Re: [PATCH] zfs: fix compilation failure with clang due to alignment

[Vladimir 'φ-coder/phcoder' Serbinenko]

On 03.07.2015 21:05, Andrei Borzenkov wrote:
> I do not claim I understand why clang complains, but this patch does
> fix it.
> 
> fs/xfs.c:452:25: error: cast from 'struct grub_xfs_btree_node *' to
>       'grub_uint64_t *' (aka 'unsigned long long *') increases required
>       alignment from 1 to 8 [-Werror,-Wcast-align]
>   grub_uint64_t *keys = (grub_uint64_t *)(leaf + 1);
>                         ^~~~~~~~~~~~~~~~~~~~~~~~~~~
> 1 error generated.
> 
> ---
> 
> Jan, do you have any idea what's wrong and whether this is proper fix?
> Or should I raise it with clang?
> 
>  grub-core/fs/xfs.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/grub-core/fs/xfs.c b/grub-core/fs/xfs.c
> index 7249291..ea8cf7e 100644
> --- a/grub-core/fs/xfs.c
> +++ b/grub-core/fs/xfs.c
> @@ -445,14 +445,14 @@ grub_xfs_next_de(struct grub_xfs_data *data, struct 
> grub_xfs_dir2_entry *de)
>    return (struct grub_xfs_dir2_entry *)(((char *)de) + ALIGN_UP(size, 8));
>  }
>  
> -static grub_uint64_t *
> +static void *
>  grub_xfs_btree_keys(struct grub_xfs_data *data,
>                   struct grub_xfs_btree_node *leaf)
>  {
> -  grub_uint64_t *keys = (grub_uint64_t *)(leaf + 1);
> +  char *keys = (char *)leaf + sizeof (*leaf);
>  
>    if (data->hascrc)
> -    keys += 6;       /* skip crc, uuid, ... */
> +    keys += 6 * sizeof (grub_uint64_t);      /* skip crc, uuid, ... */
>    return keys;
>  }
>  
This would only hide the problem behind void*. Leif's patch solves the
problem. Another possibility is to analyze if packed is really required
but most likely it is.
>

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