[Scons-users] Determining source of scons crash

[Luke Robison]

I'm trying to track down a crash I have triggered in scons (both 3.0.1 and
3.1.2).  This crash only happens when I ask scons to build my entire output
directory (it will happily compile if my command-line target is
build-variant/my_prog.exe, but giving it the target build-variant causes
the crash).

AttributeError: 'NoneType' object has no attribute 'get_build_env':
  File "/usr/lib/scons/SCons/Script/Main.py", line 1376:
    _exec_main(parser, values)
  File "/usr/lib/scons/SCons/Script/Main.py", line 1339:
    _main(parser)
  File "/usr/lib/scons/SCons/Script/Main.py", line 1103:
    nodes = _build_targets(fs, options, targets, target_top)
  File "/usr/lib/scons/SCons/Script/Main.py", line 1313:
    jobs.run(postfunc = jobs_postfunc)
  File "/usr/lib/scons/SCons/Job.py", line 111:
    self.job.start()
  File "/usr/lib/scons/SCons/Job.py", line 229:
    task.executed()
  File "/usr/lib/scons/SCons/Script/Main.py", line 237:
    SCons.Taskmaster.OutOfDateTask.executed(self)
  File "/usr/lib/scons/SCons/Taskmaster.py", line 312:
    t.push_to_cache()
  File "/usr/lib/scons/SCons/Node/FS.py", line 2910:
    self.get_build_env().get_CacheDir().push(self)
  File "/usr/lib/scons/SCons/Node/__init__.py", line 624:
    result = self.get_executor().get_build_env()

I have two questions:
1) How can I go about debugging this?  I found --debug=pdb to be usless
here, as I end up in Main.py calling _build_targets rather than where the
error occurs.  Similarly, I can't do --tree, since python crashes before it
gets to that point.  Modifying the scons source with print statements has
been my way forward for now.
2) Is it considered a bug to have scons crash like this (even if I may have
fed it something bad?)

After adding some prints to the scons code, It seems one of my compiled
header outputs (code is Fortran, so the compiled header is foo.mod) is the
"self" here, and self.get_executor() returns "None", and then python fails
on trying to call None.get_build_env().  This crash happens immediately
after building the relevant SharedObject file (foo.os) from the source
(foo.f90).  It doesn't happen for all files, but it happens predictably on
some, and those tend to have no dependencies themselves. Re-running the
build enough times will eventually let it complete.

Any suggestions greatly appreciated.

Luke
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