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

[peter dalgaard]

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