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I haven't tried it, but I would expect `shm_open(3)` to also work in a pinch. The downside there is probably a smaller maximum process size (4MB?), but that's plenty for most uses.

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On Linux, shm_open(3) just creates a regular file under the tmpfs mounted at /dev/shm. It won't work if the program doesn't have permission to create files there.

Sure, but isn’t that equally true for the tmpfs that memfds use? I’d expect normal userspace programs to have access to both under most conditions, including when all disk-backed file systems are read-only.

Edit: I was wrong about the names given to memfd objects, I thought they showed up under /dev somewhere but they’re purely for debugging purposes.

memfd is a tmpfs file descriptor, but does not use any mounted tmpfs filesystem. It works no matter what filesystems are mounted or access you have.

It's truly great for situations where APIs refuse to take anything other than files and you don't worry about cleanup. Ex: loading certs from memory into a python openssl context.

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