Re: [PATCH] btrfs: initialize location to fix -Wmaybe-uninitialized in btrfs_lookup_dentry()

[Qu Wenruo <quwenruo.btrfs@gmx.com>]

在 2024/7/30 05:36, David Sterba 写道:
> Some arch + compiler combinations report a potentially unused variable
> location in btrfs_lookup_dentry(). This is a false alert as the variable
> is passed by value and always valid or there's an error. The compilers
> cannot probably reason about that although btrfs_inode_by_name() is in
> the same file.
>
>     >  + /kisskb/src/fs/btrfs/inode.c: error: 'location.objectid' may be used
>     +uninitialized in this function [-Werror=maybe-uninitialized]:  => 5603:9
>     >  + /kisskb/src/fs/btrfs/inode.c: error: 'location.type' may be used
>     +uninitialized in this function [-Werror=maybe-uninitialized]:  => 5674:5
>
>     m68k-gcc8/m68k-allmodconfig
>     mips-gcc8/mips-allmodconfig
>     powerpc-gcc5/powerpc-all{mod,yes}config
>     powerpc-gcc5/ppc64_defconfig
>
> Initialize it to zero, this should fix the warnings and won't change the
> behaviour as btrfs_inode_by_name() accepts only a root or inode item
> types, otherwise returns an error.
>
> Reported-by: Geert Uytterhoeven <geert@linux-m68k.org>
> Link: https://lore.kernel.org/linux-btrfs/bd4e9928-17b3-9257-8ba7-6b7f9bbb639a@linux-m68k.org/
> Signed-off-by: David Sterba <dsterba@suse.com>

Reviewed-by: Qu Wenruo <wqu@suse.com>

Although I hate to update our code for bad compilers, I guess it's
unavoidable anyway.

Thanks,
Qu
> ---
>   fs/btrfs/inode.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
> index 32010127710d..333b0e8587a2 100644
> --- a/fs/btrfs/inode.c
> +++ b/fs/btrfs/inode.c
> @@ -5667,7 +5667,7 @@ struct inode *btrfs_lookup_dentry(struct inode *dir, struct dentry *dentry)
>   	struct inode *inode;
>   	struct btrfs_root *root = BTRFS_I(dir)->root;
>   	struct btrfs_root *sub_root = root;
> -	struct btrfs_key location;
> +	struct btrfs_key location = { 0 };
>   	u8 di_type = 0;
>   	int ret = 0;
>