It is wrong to compile box2d on Mac.

[liudb5]

cd box2d && CXXFLAGS=" -isysroot /Applications/Xcode.app/Contents/Developer/Platforms/iPhoneOS.platform/Developer/SDKs/iPhoneOS11.4.sdk -arch armv7 -miphoneos-version-min=6.0 -mcpu=cortex-a8 -I/Users/liudb/GitHub/cocos2d-x-3rd-party-libs-src/contrib/install-ios/armv7/include -O3 -DNDEBUG -std=c++11" CFLAGS=" -isysroot /Applications/Xcode.app/Contents/Developer/Platforms/iPhoneOS.platform/Developer/SDKs/iPhoneOS11.4.sdk -arch armv7 -miphoneos-version-min=6.0 -mcpu=cortex-a8 -I/Users/liudb/GitHub/cocos2d-x-3rd-party-libs-src/contrib/install-ios/armv7/include -O3 -DNDEBUG " cmake . -DCMAKE_TOOLCHAIN_FILE=/Users/liudb/GitHub/cocos2d-x-3rd-party-libs-src/contrib/ios-armv7/toolchain.cmake -DCMAKE_INSTALL_PREFIX=/Users/liudb/GitHub/cocos2d-x-3rd-party-libs-src/contrib/install-ios/armv7
-- Configuring done
-- Generating done
-- Build files have been written to: /Users/liudb/GitHub/cocos2d-x-3rd-party-libs-src/contrib/ios-armv7/box2d
cd box2d && /Applications/Xcode.app/Contents/Developer/usr/bin/make
[ 2%] Building CXX object CMakeFiles/box2d.dir/Box2D/Box2D/Collision/Shapes/b2ChainShape.cpp.o
In file included from /Users/liudb/GitHub/cocos2d-x-3rd-party-libs-src/contrib/ios-armv7/box2d/Box2D/Box2D/Collision/Shapes/b2ChainShape.cpp:19:
/Users/liudb/GitHub/cocos2d-x-3rd-party-libs-src/contrib/ios-armv7/box2d/Box2D/Box2D/Collision/Shapes/b2ChainShape.h:62:52: warning:
'override' keyword is a C++11 extension [-Wc++11-extensions]
b2Shape* Clone(b2BlockAllocator* allocator) const override;
^
/Users/liudb/GitHub/cocos2d-x-3rd-party-libs-src/contrib/ios-armv7/box2d/Box2D/Box2D/Collision/Shapes/b2ChainShape.h:65:30: warning:
'override' keyword is a C++11 extension [-Wc++11-extensions]
int32 GetChildCount() const override;
^
/Users/liudb/GitHub/cocos2d-x-3rd-party-libs-src/contrib/ios-armv7/box2d/Box2D/Box2D/Collision/Shapes/b2ChainShape.h:72:70: warning:
'override' keyword is a C++11 extension [-Wc++11-extensions]
bool TestPoint(const b2Transform& transform, const b2Vec2& p) const override;
^
/Users/liudb/GitHub/cocos2d-x-3rd-party-libs-src/contrib/ios-armv7/box2d/Box2D/Box2D/Collision/Shapes/b2ChainShape.h:76:60: warning:
'override' keyword is a C++11 extension [-Wc++11-extensions]
const b2Transform& transform, int32 childIndex) const override;
^
/Users/liudb/GitHub/cocos2d-x-3rd-party-libs-src/contrib/ios-armv7/box2d/Box2D/Box2D/Collision/Shapes/b2ChainShape.h:79:87: warning:
'override' keyword is a C++11 extension [-Wc++11-extensions]
void ComputeAABB(b2AABB* aabb, const b2Transform& transform, int32 childIndex) const override;
^
/Users/liudb/GitHub/cocos2d-x-3rd-party-libs-src/contrib/ios-armv7/box2d/Box2D/Box2D/Collision/Shapes/b2ChainShape.h:83:64: warning:
'override' keyword is a C++11 extension [-Wc++11-extensions]
void ComputeMass(b2MassData* massData, float32 density) const override;
^
/Users/liudb/GitHub/cocos2d-x-3rd-party-libs-src/contrib/ios-armv7/box2d/Box2D/Box2D/Collision/Shapes/b2ChainShape.h:99:15: error:
use of undeclared identifier 'nullptr'
m_vertices = nullptr;
^
In file included from /Users/liudb/GitHub/cocos2d-x-3rd-party-libs-src/contrib/ios-armv7/box2d/Box2D/Box2D/Collision/Shapes/b2ChainShape.cpp:20:
/Users/liudb/GitHub/cocos2d-x-3rd-party-libs-src/contrib/ios-armv7/box2d/Box2D/Box2D/Collision/Shapes/b2EdgeShape.h:36:52: warning:
'override' keyword is a C++11 extension [-Wc++11-extensions]
b2Shape* Clone(b2BlockAllocator* allocator) const override;
^
/Users/liudb/GitHub/cocos2d-x-3rd-party-libs-src/contrib/ios-armv7/box2d/Box2D/Box2D/Collision/Shapes/b2EdgeShape.h:39:30: warning:
'override' keyword is a C++11 extension [-Wc++11-extensions]
int32 GetChildCount() const override;
^
/Users/liudb/GitHub/cocos2d-x-3rd-party-libs-src/contrib/ios-armv7/box2d/Box2D/Box2D/Collision/Shapes/b2EdgeShape.h:42:70: warning:
'override' keyword is a C++11 extension [-Wc++11-extensions]
bool TestPoint(const b2Transform& transform, const b2Vec2& p) const override;
^
/Users/liudb/GitHub/cocos2d-x-3rd-party-libs-src/contrib/ios-armv7/box2d/Box2D/Box2D/Collision/Shapes/b2EdgeShape.h:46:59: warning:
'override' keyword is a C++11 extension [-Wc++11-extensions]
const b2Transform& transform, int32 childIndex) const override;
^
/Users/liudb/GitHub/cocos2d-x-3rd-party-libs-src/contrib/ios-armv7/box2d/Box2D/Box2D/Collision/Shapes/b2EdgeShape.h:49:87: warning:
'override' keyword is a C++11 extension [-Wc++11-extensions]
void ComputeAABB(b2AABB* aabb, const b2Transform& transform, int32 childIndex) const override;
^
/Users/liudb/GitHub/cocos2d-x-3rd-party-libs-src/contrib/ios-armv7/box2d/Box2D/Box2D/Collision/Shapes/b2EdgeShape.h:52:64: warning:
'override' keyword is a C++11 extension [-Wc++11-extensions]
void ComputeMass(b2MassData* massData, float32 density) const override;
^
/Users/liudb/GitHub/cocos2d-x-3rd-party-libs-src/contrib/ios-armv7/box2d/Box2D/Box2D/Collision/Shapes/b2ChainShape.cpp:32:15: error:
use of undeclared identifier 'nullptr'
m_vertices = nullptr;
^
12 warnings and 2 errors generated.
make[3]: *** [CMakeFiles/box2d.dir/Box2D/Box2D/Collision/Shapes/b2ChainShape.cpp.o] Error 1
make[2]: *** [CMakeFiles/box2d.dir/all] Error 2
make[1]: *** [all] Error 2
make: *** [.box2d] Error 2