Looking into this.

Looks like the problem is in attributes, if I remove this line here - https://github.com/uutils/coreutils/blob/main/src/uu/cp/src/cp.rs#L739, it passes.

After a bit more digging, looks like Xattr is the one causing the permission denied error here.

Here is a simpler test case that you can run in an Android emulator in Termux:

touch ~/a
cp -a ~/a ~/b
# no error

touch ~/a
./coreutils/target/debug/coreutils cp -a ~/a ~/b
# permission denied

This is probably because of selinux attributes, but I'm not sure.

Something else that is interesting. With GNU cp, when we specify -a the preserve_xattr is set to true, but this doesn't set the require_preserve_xattr to true. But, if we do --preserve=xattr, the require_preserve_xattr is set to true. Then, when I run cp --preserve=xattr ~/a ~/b on this AVD, I get cp: cannot preserve extended attributes, cp is built without xattr support. So, it looks like the GNU cp doesn't even try setting the attributes in this case.

I can think of three solutions here:

1. Remove the -a parameter from the test.
2. Change the attributes setting code to set only if the value is not set to what you want it to be (because all of the values are default in this case, the problem is trying to set them even to the same value).
3. Ignore the error. Should be similar to what GNU cp does.

What do you think?

Interesting! I think we should match GNU behaviour as much as possible. One thing I'm curious about, is it possible too build cp with xattr support and what is the behaviour then?

@tertsdiepraam looking at https://github.com/coreutils/coreutils/blob/master/src/copy.c#L1427-L1432:

    if (preserve_xattr)
    {
      if (!copy_attr (src_name, source_desc, dst_name, dest_desc, x)
          && x->require_preserve_xattr)
        return_val = false;
    }

If we select -a, we set preserve_xattr to true, and require_preserve_xattr remains at false. Then, when copy attribute fails, since the require_preserve_xattr is set to false, we do not get an error. So, I guess I would ignore the error in case of -a but not if --preserve=xattr is set. I think this calls for a few additional test cases.

I will try building GNU cp with xattr enabled on android.

Again, this is because of #3477.