micropython/tests/basics/bytearray_add_self.py

# add a bytearray to itself
# This is not supported by CPython as of 3.11.18.

b = bytearray(b"123456789")
for _ in range(4):
    c = bytearray(b)  # extra allocation increases chance 'b' has to relocate
    b += b
print(b)
py/objarray: Fix use-after-free if extending a bytearray from itself. Two cases, one assigning to a slice. Closes https://github.com/micropython/micropython/issues/13283 Second is extending a slice from itself, similar logic. In both cases the problem occurs when m_renew causes realloc to move the buffer, leaving a dangling pointer behind. There are more complex and hard to fix cases when either argument is a memoryview into the buffer, currently resizing to a new address breaks memoryviews into that object. Reproducing this bug and confirming the fix was done by running the unix port under valgrind with GC-aware extensions. Note in default configurations with GIL this bug exists but has no impact (the free buffer won't be reused while the function is still executing, and is no longer referenced after it returns). Signed-off-by: Angus Gratton <angus@redyak.com.au> 2024-02-12 22:24:36 +00:00			`# add a bytearray to itself`
			`# This is not supported by CPython as of 3.11.18.`

			`b = bytearray(b"123456789")`
			`for _ in range(4):`
			`c = bytearray(b) # extra allocation increases chance 'b' has to relocate`
			`b += b`
			`print(b)`