Chown :groupName and chgrp provide uid as 4294967295L

[LuQQiu]

When we implement the jnr-fuse chown() function in Alluxio/alluxio#8010, we find that if users want to change group without change user, the chown() function will provide the uid as 4294967295L instead of -1.

4294967295L is just unsigned long -1.
According to https://linux.die.net/man/3/chown it looks like -1 should be the default.

Is jnr-fuse intended to use 4294967295L instead of -1?

[SerCeMan]

Hi, @LuQQiu!

Looking at the native chown in libfuse, https://github.com/libfuse/libfuse/blob/c779a4ee2b8f61e54442d9f65c0efcee18b805cb/lib/fuse.c#L2123-L2125, uid has a type uid_t. On different platforms uid_t might be signed or unsigned, is it signed on your machine?

[LuQQiu]

Hi @SerCeMan
In my local mac and remote ec2 (Amazon linux) instances, uid is unsigned 4294967295L.
It seems that the 4294967295 uid_t is given by libfuse and does not change in jnr-fuse.

The number(-1 or 4294967295) is likely to depend on different platforms, I would better to check both in chown implementation.

Thanks for your fast reply and great help!

[LuQQiu]

Confirmed that both uid_t and gid_t can be signed or unsigned based on the platforms. We better check both

private static final long ID_NOT_SET_VALUE = -1;
private static final long ID_NOT_SET_VALUE_UNSIGNED = 4294967295L;