linux-kernel - Re: [PATCH] fs: tree-checker: fix missing brace warning for old compilers

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Date:   Sat, 3 Oct 2020 11:04:29 +0300
From:   Nikolay Borisov <nborisov@...e.com>
To:     Pujin Shi <shipujin.t@...il.com>, Chris Mason <clm@...com>,
        Josef Bacik <josef@...icpanda.com>,
        David Sterba <dsterba@...e.com>
Cc:     Qu Wenruo <wqu@...e.com>, linux-btrfs@...r.kernel.org,
        linux-kernel@...r.kernel.org, hankinsea@...il.com
Subject: Re: [PATCH] fs: tree-checker: fix missing brace warning for old
 compilers



On 3.10.20 г. 3:11 ч., Pujin Shi wrote:
> For older versions of gcc, the array = {0}; will cause warnings:
> 
> fs/btrfs/tree-checker.c: In function 'check_root_item':
> fs/btrfs/tree-checker.c:1038:9: warning: missing braces around initializer [-Wmissing-braces]
>   struct btrfs_root_item ri = { 0 };
>          ^
> fs/btrfs/tree-checker.c:1038:9: warning: (near initialization for 'ri.inode') [-Wmissing-braces]
> 
> 1 warnings generated
> 
> Fixes: 443b313c7ff8 ("btrfs: tree-checker: fix false alert caused by legacy btrfs root item")
> Signed-off-by: Pujin Shi <shipujin.t@...il.com>

This is a compiler artifact, please see:
http://www.ex-parrot.com/~chris/random/initialise.html

ALso having an empty initialization list like = {} while valid for gcc
is actually invalid according to the official standard. Check ISO C
Standard section 6.7.9 for the correct syntax of initializer-list.

IOW - NAK.

> ---
>  fs/btrfs/tree-checker.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/fs/btrfs/tree-checker.c b/fs/btrfs/tree-checker.c
> index f0ffd5ee77bd..5028b3af308c 100644
> --- a/fs/btrfs/tree-checker.c
> +++ b/fs/btrfs/tree-checker.c
> @@ -1035,7 +1035,7 @@ static int check_root_item(struct extent_buffer *leaf, struct btrfs_key *key,
>  			   int slot)
>  {
>  	struct btrfs_fs_info *fs_info = leaf->fs_info;
> -	struct btrfs_root_item ri = { 0 };
> +	struct btrfs_root_item ri = {};
>  	const u64 valid_root_flags = BTRFS_ROOT_SUBVOL_RDONLY |
>  				     BTRFS_ROOT_SUBVOL_DEAD;
>  	int ret;
>