Schrober writes:
> Hi,
>
> I wondered why the container_of implementation is so complicated.
>
> #define container_of(ptr, type, member) ({ \
> const typeof( ((type *)0)->member ) *__mptr = (ptr); \
> (type *)( (char *)__mptr - offsetof(type,member) );})
>
> isn't the __mptr not unnecessary? Why not following version?
>
> #define container_of(ptr, type, member) \
> ((type *)((char *)(ptr) - offsetof(type, member)))
Compile-time type checking. The first version requires ptr to be
assignment-compatible with the type of the struct member, the second
version accepts random junk for ptr.
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