passing zero to PTR_ERR() warnings

Everyone seems to be hitting this warning, but I can't reproduce it at
all.  It came from a bug when I made pointers unsigned...

I though I fixed it in commit 8a9817501654 ("zero_to_err_ptr:  fix fall
out from unsigned pointer changes and improve") but now I can't
reproduce it even when I revert that patch.

I'm using a clean smatch clone and a clean kernel clone, but I just
can't trigger false positives.  I get valid warnings still but not the
false positives.

Can anyone help me figure this out?

regards,
dan carpenter