From: Michał Lowas-Rzechonek <michal.lowas-rzechonek(a)silvair.com&gt; The macro is useful when e.g. scheduling timeouts, where l_timeout passed to l_timeout_notify_cb_t is a member of a larger object, and we would like to access this object while passing something else as user_data. --- ell/util.h | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/ell/util.h b/ell/util.h index c4ba7f8..95503de 100644 --- a/ell/util.h +++ b/ell/util.h @@ -35,6 +35,11 @@ extern "C" { #endif +#define l_container_of(ptr, type, member) ({ \ + const typeof( ((type *)0)->member ) *__mptr = (ptr); \ + (type *)( (char *)__mptr - offsetof(type,member) ); \ + }) + #define likely(x) __builtin_expect(!!(x), 1) #define unlikely(x) __builtin_expect(!!(x), 0) -- 2.19.1