cheng long wrote:
Hi,
Why can't we define the "container_of" as this?
#define container_of(ptr, type, member) \
( (type *)( (char *)ptr - offsetof(type,member) ) )
the line you dropped:
|
const typeof( ((type *)0)->member ) *__mptr = (ptr); |
gives the type-safety that makes this construct safe to use /
un-mis-usable / useful.
this line requires that the <type> actually has the member
*and* that the <ptr> is actually of that declared <type>
in Greg's words:
In order to do this kind of pointer manipulation, the code has to know
the type of pointer being passed to it. The driver core only passes in
the type of driver structure registered with it, so this type of
manipulation is safe. This also prevents other parts of the kernel from
modifying the unique fields of the structure used to control the
subsystem's code.
--
Kernelnewbies: Help each other learn about the Linux kernel.
Archive: http://mail.nl.linux.org/kernelnewbies/
FAQ: http://kernelnewbies.org/faq/
