[Rd] Rscript -e EXPR fails to launch if stdin is closed

[Henrik Bengtsson]

Thank you Peter for the quick fix.  Will this make it into R-patched
to become R 4.2.2 soon?

I can confirm that the fix resolved also the original problem report
involving launching a parallel PSOCK cluster from within a 'processx'
background process
(https://stackoverflow.com/questions/73962109/why-are-the-workers-failing-to-connect-when-calling-makepsockcluster-from-an-e/73991833#73991833
and https://github.com/r-lib/callr/issues/236)


/Henrik

On Mon, Oct 10, 2022 at 5:54 AM peter dalgaard <pdalgd using gmail.com> wrote:
>
> It seems to work simply to do  "if (ifd >= 0)..." (the ifp test is fine since ifp is FILE* and initialized to NULL). Will commit (to r-devel for now).
>
> -pd
>
> > On 10 Oct 2022, at 11:07 , peter dalgaard <pdalgd using gmail.com> wrote:
> >
> > He!
> >
> > Yes, that looks like a blunder.
> >
> > mkstemp() returns -1 on failure, not 0, so the test on ifd (and I suppose also the one on ifp) is wrong. And of course, once you close file descriptor 0, mkstemp() chooses the 1st available fd, i.e. 0, for its return value.
> >
> > -pd
> >
> >> On 9 Oct 2022, at 20:25 , Henrik Bengtsson <henrik.bengtsson using gmail.com> wrote:
> >>
> >> Rscript fails to launch if the standard input (stdin) is closed, e.g.
> >>
> >> $ Rscript --vanilla -e 42 0<&-
> >> Fatal error: creating temporary file for '-e' failed
> >>
> >> This appear to only happen with `-e EXPR`, e.g. it works when doing:
> >>
> >> $ echo "42" > script.R
> >> $ Rscript --vanilla script.R 0<&-
> >> [1] 42
> >>
> >> and:
> >>
> >> $ R --vanilla 0<&-
> >> R version 4.2.1 (2022-06-23) -- "Funny-Looking Kid"
> >> Copyright (C) 2022 The R Foundation for Statistical Computing
> >> Platform: x86_64-pc-linux-gnu (64-bit)
> >> ...
> >>>
> >>
> >>
> >> TROUBLESHOOTING:
> >>
> >> $ strace Rscript --vanilla -e 42 0<&-
> >> execve("/home/hb/shared/software/CBI/R-4.2.1-gcc9/bin/Rscript",
> >> ["Rscript", "--vanilla", "-e", "42"], 0x7fff9f476418 /* 147 vars */) =
> >> 0
> >> brk(NULL)                               = 0x5625ca9e6000
> >> arch_prctl(0x3001 /* ARCH_??? */, 0x7fff23b4d260) = -1 EINVAL (Invalid argument)
> >> ...
> >> fstat(1, {st_mode=S_IFCHR|0620, st_rdev=makedev(0x88, 0), ...}) = 0
> >> write(1, "Fatal error: creating temporary "..., 53Fatal error:
> >> creating temporary file for '-e' failed
> >> ) = 53
> >> exit_group(2)                           = ?
> >> +++ exited with 2 +++
> >>
> >> which points to src/unix/system.c:
> >>
> >> ifd = mkstemp(ifile);
> >> if (ifd > 0)
> >>   ifp = fdopen(ifd, "w+");
> >> if(!ifp) R_Suicide(_("creating temporary file for '-e' failed"));
> >>
> >>
> >> One rationale for having closed standard files (including stdin) is to
> >> avoid leaking file descriptors, cf.
> >> https://wiki.sei.cmu.edu/confluence/display/c/FIO22-C.+Close+files+before+spawning+processes
> >> and https://danwalsh.livejournal.com/53603.html.  The background for
> >> reporting on this was that `system()` fails to work in processx
> >> spawned processes, which closes the standard files by default in
> >> processx (<= 3.7.0).
> >>
> >> Best,
> >>
> >> Henrik
> >>
> >> ______________________________________________
> >> R-devel using r-project.org mailing list
> >> https://stat.ethz.ch/mailman/listinfo/r-devel
> >
> > --
> > Peter Dalgaard, Professor,
> > Center for Statistics, Copenhagen Business School
> > Solbjerg Plads 3, 2000 Frederiksberg, Denmark
> > Phone: (+45)38153501
> > Office: A 4.23
> > Email: pd.mes using cbs.dk  Priv: PDalgd using gmail.com
> >
>
> --
> Peter Dalgaard, Professor,
> Center for Statistics, Copenhagen Business School
> Solbjerg Plads 3, 2000 Frederiksberg, Denmark
> Phone: (+45)38153501
> Office: A 4.23
> Email: pd.mes using cbs.dk  Priv: PDalgd using gmail.com
>