Re: [Qemu-devel] [PATCH 2/2] Introduce macro for defining qdev properties

[Anthony Liguori <aliguori@us.ibm.com>]

Blue Swirl wrote:
>> I'm not sure how to do this without GCC extensions.  We could potentially
>> add macro decorators and use a sparse-like tool to extract property lists
>> automatically from device state.
>>     
>
> Then there is the template way:
>   

Yes, I also considered that.

Another option would be comment decorators along with a post-processor.

typedef struct MyDeviceStruct
{
    SysBusDevice parent;

    /* public */
   QDEV_PROP(uint32_t, queue_depth);
   QDEV_PROP(uint32_t, tx_mitigation_delay);
   QDEV_PROP(CharDriverState *, chr);
} MyDeviceStruct;

Normally, we:

#define QDEV_PROP(a, b) a b

But then we could also do something like:

#define QDEV_PROP(a, b) QPROP_CANARY stringify(a) stringify(b)

Then run through CPP and grep 'CANARY | typedef struct' and then parse 
the output to build the table at build time.

Of course, we could just do QDEV_PROP like I originally proposed and 
then if we ever support something other than GCC, we can introduce a CPP 
post-processor to build the tables at compile time.

This is the approach we're taking for constructors after all.

-- 
Regards,

Anthony Liguori