Let guard frames optionally pass through unwinding.

We have a bug in that when an exception occurs in a context
called from obj_print, the guard for stopping continuation
captures across obj_print also unintentially blocks the
unwinding. Let's make the unwinding blockage optional

* unwind.c (uw_unwind_to_exit_point): If a UW_GUARD is
encountered, do not abort if the uw_ok flag is set;
keep unwinding.
(uw_push_guard): New uw_ok argument, initializes the
uw_ok member of a guard frame.

* unwind.h (struct uw_guard): New struct type.
(union uw_frame): New member gu of type struct uw_guard.
(uw_push_guard): Declaration updated.

* ftw.c (ftw_callback): Pass zero as new uw_push_guard
argument: no unwinding across the POSIX library function ftw.

* glob.c (errfunc_thunk): Likewise, no unwinding across
the library function glob.

* lib.c (obj_print): Pass 1 as new uw_push_guard argument:
continuations can't be captured, but unwinding is okay.

1 files changed, 1 insertions, 1 deletions

diff --git a/lib.c b/lib.c
index fffe2970..f7b75809 100644
--- a/lib.c
+++ b/lib.c
@@ -9497,7 +9497,7 @@ val obj_print(val obj, val out, val pretty)
   struct strm_ctx *volatile ctx = ctx_orig, ctx_struct;
   uw_frame_t cont_guard;
 
-  uw_push_guard(&cont_guard);
+  uw_push_guard(&cont_guard, 1);
 
   uw_simple_catch_begin;