This is the mail archive of the
libc-alpha@sourceware.org
mailing list for the glibc project.
Re: d_off field in struct dirent and 32-on-64 emulation
- From: Florian Weimer <fw at deneb dot enyo dot de>
- To: Adhemerval Zanella <adhemerval dot zanella at linaro dot org>
- Cc: linux-fsdevel at vger dot kernel dot org, linux-api at vger dot kernel dot org, linux-ext4 at vger dot kernel dot org, linux-kernel at vger dot kernel dot org, v9fs-developer at lists dot sourceforge dot net, libc-alpha at sourceware dot org, qemu-devel at nongnu dot org, ericvh at gmail dot com, lucho at ionkov dot net, hpa at zytor dot com, arnd at arndb dot de
- Date: Fri, 28 Dec 2018 13:01:43 +0100
- Subject: Re: d_off field in struct dirent and 32-on-64 emulation
- References: <87bm56vqg4.fsf@mid.deneb.enyo.de> <957967d7-5717-8ada-fb30-dfdf19898b6b@linaro.org> <87pntmu9iw.fsf@mid.deneb.enyo.de> <ae0530c9-5c46-5560-9734-1eacaf173b8d@linaro.org> <87k1jtvp8u.fsf@mid.deneb.enyo.de>
* Florian Weimer:
> * Adhemerval Zanella:
>
>> On 27/12/2018 16:09, Florian Weimer wrote:
>>> * Adhemerval Zanella:
>>>
>>>> Also for glibc standpoint, although reverting it back to use getdents
>>>> syscall for non-LFS mode might fix this issue for architectures that
>>>> provides non-LFS getdents syscall it won't be a fix for architectures
>>>> that still provides off_t different than off64_t *and* only provides
>>>> getdents64 syscall.
>>>>
>>>> Currently we only have nios2 and csky (unfortunately). But since generic
>>>> definition for off_t and off64_t still assumes non-LFS support, all new
>>>> 32-bits ports potentially might carry the issue.
>>>
>>> For csky, we could still change the type of the non-standard d_off
>>> field to long long int. This way, only telldir would have to fail
>>> when truncation is necessary, as mentioned below:
>>
>> I think it makes no sense to continue making non-LFS as default for
>> newer 32 bits ports, the support will be emulated with LFS syscalls.
>
> Sorry, I don't see how this matters. seekdir and telldir are NOT
> affected by LFS.
Ah, right. If struct dirent is 64-bit only, then the d_off member
will be 64 bits as well. But it is unclear whether you can use that
with lseek (probably yes, in its 64-bit variant), and it's unlikely
it's going to work with seekdir because of the POSIX-required long int
type.