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

* Florian Weimer:

* Adhemerval Zanella:

quoted

On 27/12/2018 16:09, Florian Weimer wrote:

quoted

* Adhemerval Zanella:

quoted

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.

On 28/12/2018 10:01, Florian Weimer wrote:

* Florian Weimer:

quoted

* Adhemerval Zanella:

quoted

On 27/12/2018 16:09, Florian Weimer wrote:

quoted

* Adhemerval Zanella:

quoted

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.

I was referring to all other API that uses off_t as well (pread for
instance), where new ports will have non-LFS variants that will call
only LFS variants.