gc: bug in sub-str on lazy string argument.

This showed up as an intermittent segfault on OpenBSD
of the test case tests/006/freeform-5.txr, reproducible
quite often, around 30% to 60%. This was with gcc 4.2.1.

* lib.c (lazy_sub_str): We need a gc_hint here on the
prefix hend in pfxcopy. The garbage collector is
scavenging that object, not seeing that we planted
it into a malloced structure.

1 files changed, 1 insertions, 0 deletions

diff --git a/lib.c b/lib.c
index b1ce9e9c..3a704997 100644
--- a/lib.c
+++ b/lib.c
@@ -5653,6 +5653,7 @@ static val lazy_sub_str(val lstr, val from, val to)
       lsub->ls.props = coerce(struct lazy_string_props *,
                               chk_copy_obj(coerce(mem_t *, lstr->ls.props),
                                            sizeof *lstr->ls.props));
+      gc_hint(pfxcopy);
       return lsub;
     }
   }