Re: [Qemu-block] [PATCH v3 1/8] qapi: Add default-variant for flat unions

[Eric Blake]

On 2/6/19 1:55 PM, Max Reitz wrote:
> This patch allows specifying a discriminator that is an optional member
> of the base struct.  In such a case, a default value must be provided
> that is used when no value is given.
> 
> Signed-off-by: Max Reitz <address@hidden>
> ---
>  qapi/introspect.json           |  8 +++++
>  scripts/qapi/common.py         | 58 ++++++++++++++++++++++++++++------
>  scripts/qapi/doc.py            | 10 ++++--
>  scripts/qapi/introspect.py     | 10 ++++--
>  scripts/qapi/visit.py          | 13 ++++++++
>  tests/qapi-schema/test-qapi.py |  2 ++
>  6 files changed, 86 insertions(+), 15 deletions(-)

Missing a change to docs/devel/qapi-code-gen.txt? [re-reads diffstat in
cover letter...] Oh, you got that later in the series. Maybe those two
patches are worth squashing?

> +++ b/scripts/qapi/visit.py
> @@ -77,6 +77,19 @@ void visit_type_%(c_name)s_members(Visitor *v, %(c_name)s 
> *obj, Error **errp)
>          ret += gen_endif(memb.ifcond)
>  
>      if variants:
> +        if variants.default_tag_value is not None:
> +            ret += mcgen('''
> +    if (!obj->has_%(c_name)s) {
> +        obj->has_%(c_name)s = true;
> +        obj->%(c_name)s = %(enum_const)s;
> +    }
> +''',
> +                         c_name=c_name(variants.tag_member.name),
> +                         enum_const=c_enum_const(
> +                             variants.tag_member.type.name,
> +                             variants.default_tag_value,
> +                             variants.tag_member.type.prefix))
> +

I like that you de-sugar it as early in the input parse as possible.

Markus may have comments, but it looks reasonable to me.

Reviewed-by: Eric Blake <address@hidden>

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

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