Add a macro to count the number of args to a macro
Usage:
assert(MACRO_NR_ARGS() == 0);
or:
#define foo(...) printk("Got %d\n", MACRO_NR_ARGS(__VA_ARGS__))
Signed-off-by: Barret Rhoden <brho@cs.berkeley.edu>
diff --git a/kern/include/compiler.h b/kern/include/compiler.h
index 5159f24..df10b87 100644
--- a/kern/include/compiler.h
+++ b/kern/include/compiler.h
@@ -19,3 +19,10 @@
* nothing or to some attribute. We use it for the name of the pcpu variables
* .section, so need it to not be #defined yet. */
#undef __percpu
+
+/* If __VA_ARGS__ is empty, the ## will eat the comma to the left, so we call
+ * __MACRO_NARG with 1 + NR_ARGS arguments, then the 6, 5, 4, etc. __MACRO_NARG
+ * will strip the 0 (the _0), then the args (if any), and then return the Nth
+ * integer passed in, which will be the number of original args. */
+#define __MACRO_NARG(_0, _1, _2, _3, _4, _5, _6, x, ...) x
+#define MACRO_NR_ARGS(...) __MACRO_NARG(0, ##__VA_ARGS__, 6, 5, 4, 3, 2, 1, 0)
