Question with "container_of(ptr, type, member)"

I have a question about the macro " container_of(ptr, type, member) " I can write it as this,

  #define container_of(ptr, type, member) ({ \
	(type *) ((char *) ptr - offset_of(type, member)); \
	})
It can act the same as
#define container_of(ptr, type, member) ({            \
	 const typeof( ((type *)0)->member ) *__mptr = (ptr);    \
	 (type *)( (char *)__mptr - offsetof(type,member) );})

So why we don't use the first one ?
Thanks for your answer.
(I am a kernel newbie ,and sorry for my poor english~)

Quoted 9 lines · peter

I have a question about the macro " container_of(ptr, type, member) " I can write it as this,

  #define container_of(ptr, type, member) ({ \
	(type *) ((char *) ptr - offset_of(type, member)); \
	})
It can act the same as
#define container_of(ptr, type, member) ({            \
	 const typeof( ((type *)0)->member ) *__mptr = (ptr);    \
	 (type *)( (char *)__mptr - offsetof(type,member) );})

Quoted 3 lines

So why we don't use the first one ?
Thanks for your answer.
(I am a kernel newbie ,and sorry for my poor english~)

The version used by the Linux kernel does type checking.

~Ryan