* Ingo Molnar <[email protected]> wrote:
> > However, I have to vehemently object to putting them in a wider scope
> > than is otherwise necessary. I agree that static variables should be
> > used sparsely if at all (there really are vary few uses of them that are
> > valid), but putting them in a larger scope screams "I'm used in more
> > than one function", and that is *not* a good thing.
>
> That's why we sometimes use the (imperfect) compromise to put them in front
> of
> that function, not at the top of the file.
>
> Look at the general balance of hardship: very little harm is done (it's not a
> big
> deal if a variable is only used in a single function) but having it with
> local
> variables can be _really_ harmful - for example i overlooked them when i
> reviewed
> this patch. I dont like important details obscured - i like them to be
> apparent.
> Again, this is something that some people can parse immediately on the visual
> level - me and many others cannot.
As an addendum, beyond my own bad experience with them, see below a recent
upstream
fix that shows the kinds of problems that overlooked function scope statics can
cause.
Ingo
------------->
>From 3cb50ddf97a0a1ca4c68bc12fa1e727a6b45fbf2 Mon Sep 17 00:00:00 2001
From: Al Viro <[email protected]>
Date: Mon, 20 Dec 2010 15:53:18 +0000
Subject: [PATCH] Fix btrfs b0rkage
Buggered-in: 76dda93c6ae2 ("Btrfs: add snapshot/subvolume destroy
ioctl")
Signed-off-by: Al Viro <[email protected]>
Acked-by: Chris Mason <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
---
fs/btrfs/export.c | 2 +-
1 files changed, 1 insertions(+), 1 deletions(-)
diff --git a/fs/btrfs/export.c b/fs/btrfs/export.c
index 6f04444..659f532 100644
--- a/fs/btrfs/export.c
+++ b/fs/btrfs/export.c
@@ -166,7 +166,7 @@ static struct dentry *btrfs_fh_to_dentry(struct super_block
*sb, struct fid *fh,
static struct dentry *btrfs_get_parent(struct dentry *child)
{
struct inode *dir = child->d_inode;
- static struct dentry *dentry;
+ struct dentry *dentry;
struct btrfs_root *root = BTRFS_I(dir)->root;
struct btrfs_path *path;
struct extent_buffer *leaf;
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