From acfbb9febd024475bdcb4ebbe2ec8c0e9a652275 Mon Sep 17 00:00:00 2001
From: Damien George
Date: Thu, 15 Aug 2019 23:02:04 +1000
Subject: py/objarray: Fix amount of free space in array when doing slice
 assign.

Prior to this patch the amount of free space in an array (including
bytearray) was not being maintained correctly for the case of slice
assignment which changed the size of the array.  Under certain cases (as
encoded in the new test) it was possible that the array could grow beyond
its allocated memory block and corrupt the heap.

Fixes issue #4127.
---
 tests/basics/bytearray_slice_assign.py | 7 +++++++
 1 file changed, 7 insertions(+)

(limited to 'tests')

diff --git a/tests/basics/bytearray_slice_assign.py b/tests/basics/bytearray_slice_assign.py
index 7f7d1d119..fa7878e10 100644
--- a/tests/basics/bytearray_slice_assign.py
+++ b/tests/basics/bytearray_slice_assign.py
@@ -59,3 +59,10 @@ print(b)
 b = bytearray(2)
 b[1:1] = b"12345"
 print(b)
+
+# Growth of bytearray via slice extension
+b = bytearray(b'12345678')
+b.append(57) # expand and add a bit of unused space at end of the bytearray
+for i in range(400):
+    b[-1:] = b'ab' # grow slowly into the unused space
+print(len(b), b)
-- 
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