lkml.org 
[lkml]   [2014]   [May]   [29]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH] fs: ocfs2: move_extents.c: Fix to remove null pointer checks that could never happen
On Thu, May 29, 2014 at 02:03:37PM -0700, Andrew Morton wrote:
> On Tue, 27 May 2014 22:23:51 +0200 Rickard Strandqvist <rickard_strandqvist@spectrumdigital.se> wrote:
>
> > Removal of null pointer checks that could never happen
>
> How do you know it never happens?
>
> > --- a/fs/ocfs2/move_extents.c
> > +++ b/fs/ocfs2/move_extents.c
> > @@ -904,9 +904,6 @@ static int ocfs2_move_extents(struct ocfs2_move_extents_context *context)
> > struct buffer_head *di_bh = NULL;
> > struct ocfs2_super *osb = OCFS2_SB(inode->i_sb);
> >
> > - if (!inode)
> > - return -ENOENT;
> > -
>
> If it's due to assuming that the previous statement would have oopsed
> then that is mistaken. Is is sometimes the case that gcc will move the
> evaluation of inode->i_sb to after the test, so this function can be
> passed NULL and it will not oops.

'sometimes' ?

You have a lot more faith in gcc than I do. What happens if we decide to
switch to llvm one day ? Can we guarantee every compiler will implement
the same magic ? This seems fragile as hell to me.

Dave



\
 
 \ /
  Last update: 2014-05-30 00:01    [W:0.908 / U:0.088 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site