Re: [PATCH v12 2/8] scripts: Coccinelle script to use ERRP_AUTO_PROPAGATE()

[Eric Blake <eblake@xxxxxxxxxx>]

On 7/7/20 11:50 AM, Markus Armbruster wrote:
> From: Vladimir Sementsov-Ogievskiy <vsementsov@xxxxxxxxxxxxx>
>
> Script adds ERRP_AUTO_PROPAGATE macro invocation where appropriate and
> does corresponding changes in code (look for details in
> include/qapi/error.h)
>
> Usage example:
> spatch --sp-file scripts/coccinelle/auto-propagated-errp.cocci \
>   --macro-file scripts/cocci-macro-file.h --in-place --no-show-diff \
>   --max-width 80 FILES...
>
> Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@xxxxxxxxxxxxx>
> Reviewed-by: Markus Armbruster <armbru@xxxxxxxxxx>
> Signed-off-by: Markus Armbruster <armbru@xxxxxxxxxx>
> ---
>   scripts/coccinelle/auto-propagated-errp.cocci | 337 ++++++++++++++++++
>   include/qapi/error.h                          |   3 +
>   MAINTAINERS                                   |   1 +
>   3 files changed, 341 insertions(+)
>   create mode 100644 scripts/coccinelle/auto-propagated-errp.cocci
Needs a tweak if we go with ERRP_GUARD.  But that's easy.

> +
> +// Convert special case with goto separately.
> +// I tried merging this into the following rule the obvious way, but
> +// it made Coccinelle hang on block.c
> +//
> +// Note interesting thing: if we don't do it here, and try to fixup
> +// "out: }" things later after all transformations (the rule will be
> +// the same, just without error_propagate() call), coccinelle fails to
> +// match this "out: }".
"out: }" is not valid C; would referring to "out: ; }" fare any better?

> +@ disable optional_qualifier@
> +identifier rule1.fn, rule1.local_err, out;
> +symbol errp;
> +@@
> +
> + fn(..., Error ** ____, ...)
> + {
> +     <...
> +-    goto out;
> ++    return;
> +     ...>
> +- out:
> +-    error_propagate(errp, local_err);
> + }
> +
> +// Convert most of local_err related stuff.
> +//
> +// Note, that we inherit rule1.fn and rule1.local_err names, not
> +// objects themselves. We may match something not related to the
> +// pattern matched by rule1. For example, local_err may be defined with
> +// the same name in different blocks inside one function, and in one
> +// block follow the propagation pattern and in other block doesn't.
> +//
> +// Note also that errp-cleaning functions
> +//   error_free_errp
> +//   error_report_errp
> +//   error_reportf_errp
> +//   warn_report_errp
> +//   warn_reportf_errp
> +// are not yet implemented. They must call corresponding Error* -
> +// freeing function and then set *errp to NULL, to avoid further
> +// propagation to original errp (consider ERRP_AUTO_PROPAGATE in use).
> +// For example, error_free_errp may look like this:
> +//
> +//    void error_free_errp(Error **errp)
> +//    {
> +//        error_free(*errp);
> +//        *errp = NULL;
> +//    }
I guess we can still decide later if we want these additional functions, 
or if they will even help after the number of places we have already 
improved after applying this script as-is and with Markus' cleanups in 
place.
While I won't call myself a Coccinelle expert, it at least looks sane 
enough that I'm comfortable if you add:
Reviewed-by: Eric Blake <eblake@xxxxxxxxxx>

--
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3226
Virtualization:  qemu.org | libvirt.org