xcode 9 irrlicht engine build error: unknown type name 'u32'

Question

I use irrlicht engine for my ios game, everything works fine before xcode 9. But after I update my xcode to 9th version, when I compile my engine, xcode shows many buildtime errors, mainly are the unknown type name 'u32' error and which typedef in 'types.h' of the engine. Here is some of the source code in the types.h:

    namespace irrlicht
    {

     /** These are typedef for basic types, it ensures portability of the engine. */

    typedef unsigned char   u8;         //! 8 bit unsigned variable.
    typedef signed char     s8;         //! 8 bit signed variable.
    typedef char            c8;         //! 8 bit character variable.

    typedef unsigned short  u16;        //! 16 bit unsigned variable.
    typedef signed short    s16;        //! 16 bit signed variable.

    typedef unsigned int  u32;//! 32 bit unsigned variable.

    typedef signed int      s32;        //! 32 bit signed variable.
    typedef float           f32;        //! 32 bit floating point variable.
    ...

anyone knows how to fix this? Many thanks!