[PATCH] Allow scm_XXX_writable_elements on empty vectors, even if immutable

[daniel . llorens]

From: Daniel Llorens <daniel.llor...@bluewin.ch>

* libguile/array-handle.c (initialize_vector_handle): Set both element
  pointers to NULL if the vector is empty.
* test-suite/tests/sort.test: Check empty/mutable/immutable vectors with
  sort!.
---
 libguile/array-handle.c    |  6 ++++--
 test-suite/tests/sort.test | 24 ++++++++++++++++++------
 2 files changed, 22 insertions(+), 8 deletions(-)

diff --git a/libguile/array-handle.c b/libguile/array-handle.c
index 3d81efc04..947462a59 100644
--- a/libguile/array-handle.c
+++ b/libguile/array-handle.c
@@ -149,8 +149,10 @@ initialize_vector_handle (scm_t_array_handle *h, size_t 
len,
   h->dim0.ubnd = (ssize_t) (len - 1U);
   h->dim0.inc = 1;
   h->element_type = element_type;
-  h->elements = elements;
-  h->writable_elements = mutable_p ? ((void *) elements) : NULL;
+  /* elements != writable_elements is used to check mutability later on.
+     Ignore it if the array is empty. */
+  h->elements = len==0 ? NULL : elements;
+  h->writable_elements = mutable_p ? ((void *) h->elements) : NULL;
   h->vector = h->array;
   h->vref = vref;
   h->vset = vset;
diff --git a/test-suite/tests/sort.test b/test-suite/tests/sort.test
index 249f890ec..fa1ffd0b6 100644
--- a/test-suite/tests/sort.test
+++ b/test-suite/tests/sort.test
@@ -74,7 +74,9 @@
     (let* ((a (make-typed-array 'f64 0 99 3))
           (v (make-shared-array a (lambda (i) (list (- 98 i) 0)) 99)))
       (randomize-vector! v 99)
-      (sorted? (sort! v <) <)))
+      (sorted? (sort! v <) <))))
+
+(with-test-prefix "stable-sort!"
 
   (pass-if "stable-sort!"
     (let ((v (randomize-vector! (make-vector 1000) 1000)))
@@ -92,11 +94,6 @@
       (randomize-vector! v 1000)
       (sorted? (stable-sort! v <) <))))
 
-
-;;;
-;;; stable-sort
-;;;
-
 (with-test-prefix "stable-sort"
 
   ;; in guile 1.8.0 and 1.8.1 this test failed, an empty list provoked a
@@ -108,3 +105,18 @@
   ;; behavior (integer underflow) leading to crashes.
   (pass-if "empty vector"
     (equal? '#() (stable-sort '#() <))))
+
+
+(with-test-prefix "mutable/immutable arguments"
+
+  (with-test-prefix/c&e "immutable arguments"
+
+    (pass-if "sort! of empty vector"
+      (equal? #() (sort! (vector) <)))
+
+    (pass-if "sort of immutable vector"
+      (equal? #(0 1) (sort #(1 0) <))))
+
+  (pass-if-exception "sort! of mutable vector (compile)"
+      exception:wrong-type-arg
+    (compile '(sort! #(0) <) #:to 'value #:env (current-module))))
-- 
2.11.0