tail recursive delegates

[BCS]

Reply to kzed at port70.net,

> Hello,
> so I wanted to test whether tail recursion optimization worked with
> delegates... And apparently I'm doing something wrong :) (Simple tail
> recursion with functions worked, as in gcc.)
> I'm using the GNU compiler; -O2 turns on tail recursion opt as with
> gcc.
> Can someone help?
> I'll paste my test procedure.
> 
> Thanks,
> Mate
> test.d:
> ----
> int delegate(int, int) counter(int by)
> {
> int cntr(int i, int acc) {
> printf("cntr i=%d acc=%d by=%d\n", i, acc, by);
> if(i < 1) return acc;
> return cntr(i - 1, acc += by);
> }
> return &cntr;
> }
> int main()
> {
> int delegate(int, int) count = counter(3);
> printf("%d", count(10, 0));
> return 0;
> }


'by' is a stack frame variable of counter and is invalid after counter returns. 
D 1.0 doesn't have full closures. The first case just happens to work because 
is some how doesn't stomp on the old stack frame. The second case changes 
something and then does stomp on stuff.


 int delegate(int, int) counter(int by)
 {
  struct Ret
  {
  int by;
  int cntr(int i, int acc) {
    printf("cntr i=%d acc=%d by=%d\n", i, acc, by);
    if(i < 1) return acc;
    return cntr(i - 1, acc += by);
   }
  auto ret = new Ret;
  ret.by=by;
  return &ret.cntr;
 }

that should work.

> ---
> eris ~% gdc -o test test.d
> eris ~% ./test
> cntr i=10 acc=0 by=3
> cntr i=9 acc=3 by=3
> cntr i=8 acc=6 by=3
> cntr i=7 acc=9 by=3
> cntr i=6 acc=12 by=3
> cntr i=5 acc=15 by=3
> cntr i=4 acc=18 by=3
> cntr i=3 acc=21 by=3
> cntr i=2 acc=24 by=3
> cntr i=1 acc=27 by=3
> cntr i=0 acc=30 by=3
> 30
> eris ~% gdc -o test test.d  -O2
> eris ~% ./test
> cntr i=10 acc=0 by=6530176
> cntr i=9 acc=6530176 by=6530176
> cntr i=8 acc=13060352 by=6530176
> cntr i=7 acc=19590528 by=6530176
> cntr i=6 acc=26120704 by=6530176
> cntr i=5 acc=32650880 by=6530176
> cntr i=4 acc=39181056 by=6530176
> cntr i=3 acc=45711232 by=6530176
> cntr i=2 acc=52241408 by=6530176
> cntr i=1 acc=58771584 by=6530176
> cntr i=0 acc=65301760 by=6530176
> 65301760