[Hdf-forum] HDF lib incompatible with HDF file spec?

Latham, Robert J. robl at mcs.anl.gov
Tue Sep 5 14:22:45 CDT 2017

On Tue, 2017-09-05 at 17:21 +0000, Miller, Mark C. wrote:
> Hmm. If I understand you, you have written code that you believe
> produces an HDF5 file according to the 3.0 file version
> specification, https://support.hdfgroup.org/HDF5/doc/H5.format.html
> but nevertheless does NOT use the HDF5 library to do it. Furthermore,
> where 'extended padding' is concerned, your implementation does
> business differently than the HDF5 implementation.
> You can prove HDF5 tools will *read* the file ok. But, in a read-
> modify-write scenario, the file is getting corrupted by HDF5 library
> due to the difference in how the two implementations handle the
> extended padding -- a feature that you explain is '...not defined at
> all -- not even recommended'.
> Is that about right?
> If so, it does indeed sound like a potential issue in the file format
> specification for HDF5.
> Your scenario sounds like a super useful test case...does a wholly
> independent implementation produce a file the HDF5 library can
> "handle"?

Over in Parallel-NetCDF land a few years back, we took, um, a "rather
aggressive interpretation" of the NetCDF spec with respect to alignment
and then opend a bug with Unidata when their tools did not follow the
rules as written.

As Mark observes, it was a productive exercise in keeping both
implementations honest.


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