Re: [Libguestfs] [PATCH] virt-sysprep:add logging feature
On Fri, Apr 06, 2012 at 01:37:33PM +0800, Wanlong Gao wrote:
Hi Rich,
I tried to implement the logging feature, but I can't though
compiling with this patch now, could you please give me
some comments?
The error message is below,
---
ocamlfind ocamlopt -g -warn-error CDEFLMPSUVYZX -package unix -I ../src/.libs -I ../ocaml
-c sysprep_operation.ml -o sysprep_operation.cmx
File "sysprep_operation.ml", line 1, characters 0-1:
Error: The implementation sysprep_operation.ml
does not match the interface sysprep_operation.cmi:
Type declarations do not match:
type operation = {
name : string;
pod_description : string;
extra_args : ((Arg.key * Arg.spec * Arg.doc) * string) list;
perform : Guestfs.guestfs -> string -> bool -> flag list;
}
is not included in
type operation = {
name : string;
pod_description : string;
extra_args : ((Arg.key * Arg.spec * Arg.doc) * string) list;
perform : Guestfs.guestfs -> string -> flag list;
}
The types for field perform are not equal.
Indeed they are not! The implementation (*.ml) has changed:
- perform : Guestfs.guestfs -> string -> flag list;
+ perform : Guestfs.guestfs -> string -> bool -> flag list;
but you must make an equivalent change to the interface (in
sysprep_operation.mli) -- adding the extra debug flag.
May I suggest another way to do this which is a bit more natural. Use
a function. Declare it as:
type debug_fn = ('a, unit, string, unit) format4 -> 'a
type operation = { ...
perform : Guestfs.guestfs -> debug:debug_fn -> string -> flag list
}
Implementations would just do this:
let foo_perform g ~debug root =
debug "I'm calling foo %s" root;
...
The main function does this:
let debug fs =
ksprintf (fun str -> if show_log then prerr_endline str) fs
...
Sysprep_operations.perform_operations ?operations ~debug g root
Note that the debug function prints conditionally, based on whether
show_log is set or not.
Rich.
--
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
libguestfs lets you edit virtual machines. Supports shell scripting,
bindings from many languages. http://libguestfs.org