From mboxrd@z Thu Jan  1 00:00:00 1970
From: Stephen Hemminger <stephen@networkplumber.org>
Subject: Re: [PATCH iproute2 v2] json_print: Fix hidden 64-bit type
 promotion
Date: Wed, 25 Apr 2018 08:12:10 -0700
Message-ID: <20180425081210.41846761@xeon-e3>
References: <20180329192220.30101-1-ldir@darbyshire-bryant.me.uk>
        <20180425143022.6986-1-toke@toke.dk>
        <20180425075527.680f34fc@xeon-e3>
        <87bme75o5r.fsf@toke.dk>
Mime-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: quoted-printable
Cc: netdev@vger.kernel.org,
        Kevin Darbyshire-Bryant <ldir@darbyshire-bryant.me.uk>
To: Toke =?UTF-8?B?SMO4aWxhbmQtSsO4cmdlbnNlbg==?= <toke@toke.dk>
Return-path: <netdev-owner@vger.kernel.org>
Received: from mail-pf0-f176.google.com ([209.85.192.176]:39406 "EHLO
        mail-pf0-f176.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org
        with ESMTP id S1755001AbeDYPMN (ORCPT
        <rfc822;netdev@vger.kernel.org>); Wed, 25 Apr 2018 11:12:13 -0400
Received: by mail-pf0-f176.google.com with SMTP id z9so15490192pfe.6
        for <netdev@vger.kernel.org>; Wed, 25 Apr 2018 08:12:13 -0700 (PDT)
In-Reply-To: <87bme75o5r.fsf@toke.dk>
Sender: netdev-owner@vger.kernel.org
List-ID: <netdev.vger.kernel.org>

On Wed, 25 Apr 2018 16:57:52 +0200
Toke H=C3=B8iland-J=C3=B8rgensen <toke@toke.dk> wrote:

> Stephen Hemminger <stephen@networkplumber.org> writes:
>=20
> > On Wed, 25 Apr 2018 16:30:22 +0200
> > Toke H=C3=B8iland-J=C3=B8rgensen <toke@toke.dk> wrote:
> > =20
> >> print_uint() will silently promote its variable type to uint64_t, but =
there
> >> is nothing that ensures that the format string specifier passed along =
with
> >> it fits (and the function name suggest to pass "%u").
> >>=20
> >> Fix this by changing print_uint() to use a native 'unsigned int' type,=
 and
> >> introduce a separate print_u64() function for printing 64-bit values. =
All
> >> call sites that were actually printing 64-bit values using print_uint(=
) are
> >> converted to use print_u64() instead.
> >>=20
> >> Since print_int() was already using native int types, just add a
> >> print_s64() to match, but don't convert any call sites.
> >>=20
> >> Cc: Kevin Darbyshire-Bryant <ldir@darbyshire-bryant.me.uk>
> >> Signed-off-by: Toke H=C3=B8iland-J=C3=B8rgensen <toke@toke.dk> =20
> >
> > Yes, this makes sense. Maybe there should be a print_luint for
> > consistency. =20
>=20
> I just realised I missed a few call sites, so I'll resend. Should I
> call the new function print_luint() instead of print_u64()?

Ideally, there would be both functions, and use based on what is being prin=
ted.

> > Also, I tried (in vain) to make a version that allows GCC to check the
> > format string.  But it was a struggle and just gave up. =20
>=20
> Yeah, no idea how to do this either...

Maybe some magic smatch or multi-line regex it would be possible to
find all instances of print_uint, then look at format string of each and se=
e if there is
a single %u.  Some added complexity since some places only print json and d=
on't care
and pass NULL for format.