Re: Fwd: Question about container_of macro.

[Alan Stern <stern@xxxxxxxxxxxxxxxxxxx>]

On Thu, 17 Jan 2008, Manish Katiyar wrote:

> My question is instead of defining container_of as:
> 
> #define container_of(ptr, type, member) ({ \
>                 const typeof( ((type *)0)->member ) *__mptr = (ptr);
>                 (type *)( (char *)__mptr - offsetof(type,member) );})
> 
> 
> Why won't this simply work :
> 
> #define container_of(ptr, type, member) ({ \
>                         (type *)( (char *)(ptr) - offsetof(type,member) );})

Indeed, or even this:

#define container_of(ptr, type, member) \
			((type *) ((char *)(ptr) - offsetof(type,member)))

Alan Stern


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