Re: [Qemu-devel] [PATCH 2/9] qapi: allow build_params to return "void"

[Peter Xu]

On Thu, Jul 05, 2018 at 08:02:21AM +0200, Markus Armbruster wrote:
> Peter Xu <address@hidden> writes:
> 
> > When there is no parameter at all for a function prototype, return
> > "void" for the parameter list.  This will happen after the next patch
> > where we removed the Error* for some of the emit functions.
> 
> Error **, actually.  Let's say
> 
>   qapi: Fix build_params() for empty parameter list
> 
>   build_params() returns '' instead of 'void' when there are no
>   parameters.  Can't happen now, but the next commit will change that.

Sure.

> 
> >
> > Signed-off-by: Peter Xu <address@hidden>
> > ---
> >  scripts/qapi/common.py | 4 ++--
> >  1 file changed, 2 insertions(+), 2 deletions(-)
> >
> > diff --git a/scripts/qapi/common.py b/scripts/qapi/common.py
> > index 8b6708dbf1..105c82742f 100644
> > --- a/scripts/qapi/common.py
> > +++ b/scripts/qapi/common.py
> > @@ -1963,7 +1963,7 @@ extern const QEnumLookup %(c_name)s_lookup;
> >  def build_params(arg_type, boxed, extra):
> >      if not arg_type:
> >          assert not boxed
> > -        return extra
> > +        return extra if extra else "void"
> >      ret = ''
> >      sep = ''
> >      if boxed:
> > @@ -1980,7 +1980,7 @@ def build_params(arg_type, boxed, extra):
> >                                c_name(memb.name))
> >      if extra:
> >          ret += sep + extra
> > -    return ret
> > +    return ret if ret else "void"
> >  
> >  
> >  #
> 
> Please use ' instead of " for local consistency.
> 
> Duplicating "if ret else 'void'" minimizes churn, but it's slightly
> ugly.  I append my attempt to avoid it.  What do you think?
> 
> 
> diff --git a/scripts/qapi/common.py b/scripts/qapi/common.py
> index 8b6708dbf1..01384c5360 100644
> --- a/scripts/qapi/common.py
> +++ b/scripts/qapi/common.py
> @@ -1961,15 +1961,13 @@ extern const QEnumLookup %(c_name)s_lookup;
>  
>  
>  def build_params(arg_type, boxed, extra):
> -    if not arg_type:
> -        assert not boxed
> -        return extra
>      ret = ''
>      sep = ''
>      if boxed:
> +        assert arg_type
>          ret += '%s arg' % arg_type.c_param_type()
>          sep = ', '
> -    else:
> +    elif arg_type:
>          assert not arg_type.variants
>          for memb in arg_type.members:
>              ret += sep
> @@ -1980,7 +1978,7 @@ def build_params(arg_type, boxed, extra):
>                                c_name(memb.name))
>      if extra:
>          ret += sep + extra
> -    return ret
> +    return ret if ret else 'void'

Yeah, this looks good to me.

Thanks,

-- 
Peter Xu