make-uniform-vector bit vector versus array-set!

make-uniform-vector bit vector versus array-set!

[Kevin Ryde]

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In 1.8 there seems to be something a bit evil in array-set! on a bit
vector created by make-uniform-vector,

	guile> (define a (make-uniform-vector 15 #t #t))
	guile> a
	#*111111111111111
	guile> (array-set! a #f 0)
	guile> a
	(2207 . #<smob 80ba960>)

I don't understand all that stuff, but I got some joy from this
change.  Can someone (Marius?) confirm or deny?

        * unif.c (bitvector_set): Should be h->writable_elements not
        h->elements, the latter results in a segv in array-set! on a bit
        vector.


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--- unif.c.~1.192.2.2.~	2006-02-14 08:59:03.000000000 +1100
+++ unif.c	2006-02-25 18:22:35.000000000 +1100
@@ -380,9 +380,9 @@
   pos += scm_array_handle_bit_elements_offset (h);
   mask = 1l << (pos % 32);
   if (scm_to_bool (val))
-    ((scm_t_uint32 *)h->elements)[pos/32] |= mask;
+    ((scm_t_uint32 *)h->writable_elements)[pos/32] |= mask;
   else
-    ((scm_t_uint32 *)h->elements)[pos/32] &= ~mask;
+    ((scm_t_uint32 *)h->writable_elements)[pos/32] &= ~mask;
 }
 
 static void

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Re: make-uniform-vector bit vector versus array-set!

[Marius Vollmer]

Kevin Ryde <user42@zip.com.au> writes:

> I don't understand all that stuff, but I got some joy from this
> change.  Can someone (Marius?) confirm or deny?
>
>         * unif.c (bitvector_set): Should be h->writable_elements not
>         h->elements, the latter results in a segv in array-set! on a bit
>         vector.

This is the right fix.  Thanks!

Readers like bitvector_ref should use h->elements, and setters like
bitvector_set should use h->writable_elements.  Those two pointers are
set up by memoize_ref and memoize_set, respectively.

-- 
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