From that it looks like the caller always has to allocate the right amount of space on the stack to hold the result. What if the result size is known only by th

From that it looks like the caller always has to allocate the right amount of space on the stack to hold the result. What if the result size is known only by the callee? Denying yourself the use of the heap is also going to make closures rather difficult. You can use this style to pass back a function pointer, but the caller would also need to allocate space for the callee's captured variables. Ick.