linux-kernel - Re: [PATCH] uio.c: Fix warning: 'ret' might be used uninitialized

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Message-Id: <201211291836.59358.vitas@nppfactor.kiev.ua>
Date:	Thu, 29 Nov 2012 18:36:59 +0200
From:	Vitalii Demianets <vitas@...factor.kiev.ua>
To:	Tux9 <tuxding@...il.com>
Cc:	"Hans J. Koch" <hjk@...sjkoch.de>, linux-kernel@...r.kernel.org,
	"Greg Kroah-Hartman" <gregkh@...uxfoundation.org>
Subject: Re: [PATCH] uio.c: Fix warning: 'ret' might be used uninitialized

> On Thursday 29 November 2012 18:05:27 Tux9 wrote:
> > Hans, I think there are something wrong in your patch, while Vitalii's
> > is right. The variable "ret" is reused in line 292 and line 295, so
> > the value of "ret" would be overridden (if it goto err_map in line 284
> > when mi>=1).
>
> Actually, both patches do exactly the same thing. Hans's patch establishes
> default value for the ret for all those "other" cases when ret is not
> explicitly overridden. My patch explicitly enumerates all those "other"
> cases in more wordily manner.
>

Oops, disregard this. After looking at it more thoroughly I got your point.
You are right, ret is overridden at first iteration (mi == 0), so Hans's 
approach does not work.
I must do more thinking before replying in a hurry.

> > On Wed, Nov 28, 2012 at 10:05 PM, Hans J. Koch <hjk@...sjkoch.de> wrote:
> > > On Wed, Nov 28, 2012 at 10:58:32AM +0200, Vitalii Demianets wrote:
> > >> On Wednesday 28 November 2012 00:43:41 Hans J. Koch wrote:
> > >> > Thanks, good catch, but why don't you simply do this:
> > >>
> > >> Just a matter of personal preference.
> > >
> > > Your patch: 1 files changed, 12 insertions(+), 4 deletions(-)
> > > My patch: 1 files changed, 1 insertions(+), 1 deletions(-)
> > >
> > > Both achieve exactly the same. That's not a matter of personal
> > > preference, that's the difference between a working solution and
> > > a good solution. In the kernel, we want the latter.
> > >
> > >> As a maintainer you can apply either
> > >> patch you want. I guess you would prefer your approach and I have no
> > >> objections to that :)
> > >
> > > That's not the right kind of comment. Don't make it a habit.
> > >
> > > Thanks,
> > > Hans
> > >
> > >> > >From 228445996bb75a44d16b6237eca6a0916d9b2d7e Mon Sep 17 00:00:00
> > >> > > 2001
> > >> >
> > >> > From: "Hans J. Koch" <hjk@...sjkoch.de>
> > >> > Date: Tue, 27 Nov 2012 23:38:00 +0100
> > >> > Subject: [PATCH] uio: Fix warning: 'ret' might be used uninitialized
> > >> >
> > >> > In two cases, the return value variable "ret" can be undefined.
> > >> >
> > >> > Signed-off-by: Hans J. Koch <hjk@...sjkoch.de>
> > >> > ---
> > >> >  drivers/uio/uio.c |    2 +-
> > >> >  1 files changed, 1 insertions(+), 1 deletions(-)
> > >> >
> > >> > diff --git a/drivers/uio/uio.c b/drivers/uio/uio.c
> > >> > index 5110f36..fc60e35 100644
> > >> > --- a/drivers/uio/uio.c
> > >> > +++ b/drivers/uio/uio.c
> > >> > @@ -263,7 +263,7 @@ static struct class uio_class = {
> > >> >   */
> > >> >  static int uio_dev_add_attributes(struct uio_device *idev)
> > >> >  {
> > >> > -   int ret;
> > >> > +   int ret = -ENOMEM;
> > >> >     int mi, pi;
> > >> >     int map_found = 0;
> > >> >     int portio_found = 0;
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