From 73c58150f53d9d828c4fc8fb455cca6831eb8ddd Mon Sep 17 00:00:00 2001
From: Damien George
Date: Mon, 20 Apr 2020 23:04:40 +1000
Subject: extmod/modbtree: Retain reference to underlying stream so it's not
 GC'd.

For ports that have a system malloc which is not garbage collected (eg
unix, esp32), the stream object for the DB must be retained separately to
prevent it from being reclaimed by the MicroPython GC (because the
berkeley-db library uses malloc to allocate the DB structure which stores
the only reference to the stream).

Although in some cases the user code will explicitly retain a reference to
the underlying stream because it needs to call close() on it, this is not
always the case, eg in cases where the DB is intended to live forever.

Fixes issue #5940.
---
 tests/extmod/btree_gc.py     | 23 +++++++++++++
 tests/extmod/btree_gc.py.exp | 80 ++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 103 insertions(+)
 create mode 100644 tests/extmod/btree_gc.py
 create mode 100644 tests/extmod/btree_gc.py.exp

(limited to 'tests/extmod')

diff --git a/tests/extmod/btree_gc.py b/tests/extmod/btree_gc.py
new file mode 100644
index 000000000..153f4e7d7
--- /dev/null
+++ b/tests/extmod/btree_gc.py
@@ -0,0 +1,23 @@
+# Test btree interaction with the garbage collector.
+
+try:
+    import btree, uio, gc
+except ImportError:
+    print("SKIP")
+    raise SystemExit
+
+N = 80
+
+# Create a BytesIO but don't keep a reference to it.
+db = btree.open(uio.BytesIO(), pagesize=512)
+
+# Overwrite lots of the Python stack to make sure no reference to the BytesIO remains.
+x = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
+
+# Write lots of key/value pairs, which fill up the DB and also allocate temporary heap
+# memory due to the string addition, and do a GC collect to verify that the BytesIO
+# is not collected.
+for i in range(N):
+    db[b"thekey" + str(i)] = b"thelongvalue" + str(i)
+    print(db[b"thekey" + str(i)])
+    gc.collect()
diff --git a/tests/extmod/btree_gc.py.exp b/tests/extmod/btree_gc.py.exp
new file mode 100644
index 000000000..e7b8d5672
--- /dev/null
+++ b/tests/extmod/btree_gc.py.exp
@@ -0,0 +1,80 @@
+b'thelongvalue0'
+b'thelongvalue1'
+b'thelongvalue2'
+b'thelongvalue3'
+b'thelongvalue4'
+b'thelongvalue5'
+b'thelongvalue6'
+b'thelongvalue7'
+b'thelongvalue8'
+b'thelongvalue9'
+b'thelongvalue10'
+b'thelongvalue11'
+b'thelongvalue12'
+b'thelongvalue13'
+b'thelongvalue14'
+b'thelongvalue15'
+b'thelongvalue16'
+b'thelongvalue17'
+b'thelongvalue18'
+b'thelongvalue19'
+b'thelongvalue20'
+b'thelongvalue21'
+b'thelongvalue22'
+b'thelongvalue23'
+b'thelongvalue24'
+b'thelongvalue25'
+b'thelongvalue26'
+b'thelongvalue27'
+b'thelongvalue28'
+b'thelongvalue29'
+b'thelongvalue30'
+b'thelongvalue31'
+b'thelongvalue32'
+b'thelongvalue33'
+b'thelongvalue34'
+b'thelongvalue35'
+b'thelongvalue36'
+b'thelongvalue37'
+b'thelongvalue38'
+b'thelongvalue39'
+b'thelongvalue40'
+b'thelongvalue41'
+b'thelongvalue42'
+b'thelongvalue43'
+b'thelongvalue44'
+b'thelongvalue45'
+b'thelongvalue46'
+b'thelongvalue47'
+b'thelongvalue48'
+b'thelongvalue49'
+b'thelongvalue50'
+b'thelongvalue51'
+b'thelongvalue52'
+b'thelongvalue53'
+b'thelongvalue54'
+b'thelongvalue55'
+b'thelongvalue56'
+b'thelongvalue57'
+b'thelongvalue58'
+b'thelongvalue59'
+b'thelongvalue60'
+b'thelongvalue61'
+b'thelongvalue62'
+b'thelongvalue63'
+b'thelongvalue64'
+b'thelongvalue65'
+b'thelongvalue66'
+b'thelongvalue67'
+b'thelongvalue68'
+b'thelongvalue69'
+b'thelongvalue70'
+b'thelongvalue71'
+b'thelongvalue72'
+b'thelongvalue73'
+b'thelongvalue74'
+b'thelongvalue75'
+b'thelongvalue76'
+b'thelongvalue77'
+b'thelongvalue78'
+b'thelongvalue79'
-- 
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