The new doctesting framework doesn't like being run with nohup

[kiwifb]

When run inside nohup test are failing to run with the new doctesting framework in 5.9.beta0. An example

fbissey@QCD-nzi3 /home/work/fbissey/sandbox/sage-5.9.beta0 $ ./sage -t --long "devel/sage-main/sage/misc/inline_fortran.py"
Running doctests with ID 2013-03-19-22-26-09-85e3b5eb.
Doctesting 1 file.
sage -t --long devel/sage-main/sage/misc/inline_fortran.py
    [10 tests, 1.1 s]
----------------------------------------------------------------------
All tests passed!
----------------------------------------------------------------------
Total time for all tests: 1.1 seconds
    cpu time: 0.1 seconds
    cumulative wall time: 1.1 seconds

But when the same thing is run with nohup

nohup ./sage -t --long "devel/sage-main/sage/misc/inline_fortran.py" &

The output is

Running doctests with ID 2013-03-19-22-26-21-d52d31ab.
Doctesting 1 file.
sage -t --long devel/sage-main/sage/misc/inline_fortran.py
Process DocTestWorker-1:
Traceback (most recent call last):
  File "/home/work/fbissey/sandbox/sage-5.9.beta0/local/lib/python/multiprocessing/process.py", l
ine 258, in _bootstrap
    self.run()
  File "/home/work/fbissey/sandbox/sage-5.9.beta0/local/lib/python2.7/site-packages/sage/doctest/
forker.py", line 1655, in run
    sys.stdin = os.fdopen(0, "r")
OSError: [Errno 22] Invalid argument
    Bad exit: 1
**********************************************************************
Tests run before process failed:

**********************************************************************
----------------------------------------------------------------------
sage -t --long devel/sage-main/sage/misc/inline_fortran.py  # Bad exit: 1
----------------------------------------------------------------------
Total time for all tests: 0.0 seconds
    cpu time: 0.0 seconds
    cumulative wall time: 0.0 seconds

This is with the following version of nohup

nohup --version
nohup (GNU coreutils) 8.20
Packaged by Gentoo (8.20 (p1.0))
Copyright (C) 2012 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>.
This is free software: you are free to change and redistribute 

Depends on #12415

CC: @jdemeyer

Component: doctest framework

Author: Jeroen Demeyer

Reviewer: François Bissey

Merged: sage-5.9.beta1

Issue created by migration from https://trac.sagemath.org/ticket/14307

[jdemeyer]

comment:1

Please add the output of

nohup --version

[jdemeyer]

comment:2

nohup is crazy. It opens the standard input for writing and claims it's a feature. From nohup sources:

  /* If standard input is a tty, replace it with /dev/null if possible.
     Note that it is deliberately opened for *writing*,
     to ensure any read evokes an error.  */
  if (ignoring_input)
    {
      if (fd_reopen (STDIN_FILENO, "/dev/null", O_WRONLY, 0) < 0)
        {
          error (0, errno, _("failed to render standard input unusable"));
          exit (exit_internal_failure);
        }
      if (!redirecting_stdout && !redirecting_stderr)
        error (0, 0, _("ignoring input"));
    }

[kiwifb]

Description changed:

--- 
+++ 
@@ -45,4 +45,13 @@
     cpu time: 0.0 seconds
     cumulative wall time: 0.0 seconds
 ```
+This is with the following version of nohup
 
+```
+nohup --version
+nohup (GNU coreutils) 8.20
+Packaged by Gentoo (8.20 (p1.0))
+Copyright (C) 2012 Free Software Foundation, Inc.
+License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>.
+This is free software: you are free to change and redistribute 
+```

[kiwifb]

comment:3

Updated the summary with nohup version as asked. Sounds crazy all right.

[kiwifb]

comment:4

From the info page this is a GNU extension

   If standard input is a terminal, it is redirected from `/dev/null'
so that terminal sessions do not mistakenly consider the terminal to be
used by the command.  This is a GNU extension; programs intended to be
portable to non-GNU hosts should use `nohup COMMAND [ARG]... </dev/null'
instead.

I guess I will try the last bit.

[kiwifb]

comment:5

Yes that's a cure

nohup ./sage -t --long "devel/sage-main/sage/misc/inline_fortran.py" </dev/null &

Does work as intended. I guess we can close this as invalid. I have just learnt about a GNU extension that has interesting side effects.

[jdemeyer]

Attachment: 14307_bad_stdin.patch.gz

[jdemeyer]

comment:6

It's also good anyway to fix the doctester to handle this case, needs review.

[jdemeyer]

Dependencies: #12415

[jdemeyer]

Author: Jeroen Demeyer