linux-kernel - Re: [PATCH net-next][resend v1 1/1] netlink: Don't use int as bool in netlink_update_socket

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Message-ID: <20230711122012.GR41919@unreal>
Date:   Tue, 11 Jul 2023 15:20:12 +0300
From:   Leon Romanovsky <leon@...nel.org>
To:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Cc:     Paolo Abeni <pabeni@...hat.com>, Jakub Kicinski <kuba@...nel.org>,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>
Subject: Re: [PATCH net-next][resend v1 1/1] netlink: Don't use int as bool
 in netlink_update_socket_mc()

On Tue, Jul 11, 2023 at 01:54:18PM +0300, Andy Shevchenko wrote:
> On Tue, Jul 11, 2023 at 12:21:12PM +0200, Paolo Abeni wrote:
> > On Tue, 2023-07-11 at 09:33 +0300, Leon Romanovsky wrote:
> > > On Mon, Jul 10, 2023 at 01:06:24PM +0300, Andy Shevchenko wrote:
> > > > The bit operations take boolean parameter and return also boolean
> > > > (in test_bit()-like cases). Don't threat booleans as integers when
> > > > it's not needed.
> > > > 
> > > > Signed-off-by: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
> > > > ---
> > > >  net/netlink/af_netlink.c | 7 ++++---
> > > >  1 file changed, 4 insertions(+), 3 deletions(-)
> > > > 
> > > > diff --git a/net/netlink/af_netlink.c b/net/netlink/af_netlink.c
> > > > index 383631873748..d81e7a43944c 100644
> > > > --- a/net/netlink/af_netlink.c
> > > > +++ b/net/netlink/af_netlink.c
> > > > @@ -1623,9 +1623,10 @@ EXPORT_SYMBOL(netlink_set_err);
> > > >  /* must be called with netlink table grabbed */
> > > >  static void netlink_update_socket_mc(struct netlink_sock *nlk,
> > > >  				     unsigned int group,
> > > > -				     int is_new)
> > > > +				     bool new)
> > > >  {
> > > > -	int old, new = !!is_new, subscriptions;
> > > > +	int subscriptions;
> > > > +	bool old;
> > > >  
> > > >  	old = test_bit(group - 1, nlk->groups);
> > > >  	subscriptions = nlk->subscriptions - old + new;
> > > 
> > > So what is the outcome of "int - bool + bool" in the line above?
> 
> The same as with int - int [0 .. 1] + int [0 .. 1].

No, it is not. bool is defined as _Bool C99 type, so strictly speaking
you are mixing types int - _Bool + _Bool.

Thanks

> 
> Note, the code _already_ uses boolean as integers.
> 
> > FTR, I agree with Leon, the old code is more readable to me/I don't see
> > a practical gain with this change.
> 
> This change does not change the status quo. The code uses booleans as integers
> already (in the callers).
> 
> As I mentioned earlier, the purity of the code (converting booleans to integers
> beforehand) adds unneeded churn and with this change code becomes cleaner at
> least for the (existing) callers.
> 
> -- 
> With Best Regards,
> Andy Shevchenko
> 
>