Kernel's “container_of” - any way to make it ISO conforming?

Question

While looking at Linux kernel\'s implementation of doubly linked circular lists, I\'ve found following macro:

#define container_of(ptr, type, member) ({              


        

Answer 1

The macro is written the way it is to perfom a type check on ptr. It's possible to use a compound literal instead of the statement expression and fall back to a simple check for pointers instead of using __typeof__ if the compiler is not gcc-compatible:

#ifdef __GNUC__
#define member_type(type, member) __typeof__ (((type *)0)->member)
#else
#define member_type(type, member) const void
#endif

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