Re: [Libguestfs] [PATCH] v2v: fixed file_owner function

On Wed, 3 Aug 2016 11:14:26 +0100 "Richard W.M. Jones" <rjones(a)redhat.com&gt; wrote: > On Mon, Aug 01, 2016 at 02:46:14PM +0200, Tomáš Golembiovský wrote: > > What was happening in file_owner function did not match the description > > in the comment. When a path is owned by multiple packages the returned > > string was in fact a concatenation of the names of all packages that own > > it. E.g. for `Linux.is_file_owned g inspect "/etc"` the returned value > > was "filesystemyum" (i.e. "filesystem" + "yum"). > > > > Signed-off-by: Tomáš Golembiovský <tgolembi(a)redhat.com&gt; > > --- > > v2v/linux.ml | 8 ++++++-- > > 1 file changed, 6 insertions(+), 2 deletions(-) > > > > diff --git a/v2v/linux.ml b/v2v/linux.ml > > index d20194b..aeff5c5 100644 > > --- a/v2v/linux.ml > > +++ b/v2v/linux.ml > > @@ -99,14 +99,18 @@ let rec file_owner g inspect path = > > (* Although it is possible in RPM for multiple packages to own > > * a file, this deliberately only returns one package. > > *) > > - let cmd = [| "rpm"; "-qf"; "--qf"; "%{NAME}"; path |] in > > + let cmd = [| "rpm"; "-qf"; "--qf"; "%{NAME}\\n"; path |] in > > debug "%s" (String.concat " " (Array.to_list cmd)); > > - (try g#command cmd > > + (try > > + let pkgs = g#command_lines cmd in > > + pkgs.(0) > > with Guestfs.Error msg as exn -> > > if String.find msg "is not owned" >= 0 then > > raise Not_found > > else > > raise exn > > + | Invalid_argument msg -> > > + raise Not_found > > My concern/confusion about this patch is what raises Invalid_argument? > > I'm assuming it's the array index, which could raise `Invalid_argument > "index out of bounds"' if the g#command_lines returns a zero-length > list, but then my question would be why is the rpm command not > returning any lines? > > Even if this can happen, the exception shouldn't be converted to > Not_found. It should be an internal error or the exception should be > left unchanged. Yes, it is to catch the case when rpm reports nothing. Don't know if/when this can happen. Do you prefer an error in the exception handler (instead of raise Not_found), or should I check the array length (and report error) before accessing it?