有人可以回答一下吗the vtable symbol may be undefined because the class is missing its key function

Build command failed.
Error while executing process D:\android_sdk\cmake\3.6.4111459\bin\cmake.exe with arguments {–build D:\cocos2d\chinesechess\proj.android\app.externalNativeBuild\cmake\debug\armeabi-v7a --target MyGame}
[1/1] Linking CXX shared library …\build\intermediates\cmake\debug\obj\armeabi-v7a\libMyGame.so
FAILED: cmd.exe /C “cd . && D:\android_sdk\ndk-bundle\toolchains\llvm\prebuilt\windows-x86_64\bin\clang++.exe --target=armv7-none-linux-androideabi16 --gcc-toolchain=D:/android_sdk/ndk-bundle/toolchains/arm-linux-androideabi-4.9/prebuilt/windows-x86_64 --sysroot=D:/android_sdk/ndk-bundle/sysroot -fPIC -isystem D:/android_sdk/ndk-bundle/sysroot/usr/include/arm-linux-androideabi -g -DANDROID -ffunction-sections -funwind-tables -fstack-protector-strong -no-canonical-prefixes -march=armv7-a -mfloat-abi=softfp -mfpu=vfpv3-d16 -mthumb -mfpu=neon -Wa,–noexecstack -Wformat -Werror=format-security -std=c++11 -frtti -fexceptions -fsigned-char -O0 -fno-limit-debug-info -Wl,–exclude-libs,libgcc.a -Wl,–exclude-libs,libatomic.a -nostdlib++ --sysroot D:/android_sdk/ndk-bundle/platforms/android-16/arch-arm -Wl,–build-id -Wl,–warn-shared-textrel -Wl,–fatal-warnings -Wl,–fix-cortex-a8 -Wl,–exclude-libs,libunwind.a -LD:/android_sdk/ndk-bundle/sources/cxx-stl/llvm-libc++/libs/armeabi-v7a -Wl,–no-undefined -Wl,-z,noexecstack -Qunused-arguments -Wl,-z,relro -Wl,-z,now -shared -Wl,-soname,libMyGame.so -o …\build\intermediates\cmake\debug\obj\armeabi-v7a\libMyGame.so CMakeFiles/MyGame.dir/Classes/AppDelegate.cpp.o CMakeFiles/MyGame.dir/Classes/StartScene.cpp.o CMakeFiles/MyGame.dir/proj.android/app/jni/hellocpp/main.cpp.o -Wl,–whole-archive engine/cocos/platform/libcpp_android_spec.a -Wl,–no-whole-archive lib/libcocos2d.a lib/libexternal.a …/…/…/…/…/…/cocos2d/external/Box2D/prebuilt/android/armeabi-v7a/libbox2d.a …/…/…/…/…/…/cocos2d/external/chipmunk/prebuilt/android/armeabi-v7a/libchipmunk.a …/…/…/…/…/…/cocos2d/external/freetype2/prebuilt/android/armeabi-v7a/libfreetype.a lib/libext_recast.a …/…/…/…/…/…/cocos2d/external/jpeg/prebuilt/android/armeabi-v7a/libjpeg.a …/…/…/…/…/…/cocos2d/external/webp/prebuilt/android/armeabi-v7a/libwebp.a …/…/…/…/…/…/cocos2d/external/bullet/prebuilt/android/armeabi-v7a/libLinearMath.a …/…/…/…/…/…/cocos2d/external/bullet/prebuilt/android/armeabi-v7a/libBulletDynamics.a …/…/…/…/…/…/cocos2d/external/bullet/prebuilt/android/armeabi-v7a/libBulletCollision.a …/…/…/…/…/…/cocos2d/external/bullet/prebuilt/android/armeabi-v7a/libLinearMath.a …/…/…/…/…/…/cocos2d/external/bullet/prebuilt/android/armeabi-v7a/libBulletMultiThreaded.a …/…/…/…/…/…/cocos2d/external/bullet/prebuilt/android/armeabi-v7a/libMiniCL.a …/…/…/…/…/…/cocos2d/external/tiff/prebuilt/android/armeabi-v7a/libtiff.a …/…/…/…/…/…/cocos2d/external/websockets/prebuilt/android/armeabi-v7a/libwebsockets.a …/…/…/…/…/…/cocos2d/external/uv/prebuilt/android/armeabi-v7a/libuv_a.a …/…/…/…/…/…/cocos2d/external/openssl/prebuilt/android/armeabi-v7a/libssl.a …/…/…/…/…/…/cocos2d/external/openssl/prebuilt/android/armeabi-v7a/libcrypto.a lib/libext_tinyxml2.a lib/libext_xxhash.a lib/libext_xxtea.a lib/libext_clipper.a lib/libext_edtaa3func.a lib/libext_convertUTF.a lib/libext_poly2tri.a lib/libext_md5.a …/…/…/…/…/…/cocos2d/external/curl/prebuilt/android/armeabi-v7a/libcurl.a …/…/…/…/…/…/cocos2d/external/png/prebuilt/android/armeabi-v7a/libpng.a engine/external/android-specific/cpufeatures/libext_cpufeatures.a -ldl lib/libext_pvmp3dec.a lib/libext_tremolo.a …/…/…/…/…/…/cocos2d/external/zlib/prebuilt/android/armeabi-v7a/libz.a lib/libext_unzip.a -lGLESv2 -lEGL -llog -landroid -lOpenSLES -latomic -lm “D:/android_sdk/ndk-bundle/sources/cxx-stl/llvm-libc++/libs/armeabi-v7a/libc++static.a” “D:/androidsdk/ndk-bundle/sources/cxx-stl/llvm-libc++/libs/armeabi-v7a/libc++abi.a” “D:/android_sdk/ndk-bundle/sources/cxx-stl/llvm-libc++/libs/armeabi-v7a/libandroid_support.a” “D:/android_sdk/ndk-bundle/sources/cxx-stl/llvm-libc++/libs/armeabi-v7a/libunwind.a” “-ldl” && cd .”
…/…/…/…/…/…/Classes/ChessBoard.hpp:0: error: undefined reference to ‘vtable for ChessBoard’
D:/android_sdk/ndk-bundle/toolchains/arm-linux-androideabi-4.9/prebuilt/windows-x86_64/lib/gcc/arm-linux-androideabi/4.9.x/…/…/…/…/arm-linux-androideabi/bin\ld: the vtable symbol may be undefined because the class is missing its key function
…/…/…/…/…/…/Classes/ChessM.hpp:0: error: undefined reference to ‘vtable for ChessM’
D:/android