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

[Markus Armbruster <armbru@xxxxxxxxxx>]

Eric Blake <eblake@xxxxxxxxxx> writes:

> 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?

We can try for the next batch.

>> +@ 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.

Yes.

> 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>

Thanks!