From @usev6

The following code (from S06-advanced/wrap.t, test skipped for rakudo-j) dies on rakudo-jvm​:

$ perl6-j -e 'my @​t = gather { sub triangle { take "=" x 3; }; for reverse ^3 -> $n { &triangle.wrap({ take "=" x $n; callsame; take "=" x $n; }); }; triangle(); };'
control operator crossed continuation barrier
  in any call_with_capture at gen/jvm/Metamodel.nqp line 3843
  in block at -e line 1
  in block <unit> at -e line 1

I did a bisect and found that commit rakudo/rakudo@f3fe819621 broke it.

From @usev6

On Sat Apr 23 01​:51​:35 2016, bartolin@​gmx.de wrote​:

The following code (from S06-advanced/wrap.t, test skipped for rakudo-
j) dies on rakudo-jvm​:

$ perl6-j -e 'my @​t = gather { sub triangle { take "=" x 3; }; for
reverse ^3 -> $n { &triangle.wrap({ take "=" x $n; callsame; take "="
x $n; }); }; triangle(); };'
control operator crossed continuation barrier
in any call_with_capture at gen/jvm/Metamodel.nqp line 3843
in block at -e line 1
in block <unit> at -e line 1

I did a bisect and found that commit
rakudo/rakudo@f3fe819621 broke it.

Here is a golfed example​:

$ ./perl6-j -e 'gather { sub a { take "=" }; &a.wrap({ callsame }); a() }'
control operator crossed continuation barrier
  in any call_with_capture at gen/jvm/Metamodel.nqp line 3914
  in block at -e line 1
  in block <unit> at -e line 1

With the following change to nqp the code works as expected (and there are no new spectest failures)​:

====

diff --git a/src/vm/jvm/runtime/org/perl6/nqp/runtime/Ops.java b/src/vm/jvm/runtime/org/perl6/nqp/runtime/Ops.java
index fb95495..b0b4ba4 100644
--- a/src/vm/jvm/runtime/org/perl6/nqp/runtime/Ops.java
+++ b/src/vm/jvm/runtime/org/perl6/nqp/runtime/Ops.java
@@ -2386,8 +2386,6 @@ public final class Ops {
             ArgsExpectation.invokeByExpectation(tc, cr, csd, args);
         }
         catch (ControlException e) {
-            if (barrier && (e instanceof SaveStackException))
-                ExceptionHandling.dieInternal(tc, "control operator crossed continuation barrier");
             throw e;
         }
         catch (Throwable e) {

$ ./perl6-j -e 'say gather { sub a { take "=" }; &a.wrap({ callsame }); a() }'
(=)

My (wild) guess why the problem surfaced with commit f3fe819621 is this​: We use .pull-one now, that method uses 'nqp​::continuationreset' and the combination of that op, a control exception (from 'take') and 'callsame' leads to the SaveStackException.

From @usev6

I made a PR for my suggested change and with NQP commit 9da2705b1b the test passes on JVM.

I'm closing this ticket as 'resolved'.

@usev6 - Status changed from 'new' to 'resolved'