Add suspendable-continuation?

* doc/ref/api-control.texi (Prompt Primitives): Document
  suspendable-continuation?.
* libguile/control.c (scm_suspendable_continuation_p): New procedure.
  (scm_init_ice_9_control): New extension procedure, defines
  suspendable-continuation?.
  (scm_init_control): Register scm_init_ice_9_control.
* libguile/eval.c (eval):
* libguile/throw.c (catch):
* libguile/continuations.c (scm_i_make_continuation): Restore resumable
  prompt cookie after continuation invocation.
* libguile/vm.c (scm_call_n): Arrange to set resumable_prompt_cookie
  during invocation of VM.
* libguile/vm.h (struct scm_vm): Add resumable_prompt_cookie member.
* module/ice-9/control.scm: Export suspendable-continuation?.
* test-suite/tests/control.test ("suspendable-continuation?"): New
  test.

1 files changed, 1 insertions, 0 deletions

diff --git a/libguile/vm.h b/libguile/vm.h
index 2ca4f2ab4..b26f7f406 100644
--- a/libguile/vm.h
+++ b/libguile/vm.h
@@ -47,6 +47,7 @@ struct scm_vm {
   union scm_vm_stack_element *stack_top; /* highest address in allocated stack */
   SCM overflow_handler_stack;   /* alist of max-stack-size -> thunk */
   SCM hooks[SCM_VM_NUM_HOOKS];	/* hooks */
+  const void *resumable_prompt_cookie; /* opaque cookie */
   int engine;                   /* which vm engine we're using */
 };