[Spice-devel] [PATCH 5/9] server: dispatcher_init/dispatcher_new

[Frediano Ziglio]

> 
> On Wed, Oct 21, 2015 at 08:37:25AM -0400, Frediano Ziglio wrote:
> > 
> > > 
> > > From: Marc-André Lureau <marcandre.lureau at gmail.com>
> > > 
> > > ---
> > >  server/red_dispatcher.c | 6 ++++--
> > >  server/red_dispatcher.h | 2 +-
> > >  server/reds.c           | 2 +-
> > >  3 files changed, 6 insertions(+), 4 deletions(-)
> > > 
> > > diff --git a/server/red_dispatcher.c b/server/red_dispatcher.c
> > > index 0bc853d..c43da7d 100644
> > > --- a/server/red_dispatcher.c
> > > +++ b/server/red_dispatcher.c
> > > @@ -1060,7 +1060,7 @@ static RedChannel
> > > *red_dispatcher_cursor_channel_create(RedDispatcher *dispatche
> > >      return cursor_channel;
> > >  }
> > >  
> > > -void red_dispatcher_init(QXLInstance *qxl)
> > > +RedDispatcher *red_dispatcher_new(QXLInstance *qxl)
> > >  {
> > >      RedDispatcher *red_dispatcher;
> > >      WorkerInitData init_data;
> > > @@ -1069,7 +1069,7 @@ void red_dispatcher_init(QXLInstance *qxl)
> > >      RedChannel *cursor_channel;
> > >      ClientCbs client_cbs = { NULL, };
> > >  
> > > -    spice_return_if_fail(qxl->st->dispatcher == NULL);
> > > +    spice_return_val_if_fail(qxl->st->dispatcher == NULL, NULL);
> > > 
> > 
> > This is just going to leak the old dispatcher if already set, see below.
> > This should be an assert.
> 
> If spice_return_val_if_fail() are anything like g_return_val_if_fail(),
> they usually mean "programming error, anything may happen from this
> point". If there's only a minor leak when this occurs, this is fair game
> imo, and better than an assert().
> 
> Christophe
> 

Usually I like to think about contracts

  void red_dispatcher_init(QXLInstance *qxl)

says "initialize a dispatcher given a QXLInstance object" while

  RedDispatcher *red_dispatcher_new(QXLInstance *qxl)

says "create a new dispatcher given this QXLInstance object".

With first contract the check make more sense while in the last one one
could argue that the function should just create a new object. The check
assume that there will be a relationship between the instance qxl and the
created dispatcher which is made clear in the caller setting qxl->st->dispatcher
so why should not be this assignment inside red_dispatcher_new if they both
have this knowledge?

This assume a 1-to-1 relationship between the dispatcher and the worker
which for me would prefer a red_dispatcher_init than a red_dispatcher_new.

Frediano