Bug report

Bug description:

ShareableList(sequence) creates its shared memory block before packing the values into it. If packing then fails for a value of a supported type, such as an int outside the signed 64-bit range, the exception propagates and the new block stays behind, with no object left through which the caller could unlink it.

from multiprocessing import shared_memory

try:
    shared_memory.ShareableList([2**63], name='psm_demo')
except Exception as e:
    print(type(e).__name__, e)

shm = shared_memory.SharedMemory('psm_demo')  # succeeds; expected FileNotFoundError
print(shm.size)
shm.close()
shm.unlink()

Without name=, each failed call leaves one randomly named psm_* block in /dev/shm until the resource tracker exits.

CPython versions tested on:

CPython main branch

Operating systems tested on:

Linux

Linked PRs

• gh-161098: Unlink the new ShareableList block if packing a value fails #161099
• [3.14] gh-161098: Unlink the new ShareableList block if packing a value fails (GH-161099) #161131
• [3.15] gh-161098: Unlink the new ShareableList block if packing a value fails (GH-161099) #161132