Re: [Qemu-devel] [PATCH 10/10] qapi: Clean up null checking in generated visitors

[Eric Blake <eblake@redhat.com>]

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On 02/06/2014 07:30 AM, Markus Armbruster wrote:
> Visitors get passed a pointer to the visited object.  The generated
> visitors try to cope with this pointer being null in some places, for
> instance like this:
> 
>     visit_start_optional(m, obj ? &(*obj)->has_name : NULL, "name", &err);
> 
> visit_start_optional() passes its second argument to Visitor method
> start_optional.  Two out of two methods dereference it
> unconditionally.

Let's see if I can find them without Coverity's help...

opts-visitor.c:opts_start_optional
qmp-input-visitor.c:qmp_input_start_optional
string-input-visitor.c:parse_start_optional

Your counting is off :)  All three unconditionally dereference.

[While at it, this code style from parse_start_optional, and similar in
other locations, is rather verbose:

    if (!siv->string) {
        *present = false;
        return;
    }

    *present = true;
}

Shorter would be:

    *present = !!siv->string;
}

but that doesn't affect this patch]

> 
> I fail to see how hits pointer could legitimately be null.
> 
> All this useless null checking is highly redundant, which Coverity
> duly reports.  About 200 times.
> 
> Remove the useless null checks.
> 
> Signed-off-by: Markus Armbruster <armbru@redhat.com>
> ---
>  scripts/qapi-visit.py | 14 +++++++-------
>  1 file changed, 7 insertions(+), 7 deletions(-)

Reviewed-by: Eric Blake <eblake@redhat.com>

-- 
Eric Blake   eblake redhat com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org


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