Re: env: follow up on argv0 setting feature

[Pádraig Brady]

On 20/03/2024 23:19, Pádraig Brady wrote:
> On 13/03/2024 10:19, Matheus Afonso Martins Moreira wrote:
> > About a year ago, I posted an env feature request on this list:
> > the ability to set the value of argv[0].
> >
> > https://lists.gnu.org/archive/html/coreutils/2023-03/msg00002.html
> >
> > I also sent a patch:
> >
> > https://lists.gnu.org/archive/html/coreutils/2023-03/msg00003.html
> >
> > After some discussion, I was informed it was under consideration:
> >
> > https://lists.gnu.org/archive/html/coreutils/2023-03/msg00012.html
> >
> > > We're still considering and will adjust as needed.
> >
> > I waited a while and eventually sent an email about it:
> >
> > https://lists.gnu.org/archive/html/coreutils/2023-08/msg00059.html
> >
> > The maintainer noted that they expected this feature to be included
> > in the next release which would be focused on features:
> >
> > https://lists.gnu.org/archive/html/coreutils/2023-08/msg00060.html
> >
> > > The next release will focus on new features, and this
> > > will be considered. I expect this feature will be included.
> >
> > Since then I've been tracking commits to the coreutils master branch
> > but it appears the feature has not landed yet.
> >
> > What happened? Was it rejected?
>
> Thanks for your patience.
> I've attached an implementation for --argv0
> which I intend to apply for the impending release.
> Note this can accept empty and NULL values,
> and so now gives env full control of the args it passes on.

In testing this on a newer Linux kernel I see that argv[0] == NULL
is converted to an empty string instead.
That was one of the proposals at https://lwn.net/Articles/882799/
and I see it was implemented on kernels >= 5.18:
https://github.com/torvalds/linux/commit/dcd46d89

So in retrospect it's probably not worth supporting a NULL argv0,
as newer kernels won't pass it.  Also with a NULL argv0,
the kernel puts the environ array directly after the first NULL,
and so will discard any other params passed to env,
which would be confusing to users.

Version 2 attached, now makes --argv0 require an argument.

thanks,
Pádraig.

env--argv0.patch
Description: Text Data