Re: [Qemu-devel] [PATCH 07/18] qom: add link properties

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

On 12/01/2011 07:50 AM, Avi Kivity wrote:
> On 12/01/2011 03:47 PM, Anthony Liguori wrote:
>>> What if it's called with the output visitor? (warning: confusing
>>> convention).
>>
>> The reason there's a single Visitor type that works for both input and
>> output visitors is to make it so you can write a single visit function
>> that works for input and output.  This works very well for most cases
>> (in fact, QAPI makes heavy use of it).
>>
>> That said, I'm starting to feel like there should be a separate input
>> and output visitor interface.  It would make a number of things (like
>> visiting lists) significantly simpler.
>
> Perhaps.  But that's independent of the issue here.  No matter how many
> visitors you have, you never change a gchar in a string in place, you
> always allocate a new string (or you can't change the string length).
> So the type needs to be const gchar **, not gchar **.

While you are correct, I tend to use 'gchar *' and 'const gchar *' to indicate 
ownership.  If you have a function that takes a 'const gchar **', the 
expectation is that you wouldn't have to free the return value since g_free() 
takes a non-const pointer.  You would, in fact, have to cast away the const in 
order to even call free.

IOW, if you call visit_type_str() and it returns a newly allocated string to 
you, it's your responsibility to free it.

Regards,

Anthony Liguori

>