Are shared memory initial values well-defined? [duplicate]

Question

The following code runs without error on macOS:

from multiprocessing.shared_memory import SharedMemory shm = SharedMemory(create=True, size=4) for b in shm.buf: assert b == 0 shm.close() shm.unlink()

This indicates that the shared memory segment is all binary zero.

However, what I want to know is whether this is well-defined behaviour across all platforms

It's better to consider the contents indeterminate, and always explicitly initialize it if you need to. — Some programmer dude
– Some programmer dude, Commented Sep 2, 2022 at 7:22
It's more about OS. In Windows SharedMemory relies on CreateFileMapping()/OpenFileMapping() calls, in POSIX it calls shm_open(). — Olvin Roght
– Olvin Roght, Commented Sep 2, 2022 at 7:23
@VsevolodTimchenko Thank you . I did search but obviously didn't use the right terms — jackal
– jackal, Commented Sep 2, 2022 at 7:23

Vsevolod Timchenko · Accepted Answer · 2022-09-02 07:19:51Z

This is a duplicate:

Why does python's SharedMemory seem to initialize arrays to zeros

This is operating system dependent. Python doesn't initialize the memory - it just takes the virtual memory address offered by the operating system.

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