I can see that as an implementation detail, but it need not be one. There isn't a reason that a runtime couldn't use a flag value for absent args and let the c

I can see that as an implementation detail, but it need not be one. There isn't a reason that a runtime couldn't use a flag value for absent args and let the callee code set the value up on their side. I mean, the java runtime has all sorts of crazy stuff going on w/ a security manager, to almost zero benefit. Seems easy enough to make something like this work.