Attached is a patch that should improve weak vectors and prevent
`vector-ref' from segfaulting on them after a GC.
The root of the problem was that weak vectors were being allocated as
containing no pointers *and* disappearing links were not being
registered for initial elements. If you, however, created an empty weak
vector and then `vector-set!' the elements things were fine.
I'm not sure that weak vectors should have their allocated memory marked
as containing no pointers, but it seems to work so I left that alone in
case there was some magic going on that I didn't quite grok.
CC any replies to me; I'm not subscribed to bug-guile.
>From a20475f1f9643093ea96118a71826623ecf15220 Mon Sep 17 00:00:00 2001
From: Clinton Ebadi <clin...@unknownlamer.org>
Date: Thu, 1 Apr 2010 13:11:10 -0400
Subject: [PATCH] Fix weak vectors
* libguile/vectors.c (scm_i_make_weak_vector,
scm_i_make_weak_vector_from_list): Register elements as disappearing links.
* libguile/vectors.c (do_weak_vector_ref): New function to access an
element of a weak vector while the allocator lock is held.
* libguile/vectors.c (scm_c_vector_ref): Use `do_weak_vector_ref' when
accessing weak vectors.
* libguile/vectors.c (scm_c_vector_set_x): Deregister link before
registering disappearing link to new object. Might not be needed.
* libguile/vectors.c (scm_c_vector_ref, scm_c_vector_set_x): Only
check for NULLified pointers in weak vectors and not in weak hash
vectors (the elements of a WHVEC are not weak).
---
libguile/vectors.c | 66 ++++++++++++++++++++++++++++++++++++++-------------
1 files changed, 49 insertions(+), 17 deletions(-)
diff --git a/libguile/vectors.c b/libguile/vectors.c
index 6ac5acb..f72c927 100644
--- a/libguile/vectors.c
+++ b/libguile/vectors.c
@@ -203,22 +203,46 @@ scm_vector_ref (SCM v, SCM k)
}
#undef FUNC_NAME
+struct t_weak_vector_ref_args
+{
+ SCM vector;
+ size_t k;
+};
+
+/* Accessing weak pointers *must* be done with the allocator lock held */
+static void*
+do_weak_vector_ref (void* data)
+{
+ struct t_weak_vector_ref_args *args = (struct t_weak_vector_ref_args *) data;
+ register SCM elt = (SCM_I_VECTOR_ELTS(args->vector))[args->k];
+
+ if (elt == SCM_PACK (NULL))
+ /* ELT was a weak pointer and got nullified by the GC. */
+ return SCM_BOOL_F;
+
+ return elt;
+}
+
SCM
scm_c_vector_ref (SCM v, size_t k)
{
if (SCM_I_IS_VECTOR (v))
{
- register SCM elt;
-
if (k >= SCM_I_VECTOR_LENGTH (v))
scm_out_of_range (NULL, scm_from_size_t (k));
- elt = (SCM_I_VECTOR_ELTS(v))[k];
- if ((elt == SCM_PACK (NULL)) && SCM_I_WVECTP (v))
- /* ELT was a weak pointer and got nullified by the GC. */
- return SCM_BOOL_F;
+ if (SCM_I_WVECTP (v) && !SCM_IS_WHVEC (v))
+ {
+ struct t_weak_vector_ref_args args;
+ args.vector = v;
+ args.k = k;
- return elt;
+ return GC_call_with_alloc_lock (do_weak_vector_ref, &args);
+ }
+ else
+ {
+ return (SCM_I_VECTOR_ELTS(v))[k];
+ }
}
else if (SCM_I_ARRAYP (v) && SCM_I_ARRAY_NDIM (v) == 1)
{
@@ -226,18 +250,20 @@ scm_c_vector_ref (SCM v, size_t k)
SCM vv = SCM_I_ARRAY_V (v);
if (SCM_I_IS_VECTOR (vv))
{
- register SCM elt;
-
if (k >= dim->ubnd - dim->lbnd + 1)
scm_out_of_range (NULL, scm_from_size_t (k));
k = SCM_I_ARRAY_BASE (v) + k*dim->inc;
- elt = (SCM_I_VECTOR_ELTS (vv))[k];
- if ((elt == SCM_PACK (NULL)) && (SCM_I_WVECTP (vv)))
- /* ELT was a weak pointer and got nullified by the GC. */
- return SCM_BOOL_F;
+ if (SCM_I_WVECTP (vv) && !SCM_IS_WHVEC (vv))
+ {
+ struct t_weak_vector_ref_args args;
+ args.vector = vv;
+ args.k = k;
- return elt;
+ return GC_call_with_alloc_lock (do_weak_vector_ref, &args);
+ }
+
+ return (SCM_I_VECTOR_ELTS (vv))[k];
}
scm_wrong_type_arg_msg (NULL, 0, v, "non-uniform vector");
}
@@ -275,10 +301,11 @@ scm_c_vector_set_x (SCM v, size_t k, SCM obj)
if (k >= SCM_I_VECTOR_LENGTH (v))
scm_out_of_range (NULL, scm_from_size_t (k));
(SCM_I_VECTOR_WELTS(v))[k] = obj;
- if (SCM_I_WVECTP (v))
+ if (SCM_I_WVECTP (v) && !SCM_IS_WHVEC (v))
{
/* Make it a weak pointer. */
GC_PTR link = (GC_PTR) & ((SCM_I_VECTOR_WELTS (v))[k]);
+ GC_unregister_disappearing_link (link);
SCM_I_REGISTER_DISAPPEARING_LINK (link, obj);
}
}
@@ -293,10 +320,11 @@ scm_c_vector_set_x (SCM v, size_t k, SCM obj)
k = SCM_I_ARRAY_BASE (v) + k*dim->inc;
(SCM_I_VECTOR_WELTS (vv))[k] = obj;
- if (SCM_I_WVECTP (vv))
+ if (SCM_I_WVECTP (vv) && !SCM_IS_WHVEC (vv))
{
/* Make it a weak pointer. */
GC_PTR link = (GC_PTR) & ((SCM_I_VECTOR_WELTS (vv))[k]);
+ GC_unregister_disappearing_link (link);
SCM_I_REGISTER_DISAPPEARING_LINK (link, obj);
}
}
@@ -421,7 +449,10 @@ scm_i_make_weak_vector (scm_t_bits type, SCM size, SCM fill)
base = SCM_I_WVECT_GC_WVELTS (wv);
for (j = 0; j != c_size; ++j)
- base[j] = fill;
+ {
+ base[j] = fill;
+ SCM_I_REGISTER_DISAPPEARING_LINK((GC_PTR) base + j, (GC_PTR) SCM_UNPACK(fill));
+ }
return wv;
}
@@ -443,6 +474,7 @@ scm_i_make_weak_vector_from_list (scm_t_bits type, SCM lst)
scm_is_pair (lst);
lst = SCM_CDR (lst), elt++)
{
+ SCM_I_REGISTER_DISAPPEARING_LINK((GC_PTR) elt, (GC_PTR) SCM_UNPACK(SCM_CAR(lst)));
*elt = SCM_CAR (lst);
}
--
1.6.5.7
--
Mike: I WAS NOT MICROWAVED.
