Re: [PATCH v6 03/11] scripts: add coccinelle script to use auto propagated errp

[Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>]

10.01.2020 22:41, Vladimir Sementsov-Ogievskiy wrote:
> Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
> ---
> 
> CC: Cornelia Huck <cohuck@redhat.com>
> CC: Eric Blake <eblake@redhat.com>
> CC: Kevin Wolf <kwolf@redhat.com>
> CC: Max Reitz <mreitz@redhat.com>
> CC: Greg Kurz <groug@kaod.org>
> CC: Stefan Hajnoczi <stefanha@redhat.com>
> CC: Stefano Stabellini <sstabellini@kernel.org>
> CC: Anthony Perard <anthony.perard@citrix.com>
> CC: Paul Durrant <paul@xen.org>
> CC: "Philippe Mathieu-Daudé" <philmd@redhat.com>
> CC: Laszlo Ersek <lersek@redhat.com>
> CC: Gerd Hoffmann <kraxel@redhat.com>
> CC: Stefan Berger <stefanb@linux.ibm.com>
> CC: Markus Armbruster <armbru@redhat.com>
> CC: Michael Roth <mdroth@linux.vnet.ibm.com>
> CC: qemu-block@nongnu.org
> CC: xen-devel@lists.xenproject.org
> 
>   include/qapi/error.h                          |   3 +
>   scripts/coccinelle/auto-propagated-errp.cocci | 139 ++++++++++++++++++
>   2 files changed, 142 insertions(+)
>   create mode 100644 scripts/coccinelle/auto-propagated-errp.cocci
> 
> diff --git a/include/qapi/error.h b/include/qapi/error.h
> index 532b9afb9e..dcfb77e107 100644
> --- a/include/qapi/error.h
> +++ b/include/qapi/error.h
> @@ -141,6 +141,9 @@
>    *         ...
>    *     }
>    *
> + * For mass conversion use script
> + *   scripts/coccinelle/auto-propagated-errp.cocci
> + *
>    *
>    * Receive and accumulate multiple errors (first one wins):
>    *     Error *err = NULL, *local_err = NULL;
> diff --git a/scripts/coccinelle/auto-propagated-errp.cocci b/scripts/coccinelle/auto-propagated-errp.cocci
> new file mode 100644
> index 0000000000..6c72a5049f
> --- /dev/null
> +++ b/scripts/coccinelle/auto-propagated-errp.cocci
> @@ -0,0 +1,139 @@
> +// Use ERRP_AUTO_PROPAGATE (see include/qapi/error.h)
> +//
> +// Copyright (c) 2020 Virtuozzo International GmbH.
> +//
> +// This program is free software; you can redistribute it and/or modify
> +// it under the terms of the GNU General Public License as published by
> +// the Free Software Foundation; either version 2 of the License, or
> +// (at your option) any later version.
> +//
> +// This program is distributed in the hope that it will be useful,
> +// but WITHOUT ANY WARRANTY; without even the implied warranty of
> +// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> +// GNU General Public License for more details.
> +//
> +// You should have received a copy of the GNU General Public License
> +// along with this program.  If not, see <http://www.gnu.org/licenses/>.
> +//
> +// Usage example:
> +// spatch --sp-file scripts/coccinelle/auto-propagated-errp.cocci \
> +//  --macro-file scripts/cocci-macro-file.h --in-place --no-show-diff \
> +//  blockdev-nbd.c qemu-nbd.c {block/nbd*,nbd/*,include/block/nbd*}.[hc]
> +
> +@@
> +// Add invocation to errp-functions where necessary
> +// We should skip functions with "Error *const *errp"
> +// parameter, but how to do it with coccinelle?
> +// I don't know, so, I skip them by function name regex.
> +// It's safe: if we not skip some functions with
> +// "Error *const *errp", ERRP_AUTO_PROPAGATE invocation
> +// will fail to compile, because of const violation.
> +identifier fn !~ "error_append_.*_hint";
> +identifier local_err, errp;

Hmm.

Note, that in new version I define errp as "identifier", which means,
that we'll match Error ** parameters with other names..

Still, our ERRP_AUTO_PROPAGATE assumes that parameter called errp, and
I'd prefere not to change it.

We can ignore this fact for now: inappropriately named errp parameter will
break compilation in ERRP_AUTO_PROPAGATE() invocation, so it's safe enough.
(Hope, there are no functions with two Error** parameters)

Or we can revert errp to be symbol again.

> +@@
> +
> + fn(..., Error **errp, ...)
> + {
> ++   ERRP_AUTO_PROPAGATE();
> +    <+...
> +        when != ERRP_AUTO_PROPAGATE();
> +(
> +    error_append_hint(errp, ...);
> +|
> +    error_prepend(errp, ...);
> +|
> +    Error *local_err = NULL;
> +)
> +    ...+>
> + }
> +
> +@rule1@
> +// We do not inherit from previous rule, as we want to match
> +// also functions, which already had ERRP_AUTO_PROPAGATE
> +// invocation.
> +identifier fn !~ "error_append_.*_hint";
> +identifier local_err, errp;
> +@@
> +
> + fn(..., Error **errp, ...)
> + {
> +     <...
> +-    Error *local_err = NULL;
> +     ...>
> + }
> +
> +@@
> +// Handle pattern with goto, otherwise we'll finish up
> +// with labels at function end which will not compile.
> +identifier rule1.fn, rule1.local_err, rule1.errp;
> +identifier OUT;
> +@@
> +
> + fn(...)
> + {
> +     <...
> +-    goto OUT;
> ++    return;
> +     ...>
> +- OUT:
> +-    error_propagate(errp, local_err);
> + }
> +
> +@@
> +identifier rule1.fn, rule1.local_err, rule1.errp;
> +expression list args; // to reindent error_propagate_prepend
> +@@
> +
> + fn(...)
> + {
> +     <...
> +(
> +-    error_free(local_err);
> +-    local_err = NULL;
> ++    error_free_errp(errp);
> +|
> +-    error_free(local_err);
> ++    error_free_errp(errp);
> +|
> +-    error_report_err(local_err);
> ++    error_report_errp(errp);
> +|
> +-    warn_report_err(local_err);
> ++    warn_report_errp(errp);
> +|
> +-    error_propagate_prepend(errp, local_err, args);
> ++    error_prepend(errp, args);
> +|
> +-    error_propagate(errp, local_err);
> +)
> +     ...>
> + }
> +
> +@@
> +identifier rule1.fn, rule1.local_err, rule1.errp;
> +@@
> +
> + fn(...)
> + {
> +     <...
> +(
> +-    &local_err
> ++    errp
> +|
> +-    local_err
> ++    *errp
> +)
> +     ...>
> + }
> +
> +@@
> +identifier rule1.fn, rule1.errp;
> +@@
> +
> + fn(...)
> + {
> +     <...
> +- *errp != NULL
> ++ *errp
> +     ...>
> + }
> 


-- 
Best regards,
Vladimir