Issue 4509: Do not modify an array if we know the change would result
in a failure due to exported buffers.
diff --git a/Modules/arraymodule.c b/Modules/arraymodule.c
index 6dc46ad..256bcd8 100644
--- a/Modules/arraymodule.c
+++ b/Modules/arraymodule.c
@@ -735,6 +735,14 @@
ihigh = Py_SIZE(a);
item = a->ob_item;
d = n - (ihigh-ilow);
+ /* Issue #4509: If the array has exported buffers and the slice
+ assignment would change the size of the array, fail early to make
+ sure we don't modify it. */
+ if (d != 0 && a->ob_exports > 0) {
+ PyErr_SetString(PyExc_BufferError,
+ "cannot resize an array that is exporting buffers");
+ return -1;
+ }
if (d < 0) { /* Delete -d items */
memmove(item + (ihigh+d)*a->ob_descr->itemsize,
item + ihigh*a->ob_descr->itemsize,