container_of

[Anish Kumar]

> On Jan 17, 2015, at 8:32 AM, Simon Brand <simon.brand at postadigitale.de> wrote:
> 
> Good evening,
> 
> i read the article about the container_of function:
> http://www.kroah.com/log/linux/container_of.html
> 
> I understand what it does and how it works.
> 
> I thought, it could be simplified by replacing it through this:
> 
> #define container_of(ptr, type, member) ({ \
>                (type *)( (char *)ptr - offsetof(type,member) );})
> 
> Original:
> #define container_of(ptr, type, member) ({ \
>                const typeof( ((type *)0)->member ) *__mptr = (ptr); 
>                (type *)( (char *)__mptr - offsetof(type,member) );})
> 
> 
> ptr has the type of a pointer to the member, which should be the same
> as __mptr? The value should although be the same.
> 
> First I tried it in a self written script, then replaced it in
> include/linux/kernel.h and compiled it as usermode linux -> working
> well.
> 
> Then I compiled it and run it in a VM, but it is not working.
What do you mean by that? What is not working?
> 
> Can you please explain to me, why the original version is always working
> and "mine" is not? 
> 
> Thank you for your time!
> 
> Regards,
> Simon
> 
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