[netCDF #IDL-671230]: NetCDF C++ Library

Hi Phil,

> Hope you don't mind. I have some questions about the NetCDF-C++ library.
> 
> Why do the instructions mention that the interface requires the
> additional flag "--enable-netcdf-4" to be used, yet the example uses
> the flag "--enable-cxx-4". I used neither, and everything seems to work
> correctly. I can compile and run at least one of the examples. 

I think Google has probably pointed you to an old install document, e.g.

  
https://www.unidata.ucar.edu/software/netcdf/docs/netcdf-install/Configure.html

that was intended for building netCDF-4 when the C++ and Fortran
libraries were bundled with the netCDF-C library. That's no longer the
case, they are now separate distributions and the netcdf-cxx4 library
depends on the netcdf-c library that must be installed first.

The closest thing to current instructions for installing netcdf-cxx4 would
be to use the up-to-date instructions for installing netCDF-Fortran, but
substituting C++ for Fortran and ignoring parts that don't apply to C++

  http://www.unidata.ucar.edu/software/netcdf/docs/building_netcdf_fortran.html

> ... However,
> this is only possible if I link to the static (*.a) libraries. I am
> finding that any attempt to use the dynamic (*.so) library produces the
> following error:
> 
> error while loading shared libraries: libnetcdf_c++4.so.1:
> cannot open shared object file: No such file or directory

I think that's probably because you need to either set LD_LIBRARY_PATH to
include the directory where you installed libnetcdf_c++4 or follow these
instructions that "make install" should have printed oput at then end of
a successful install:

  If you ever happen to want to link against installed libraries in a
  given directory, LIBDIR, you must either use libtool, and specify
  the full pathname of the library, or use the `-LLIBDIR' flag during
  linking and do at least one of the following:

     - add LIBDIR to the `LD_LIBRARY_PATH' environment variable
       during execution
     - add LIBDIR to the `LD_RUN_PATH' environment variable
       during linking
     - use the `-Wl,-rpath -Wl,LIBDIR' linker flag
     - have your system administrator add LIBDIR to `/etc/ld.so.conf'

  See any operating system documentation about shared libraries for
  more information, such as the ld(1) and ld.so(8) manual pages.

> This is despite the fact that both the static and dynamic libraries are
> available in same directory.

Right, it's a security thing that using shared libraries is not as 
straightforward as static libraries, but there are other advantages.

> In addition to the above, I found (after a few hours of confusion)
> that the order of linking is critical. Compilation has to link to
> libhdf5_hl.a *before* libhdf5.a. Otherwise, compilation fails.
> 
> Is there any more substantial documentation available anywhere?

Sorry we don't have any C++ installation documentation available yet.
It's sort of on the back burner, and currently lacks assigned resources.

--Russ

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Russ Rew                                         UCAR Unidata Program
address@hidden                      http://www.unidata.ucar.edu



Ticket Details
===================
Ticket ID: IDL-671230
Department: Support netCDF
Priority: Normal
Status: Closed