Hi, I tried replicating this by truncating normal files but that doesn't crash. The above mentioned call of ftruncate only crashes for when the file descriptor passed points to a shared memory segment.
And only, multiprocessing.shared_memory is currently creating shared_memory using _posixshmem.shm_open.

So, it can be fixed in ftruncate implementation or this can also be handled by multiprocessing.shared_memory.

Please let me know your thoughts about the same.