[Toybox] xargs "argument too long"

[enh]

(ping.)

On Mon, Jul 8, 2019 at 2:06 PM enh <enh at google.com> wrote:
>
> patch attached.
>
> i did check, in case we're crazy, and the kernel does do the right
> thing, there's no weird special case for these bytes in the kernel
> (this is linux; i didn't actually check a BSD kernel):
>
> /*
> * We must account for the size of all the argv and envp pointers to
> * the argv and envp strings, since they will also take up space in
> * the stack. They aren't stored until much later when we can't
> * signal to the parent that the child has run out of stack space.
> * Instead, calculate it here so it's possible to fail gracefully.
> */
> ptr_size = (bprm->argc + bprm->envc) * sizeof(void *);
> if (limit <= ptr_size)
> return -E2BIG;
>
> oddly the [Free]BSD xargs does count the space for the pointers for
> the common arguments given on the xargs command line, but not the
> pointers for the "extra" arguments from the input.
>
> On Sat, Jul 6, 2019 at 2:33 PM Rob Landley <rob at landley.net> wrote:
> >
> > On 7/2/19 1:26 PM, enh via Toybox wrote:
> > > so you'll not like this...
> >
> > You're right, I do not.
> >
> > > as far as i can tell, GNU xargs isn't counting those bytes. that's the
> > > only way i can make sense of the behavior when i add/subtract one from
> > > the -s argument...
> >
> > I want a kernel API to query how much environment space exec() can take. I
> > really, really do...
> >
> > > _seems_ like a GNU bug, but if no-one's cared/noticed all these years?
> > > plus the BSD xargs on macOS behaves the same as the GNU one, so
> > > there's widespread support for not counting the pointers...
> >
> > I am not currently capable of expressing my disgust in the ascii character set,
> > and am not up to trying to get thunderbird to understand emoji just now.
> >
> > Sigh, could you send me a git am patch? I really don't want to check that in
> > under my own name.
> >
> > Thanks,
> >
> > Rob