Could Linux explain spinlock.h then? Depending on which type you give to the PICK_OP macro, it performs a different operation. Its basically a C template. Seems a bit weird to complain about type context specific code and then use it in one of the most important parts of the kernel..

Here's the code: #define TYPE_EQUAL(lock, type) \ __builtin_types_compatible_p(typeof(lock), type )

#define PICK_OP(op, lock) \ do { \ if (TYPE_EQUAL((lock), raw_spinlock_t)) \ __spin##op((raw_spinlock_t )(lock)); \ else if (TYPE_EQUAL(lock, spinlock_t)) \ _spin##op((spinlock_t *)(lock)); \ else __bad_spinlock_type(); \ } while (0)