[Libguestfs] [PATCH] virt-sysprep:add logging feature
Wanlong Gao
gaowanlong at cn.fujitsu.com
Wed Apr 11 00:40:36 UTC 2012
On 04/06/2012 04:56 PM, Richard W.M. Jones wrote:
> 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
Could you please point out the error I met here?
File "sysprep_operation.mli", line 23, characters 17-19:
Error: Unbound type parameter 'a
make: *** [sysprep_operation.cmi] Error 2
make: Leaving directory `/work/git/libguestfs/sysprep'
Thanks,
Wanlong Gao
> 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.
>
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