RuntimeError when writing to /dev/null

This error occur in my unit tests, where I write data to /dev/null to throw it away. It only happens when writing empty datasets. Testcase:

import h5py

with h5py.File("/dev/null", "w") as f:
    f.create_dataset("foo", data=[])
    f.create_dataset("bar", data=[])

Output:

Traceback (most recent call last):
  File "h5py-dev-null.py", line 5, in <module>
    f.create_dataset("bar", data=[])
  File "h5py/_objects.pyx", line 54, in h5py._objects.with_phil.wrapper
  File "h5py/_objects.pyx", line 55, in h5py._objects.with_phil.wrapper
  File "/home/chn/env/lib/python3.8/site-packages/h5py/_hl/files.py", line 475, in __exit__
    self.close()
  File "/home/chn/env/lib/python3.8/site-packages/h5py/_hl/files.py", line 457, in close
    h5i.dec_ref(id_)
  File "h5py/_objects.pyx", line 54, in h5py._objects.with_phil.wrapper
  File "h5py/_objects.pyx", line 55, in h5py._objects.with_phil.wrapper
  File "h5py/h5i.pyx", line 153, in h5py.h5i.dec_ref
RuntimeError: Can't decrement id ref count (unable to extend file properly, errno = 22, error message = 'Invalid argument')
Segmentation fault

The expected result is either to work correctly or fail with OSError or equivalent. Versions:

Ubuntu 20.04.1 LTS
h5py    3.1.0
HDF5    1.12.0
Python  3.8.5 (default, Jul 28 2020, 12:59:40) 
[GCC 9.3.0]
sys.platform    linux
sys.maxsize     9223372036854775807
numpy   1.18.3
cython (built with) 0.29.21
numpy (built against) 1.17.5
HDF5 (built against) 1.12.0

[kalvdans]

Finally one year later, I managed to report it upstream: https://github.com/HDFGroup/hdf5/issues/1498

[kalvdans]

That said, this should be reported upstream (either they need to fail sooner on opening the file or more gracefully on close!). As you found this can you please take care of that @kalvdans ?

Sure! Thanks a ton for pinpointing the crash - should not be hard to make a C-only reproducer now. I will post a link here when it is done.