linux-kernel - Re: [PATCH] vfs: workaround gcc <4.6 build error in link_path

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Message-ID: <20140916173951.GX7996@ZenIV.linux.org.uk>
Date:	Tue, 16 Sep 2014 18:39:51 +0100
From:	Al Viro <viro@...IV.linux.org.uk>
To:	James Hogan <james.hogan@...tec.com>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	linux-kernel@...r.kernel.org,
	Geert Uytterhoeven <geert@...ux-m68k.org>,
	linux-fsdevel@...r.kernel.org, linux-metag@...r.kernel.org
Subject: Re: [PATCH] vfs: workaround gcc <4.6 build error in link_path_walk()

On Tue, Sep 16, 2014 at 01:07:35PM +0100, James Hogan wrote:
> Commit d6bb3e9075bb (vfs: simplify and shrink stack frame of
> link_path_walk()) introduced build problems with GCC versions older than
> 4.6 due to the initialisation of a member of an anonymous union in
> struct qstr without enclosing braces.
> 
> This hits GCC bug 10676 [1] (which was fixed in GCC 4.6 by [2]), and
> causes the following build error:
>   fs/namei.c: In function 'link_path_walk':
>   fs/namei.c:1778: error: unknown field 'hash_len' specified in initializer
> 
> This is worked around by adding explicit braces.

IOW, the same thing QSTR_INIT is doing...  BTW, after looking at the commit
in question, what the hell was this
+                               name = this.name;
in link_path_walk() about?  Granted, none of the ->d_hash() instances in
the tree reassign qstr->name, and out-of-tree ones are unlikely to do it
either, so it's harmless but... why bother rereading this.name at all?
Linus?
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