sahlot arvind wrote:
> Recently I started looking into linux kernel and trying to understand the
> code.
> I am working with linux-2.6.9.
> in file include/llinux/list.h - I found something like this.
>
> #define INIT_LIST_HEAD(ptr) do { \
> (ptr)->next = (ptr); (ptr)->prev = (ptr); \
> } while (0)
>
>
> My question is why do we use a loop when we actually know that it is not
> going to execute more than once? Cannot we simply do -
>
> #define INIT_LIST_HEAD(ptr) {(ptr)->next = (ptr); (ptr)->prev = (ptr)}
>
> Do we get some kind of optimization by using while (0)?
>
with #define INIT_LIST_HEAD(ptr) {(ptr)->next = (ptr); (ptr)->prev = (ptr);}
try this:
if (...)
INIT_LIST_HEAD(ptr);
else
...;
you will get compilation error:
error: expected expression before 'else'
see why? expand the macro:
if (...)
{
(ptr)->next = (ptr);
(ptr)->prev = (ptr);
}; <---here
else
...;
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