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Re: [PATCH] Fix readdir_r with long file names
- From: Florian Weimer <fweimer at redhat dot com>
- To: Paul Eggert <eggert at cs dot ucla dot edu>, "Michael Kerrisk (man-pages)" <mtk dot manpages at gmail dot com>, Siddhesh Poyarekar <siddhesh at redhat dot com>
- Cc: Rich Felker <dalias at aerifal dot cx>, "Carlos O'Donell" <carlos at redhat dot com>, KOSAKI Motohiro <kosaki dot motohiro at gmail dot com>, libc-alpha <libc-alpha at sourceware dot org>, Roland McGrath <roland at hack dot frob dot com>, linux-man <linux-man at vger dot kernel dot org>
- Date: Tue, 1 Mar 2016 23:16:10 +0100
- Subject: Re: [PATCH] Fix readdir_r with long file names
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On 03/01/2016 10:20 PM, Paul Eggert wrote:
> On 03/01/2016 12:27 PM, Florian Weimer wrote:
>> We
>> should implement compiler support for this wart: inhibit optimizations
>> (I think there are already special cases for length-0 and length-1
>> arrays at the end, so it's not totally without precedent), and warn
>> about sizeof (struct dirent) and using it as a (non-pointer) declarator.
>
> Why not use a flexible array member for this?
For which part, and how exactly?
You can't put a flexible array member into a transparent union.
> Sure, that assumes C99,
> but flexible array members are pretty much universally supported now
> (and we can fall back on the current layout for pre-C99 compilers). This
> would work better with modern compilers that treat small arrays with
> more respect than traditional C compilers did. And as I understand
> things, it would conform to POSIX (and if I'm wrong, POSIX should get
> fixed....).
If you mean to add some zero-width padding member at the end of the
struct, after the d_name member, then I'm worried that makes overrunning
the d_name array member even more undefined than it already is. :)
> For what it's worth, portable code cannot copy struct dirent values
> anyway, as this loses file names in operating systems like Solaris where
> d_name has size 1.
Interesting. I feel slightly better now about having this overrunning
d_name member.
Florian