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SubjectRe: [PATCH] shm: Remove silly double assignment
On Wed, Jun 11, 2008 at 03:45:06AM -0700, Andrew Morton wrote:
> On Tue, 10 Jun 2008 08:53:39 -0400 Neil Horman <nhorman@tuxdriver.com> wrote:
>
> > Found a silly double assignment of err is do_shmat. Silly, but good to clean up
> > the useless code.
> >
> > Signed-off-by: Neil Horman <nhorman@tuxdriver.com>
> >
> > diff --git a/ipc/shm.c b/ipc/shm.c
> > index 554429a..d05f6b5 100644
> > --- a/ipc/shm.c
> > +++ b/ipc/shm.c
> > @@ -894,8 +894,6 @@ long do_shmat(int shmid, char __user *shmaddr, int shmflg, ulong *raddr)
> > if (!sfd)
> > goto out_put_dentry;
> >
> > - err = -ENOMEM;
> > -
> > file = alloc_file(path.mnt, path.dentry, f_mode, &shm_file_operations);
> > if (!file)
> > goto out_free;
>
> Not silly, really. Look:
>
> err = -ENOMEM;
> if (expr1)
> goto out;
>
> err = -ENOMEM;
> if (expr2)
> goto out;
>
> each of these two units is a separate, self-contained clause. Removing
> the second assignment to `err' breaks that separation and will make one
> clause undesirably dependent upon the other.
yes, I see that keeping the second assignment lets you insert code in the middle
without having up to update afterwards. I just don't think the redundant
assignment is worth keeping just for that purpose.


>
> Example: if someone later comes up and does
>
> err = -ENOMEM;
> if (expr1)
> goto out;
>
> + er = -EINVAL;
> + if (expr3)
> + goto out;
>
> if (expr2)
> goto out;
>
> then whoops, it broke.
>
Yes, but that would be the fault of the subsequent patch, and if they couldn't
see that problem, I fear that a double assignment isn't going to help them much.

> The compiler should optimise away the second assignment anyway.
Agreed, its really not a big deal. If its not worth it, its fine with me. I
was just being janitorial, and thought this looked rather redundant.

Best
Neil

--
/****************************************************
* Neil Horman <nhorman@tuxdriver.com>
* Software Engineer, Red Hat
****************************************************/


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