VM code question

[Darren Williams]

I have a small question wrt some VM code.
source file is include/linux/kernel.h

#define container_of(ptr, type, member) ({                      \
        const typeof( ((type *)0)->member ) *__mptr = (ptr);    \
        (type *)( (char *)__mptr - offsetof(type,member) );})

what is the use of the 0 (zero) in the typeof? I am thinking
that we are casting 0 to (type *) then referencing 'member' of
'type', however why do we require the 0 ?

Just curious

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Darren Williams <dsw@xxxxxxxxxxxxxxxxxx>
Gelato@UNSW <www.gelato.unsw.edu.au>
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