Re: [PATCH v1 7/9] plugins: add API to return a name for a IO device

["Emilio G. Cota" <cota@braap.org>]

On Mon, Jun 08, 2020 at 09:06:17 +0100, Alex Bennée wrote:
> Emilio G. Cota <cota@braap.org> writes:
> > I'd rather use asprintf(3) and strdup(3) here, so that plugins don't
> > have to worry about glib, and on the QEMU side we don't have to worry
> > about plugins calling free() instead of g_free().
> 
> AFAIK you can actually mix free/g_free because g_free is just a NULL
> checking wrapper around free.

I was just going with the documentation, but you're right:

https://github.com/GNOME/glib/blob/mainline/glib/gmem.c#L196
> void
> g_free (gpointer mem)
> {
>   free (mem);
>   TRACE(GLIB_MEM_FREE((void*) mem));
> }

The NULL-pointer check is done by free(3), though.

> However ideally I'd be passing a
> non-freeable const char to the plugin but I didn't want to expose
> pointers deep inside of QEMU's guts although maybe I'm just being
> paranoid there given you can easily gdb the combined operation anyway.
>
> Perhaps there is a need for a separate memory region where we can store
> copies of strings we have made for the plugins?

I agree with the idea of not exposing internal pointers to plugins
(e.g. we don't pass a CPUState *, only an opaque handle) so I'm OK
with returning a dup'ed string here.

(snip)
> That said in another
> thread Peter was uncomfortable about exposing this piece of information
> to plugins. Maybe we should only expose something based on the optional
> -device foo,id=bar parameter?

I have no opinion on whether exposing this is a good idea. If it turns
out that it is, please have my

Reviewed-by: Emilio G. Cota <cota@braap.org>

Thanks,

		Emilio