include/linux/kernel.h: add typeof_member() macro

Add typeof_member() macro so that types can be extracted without
introducing dummy variables.

Link: http://lkml.kernel.org/r/20190529190720.GA5703@avx2Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

include/linux/kernel.h

@@ -88,6 +88,8 @@
  */
 #define FIELD_SIZEOF(t, f) (sizeof(((t*)0)->f))
 
+#define typeof_member(T, m)	typeof(((T*)0)->m)
+
 #define DIV_ROUND_UP __KERNEL_DIV_ROUND_UP
 
 #define DIV_ROUND_DOWN_ULL(ll, d) \