linux-kernel - Re: [PATCH] fs/exofs: Remove ignored _

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Date:   Mon, 1 Oct 2018 15:47:10 -0700
From:   Nick Desaulniers <ndesaulniers@...gle.com>
To:     Nathan Chancellor <natechancellor@...il.com>
Cc:     ooo@...ctrozaur.com, Andrew Morton <akpm@...ux-foundation.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] fs/exofs: Remove ignored __weak attribute

On Sun, Sep 30, 2018 at 1:51 PM Nathan Chancellor
<natechancellor@...il.com> wrote:
>
> Clang warns that the __weak attribute is going to be ignored on
> g_attr_inode_data because it's not in the correct location (needs to be
> after the type).
>
> In file included from fs/exofs/dir.c:35:
> In file included from fs/exofs/exofs.h:41:
> fs/exofs/common.h:186:21: warning: 'weak' attribute only applies to
> variables, functions, and classes [-Wignored-attributes]
> static const struct __weak osd_attr g_attr_inode_data = ATTR_DEF(
>                     ^
>
> Turns out that GCC ignores the attribute too albeit silently because
> moving the attribute after either osd_attr or g_attr_inode_data like
> all other uses of __weak on variables in the kernel causes a build
> error on both GCC and Clang because static variables cannot be weak
> since weak definitions rely on not having internal linkage:
>
> In file included from fs/exofs/namei.c:34:
> In file included from fs/exofs/exofs.h:41:
> fs/exofs/common.h:186:30: error: weak declaration cannot have internal
> linkage
> static const struct osd_attr __weak g_attr_inode_data = ATTR_DEF(
>                              ^
>
> Just remove the attribute because it hasn't been correct since the
> initial addition of this file in commit b14f8ab28449 ("exofs: Kbuild,
> Headers and osd utils").
>
> Reported-by: Nick Desaulniers <ndesaulniers@...gle.com>
> Reviewed-by: Nick Desaulniers <ndesaulniers@...gle.com>
> Signed-off-by: Nathan Chancellor <natechancellor@...il.com>
> ---
>  fs/exofs/common.h | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/fs/exofs/common.h b/fs/exofs/common.h
> index 7d88ef566213..45da96a1528d 100644
> --- a/fs/exofs/common.h
> +++ b/fs/exofs/common.h
> @@ -183,7 +183,7 @@ struct exofs_fcb {
>  #define EXOFS_INO_ATTR_SIZE    sizeof(struct exofs_fcb)
>
>  /* This is the Attribute the fcb is stored in */
> -static const struct __weak osd_attr g_attr_inode_data = ATTR_DEF(
> +static const struct osd_attr g_attr_inode_data = ATTR_DEF(
>         EXOFS_APAGE_FS_DATA,
>         EXOFS_ATTR_INODE_DATA,
>         EXOFS_INO_ATTR_SIZE);
> --
> 2.19.0
>

LGTM, thank you for sending, Nathan.

-- 
Thanks,
~Nick Desaulniers