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Walk the stack to determine extent of partial continuation

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* libguile/control.c (reify_partial_continuation): Walk the stack to
  determine the bottom of the captured stack.
This commit is contained in:
Andy Wingo 2013-10-23 17:18:24 +02:00
parent 186b56c4dc
commit 88e5caded5
1 changed files with 13 additions and 6 deletions
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19
libguile/control.c
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@ -86,6 +86,7 @@ reify_partial_continuation (SCM vm,
{ {
SCM vm_cont; SCM vm_cont;
scm_t_uint32 flags; scm_t_uint32 flags;
SCM *bottom_fp;
flags = SCM_F_VM_CONT_PARTIAL; flags = SCM_F_VM_CONT_PARTIAL;
/* If we are aborting to a prompt that has the same registers as those /* If we are aborting to a prompt that has the same registers as those
@ -95,15 +96,21 @@ reify_partial_continuation (SCM vm,
if (saved_registers && saved_registers == current_registers) if (saved_registers && saved_registers == current_registers)
flags |= SCM_F_VM_CONT_REWINDABLE; flags |= SCM_F_VM_CONT_REWINDABLE;
/* Since non-escape continuations should begin with a thunk application, the /* Walk the stack down until we find the first frame after saved_fp.
first bit of the stack should be a frame, with the saved fp equal to the fp We will save the stack down to that frame. It used to be that we
that was current when the prompt was made. */ could determine the stack bottom in O(1) time, but that's no longer
if ((SCM*)SCM_UNPACK (saved_sp[1]) != saved_fp) the case, since the thunk application doesn't occur where the
abort (); prompt is saved. */
for (bottom_fp = SCM_VM_DATA (vm)->fp;
SCM_FRAME_DYNAMIC_LINK (bottom_fp) > saved_fp;
bottom_fp = SCM_FRAME_DYNAMIC_LINK (bottom_fp));
if (SCM_FRAME_DYNAMIC_LINK (bottom_fp) != saved_fp)
abort();
/* Capture from the top of the thunk application frame up to the end. Set an /* Capture from the top of the thunk application frame up to the end. Set an
MVRA only, as the post-abort code is in an MV context. */ MVRA only, as the post-abort code is in an MV context. */
vm_cont = scm_i_vm_capture_stack (saved_sp + 4, vm_cont = scm_i_vm_capture_stack (bottom_fp - 1,
SCM_VM_DATA (vm)->fp, SCM_VM_DATA (vm)->fp,
SCM_VM_DATA (vm)->sp, SCM_VM_DATA (vm)->sp,
NULL, NULL,