LIST_DIR}/../common/Classes/Game.h
     ${CMAKE_CURRENT_LIST_DIR}/../common/Classes/Game.cpp
     ${CMAKE_CURRENT_LIST_DIR}/jni/main.cpp
 )
 set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -finstrument-functions")
```
Start the game from the IDE corresponding to the native platform (such as Visual Studio, Android Studio, Xcode), and close the game after running for a period of time. If there is any memory leak, the detailed information of the memory leak will be output in the output window of the IDE at this time.
- Windows platform
  
  In the Release version, if more friendly stack information is needed, right-click the executable project-properties, open the project properties page, and make the following settings:
  - Linker -> Debugging -> Generate Debug Info: Generate Debug Information(/DEBUG)
  - C/C++ -> Optimization -> Optimization: Disabled(/Od)\
  - C/C++ -> Optimization -> Inline Function Expansion：Disabled(/Ob0)
- Android platform
- Mac/iOS platform
Fix the leak according to the information output by the Native platform IDE, and repeat until there is no leak.