Re: [PATCH v3 1/2] include/fcntl.h: Define O_IGNORE_CTTY

[Sergey Bugaev]

Hello,

On Mon, Jun 12, 2023 at 9:56 PM Adhemerval Zanella Netto
<adhemerval.zanella@linaro.org> wrote:
> > Do you think the Linux port should define O_IGNORE_CTTY to O_NOCTTY
> > and not to 0?
>
> Hurd O_IGNORE_CTTY and Linux O_NOCTTY do not have the *exactly* semantic,
> so I think we should avoid change the internal open flags in this
> specific patch.

OK.

> We have the internal header file, to say 'include/fcntl.h', which is
> used when building glibc itself including the tests.  The internal-only
> header also includes the installed one, 'io/fcntl.h', which defines
> the ABI glibc provides.

Yes, that I understand.

> So to override a internal-only definition we have some options:
>
>   1. Override the file which is has precedence in the sysdeps selection
>      (which defines the -I at built time).  So if you add the file
>      "sysdeps/unix/sysv/linux/include/fcntl.h'., it would be included
>      instead of 'include/fcntl.h'.

Oh cool, I didn't realize it was possible to nest include/ under
sysdeps/, thank you! I thought there was only the top-level include/
directory, but now I see that there are more, including even a few
Mach/Hurd specific ones.

>   2. Add per-system file that is included in the generic 'include/fcntl.h',
>      for instance fcntl-system.h or something like that.  On then add
>      a generic definition on sysdep/generic/ with the expected value
>      and override it on any sysdep folder that requires it.

Is there already an example of such a header file? I can't find any
files in any include/ directory matching either *sysdep* or *system*.

> I tend to see the second options as a slight simpler one.

The first option sounds simpler to me.

Should it be sysdeps/unix/sysv/linux/include/fcntl.h or
sysdeps/generic/include/fcntl.h? If it's the latter, I'd have to
create a sysdeps/hurd/include/fcntl.h that does not (re)define
O_IGNORE_CTTY (right?).

> > But this brings me to the more specific question: the headers to be
> > installed are also found using vpath during 'make install', right? How
> > would this work, will Make somehow know to not install this
> > sysdeps/unix/sysv/linux/fcntl.h file that you're proposing, and keep
> > installing io/fcntl.h?
>
> Afaiu there is no need to install any new header for this, this is an
> internal only definition to use on open call within glibc.

Yes, this is my point: you were suggesting that I add
sysdeps/unix/sysv/linux/fcntl.h (notice no /include/ in the middle),
which -- I'm not sure whether it would get installed by the build
system (instead of io/fcntl.h) or not. I want it to *not* get
installed. The option with /include/ in the middle that you're
suggesting now should take care of that.

Sergey