[Users] C++ interface of HDF5

[Christian Reisswig]

Hi,

> Currently, the HDF5 thorn within ExternalLibraries provides the C++
> interface of the hdf5 library by default. However, nothing within the
> toolkit makes use of it. The C++ interface is considered deprecated by
> hdf5 itself. It doesn't work together with parallel hdf5.
> 
> Thus, I suggest to not build and look for the C++ interface by default.
> 
> The benefit would be that typical system installations (which don't come
> with the c++ interface) can be used without explicitly specifying flags
> in the optionlist. Also, parallel hdf5 could be used more easily.
> 
> A disadvantage would be of course that it would not be available by
> default anymore. However, nothing within the Einstein Toolkit actually
> uses it.
> 
> On argument so far had been that the Carpet hdf5 visit reader uses it.
> However, because of hdf5 version conflicts it is usually better anyway
> to build the reader against the headers that come with a visit
> installation. Cactus isn't needed here at all.

The Carpet Visit reader uses the C version instead of C++ of hdf5 by now. I 
have ported that to C because the VisIt team did not plan to include hdf5-c++ 
in their release. So in order to get the reader into VisIt, it has to use C.

Christian
 
> Please comment on the corresponding ticket [1] if you have an opinion
> about this, e.g. if you use the C++ interface. If nobody speaks up the
> C++ interface will be dropped (by default) in about two weeks. It would
> still be possible to specify HDF5_ENABLE_CXX=yes in an optionlist to
> make sure it is present.
> 
> Frank Loeffler
> 
> [1] https://trac.einsteintoolkit.org/ticket/669