2019-03-22 14:10:05

by Arnd Bergmann

Subject: [PATCH] btrfs: work around false-positive -Wsometimes-uninitialized warning

clang fails to see that the last 'else if() in btrfs_uuid_tree_add()
is always true, so 'eb' is always initialized correctly:

fs/btrfs/uuid-tree.c:129:13: error: variable 'eb' is used uninitialized whenever 'if' condition is false [-Werror,-Wsometimes-uninitialized]
} else if (ret < 0) {
^~~~~~~
fs/btrfs/uuid-tree.c:139:22: note: uninitialized use occurs here
write_extent_buffer(eb, &subid_le, offset, sizeof(subid_le));
^~
fs/btrfs/uuid-tree.c:129:9: note: remove the 'if' if its condition is always true
} else if (ret < 0) {
^~~~~~~~~~~~~
fs/btrfs/uuid-tree.c:90:26: note: initialize the variable 'eb' to silence this warning
struct extent_buffer *eb;
^
= NULL

Change it into a plain 'else' to shut up that warning.

Link: https://bugs.llvm.org/show_bug.cgi?id=41197
Signed-off-by: Arnd Bergmann <[email protected]>
---
fs/btrfs/uuid-tree.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/btrfs/uuid-tree.c b/fs/btrfs/uuid-tree.c
index 3b2ae342e649..c1cc9a5c0024 100644
--- a/fs/btrfs/uuid-tree.c
+++ b/fs/btrfs/uuid-tree.c
@@ -126,7 +126,7 @@ int btrfs_uuid_tree_add(struct btrfs_trans_handle *trans, u8 *uuid, u8 type,
slot = path->slots[0];
offset = btrfs_item_ptr_offset(eb, slot);
offset += btrfs_item_size_nr(eb, slot) - sizeof(subid_le);
- } else if (ret < 0) {
+ } else {
btrfs_warn(fs_info,
"insert uuid item failed %d (0x%016llx, 0x%016llx) type %u!",
ret, (unsigned long long)key.objectid,
--
2.20.0

2019-03-22 14:12:49

by Nikolay Borisov

Subject: Re: [PATCH] btrfs: work around false-positive -Wsometimes-uninitialized warning

On 22.03.19 г. 16:07 ч., Arnd Bergmann wrote:
> clang fails to see that the last 'else if() in btrfs_uuid_tree_add()
> is always true, so 'eb' is always initialized correctly:
>
> fs/btrfs/uuid-tree.c:129:13: error: variable 'eb' is used uninitialized whenever 'if' condition is false [-Werror,-Wsometimes-uninitialized]
> } else if (ret < 0) {
> ^~~~~~~
> fs/btrfs/uuid-tree.c:139:22: note: uninitialized use occurs here
> write_extent_buffer(eb, &subid_le, offset, sizeof(subid_le));
> ^~
> fs/btrfs/uuid-tree.c:129:9: note: remove the 'if' if its condition is always true
> } else if (ret < 0) {
> ^~~~~~~~~~~~~
> fs/btrfs/uuid-tree.c:90:26: note: initialize the variable 'eb' to silence this warning
> struct extent_buffer *eb;
> ^
> = NULL
>
> Change it into a plain 'else' to shut up that warning.
>
> Link: https://bugs.llvm.org/show_bug.cgi?id=41197
> Signed-off-by: Arnd Bergmann <[email protected]>

Such a patch has already been merged to misc-next:

f22898caa6a5 ("btrfs: Turn an 'else if' into an 'else' in
btrfs_uuid_tree_add")



> ---
> fs/btrfs/uuid-tree.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/fs/btrfs/uuid-tree.c b/fs/btrfs/uuid-tree.c
> index 3b2ae342e649..c1cc9a5c0024 100644
> --- a/fs/btrfs/uuid-tree.c
> +++ b/fs/btrfs/uuid-tree.c
> @@ -126,7 +126,7 @@ int btrfs_uuid_tree_add(struct btrfs_trans_handle *trans, u8 *uuid, u8 type,
> slot = path->slots[0];
> offset = btrfs_item_ptr_offset(eb, slot);
> offset += btrfs_item_size_nr(eb, slot) - sizeof(subid_le);
> - } else if (ret < 0) {
> + } else {
> btrfs_warn(fs_info,
> "insert uuid item failed %d (0x%016llx, 0x%016llx) type %u!",
> ret, (unsigned long long)key.objectid,
>

2019-03-22 14:26:10

by David Sterba

Subject: Re: [PATCH] btrfs: work around false-positive -Wsometimes-uninitialized warning

On Fri, Mar 22, 2019 at 04:11:52PM +0200, Nikolay Borisov wrote:
>
>
> On 22.03.19 г. 16:07 ч., Arnd Bergmann wrote:
> > clang fails to see that the last 'else if() in btrfs_uuid_tree_add()
> > is always true, so 'eb' is always initialized correctly:
> >
> > fs/btrfs/uuid-tree.c:129:13: error: variable 'eb' is used uninitialized whenever 'if' condition is false [-Werror,-Wsometimes-uninitialized]
> > } else if (ret < 0) {
> > ^~~~~~~
> > fs/btrfs/uuid-tree.c:139:22: note: uninitialized use occurs here
> > write_extent_buffer(eb, &subid_le, offset, sizeof(subid_le));
> > ^~
> > fs/btrfs/uuid-tree.c:129:9: note: remove the 'if' if its condition is always true
> > } else if (ret < 0) {
> > ^~~~~~~~~~~~~
> > fs/btrfs/uuid-tree.c:90:26: note: initialize the variable 'eb' to silence this warning
> > struct extent_buffer *eb;
> > ^
> > = NULL
> >
> > Change it into a plain 'else' to shut up that warning.
> >
> > Link: https://bugs.llvm.org/show_bug.cgi?id=41197
> > Signed-off-by: Arnd Bergmann <[email protected]>
>
> Such a patch has already been merged to misc-next:
>
> f22898caa6a5 ("btrfs: Turn an 'else if' into an 'else' in
> btrfs_uuid_tree_add")

I haven't updated for-next for a few days so the patch was not so
visible outside, will push an update today.