Re: [Xen-devel] [PATCH V5 19/32] libxl/gentypes.py: don't generate default values

[Wei Liu <wei.liu2@xxxxxxxxxx>]

On Tue, May 20, 2014 at 02:29:09PM +0100, Ian Campbell wrote:
> On Tue, 2014-05-13 at 22:54 +0100, Wei Liu wrote:
> > If a type has init_val defined and a field of the type has the value of
> > init_val, there's no need to generate output for that field.
> 
> Please can you explain why there is no need. And I think you need to
> mention JSON here somewhere.
> 

Sure.

"If a type has init_val defined and a field of the type has the value of
init_val, there's no need to generate output for that field in JSON
output. When the parser consumes that generated JSON object, all default
values should be automatically filled in."

> > Also define a bunch of init_vals for enumeration types.
> 
> I'm not convinced by this. If a type has no initval then you should
> compare it to zero, which is a valid thing to do even for an enum.
> 

What I really did here for enum type was to replace magic number 0 (or
any other predefined value) with a meaningful macro, so that the
generated code can have
 if (FOO == LIBXL_FOO_DEFAULT)
other than
 if (FOO == 0)
which has better readability.

> NB you changed the init_val for some typesto (e.g. from 1 to
> LIBXL_VGA_INTERFACE_TYPE_CIRRUS), which is a no semantic change change,
> but did mean I had to double check.
> 

Corret, I didn't intend to make any semantic changes.

Wei.


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