Re: d_off field in struct dirent and 32-on-64 emulation

From: Florian Weimer
Date: Thu Dec 27 2018 - 13:09:26 EST

* 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:

>> There is another annoying aspect: The standards expose d_off through
>> the telldir function, and that returns long int on all architectures
>> (not off_t, so unchanged by _FILE_OFFSET_BITS). That's mostly a
>> userspace issue and thus needing different steps to resolve (possibly
>> standards action).