[netCDF #ZES-283112]: [netcdfgroup] netcdf c++ interface does not propagate errors in NcFile constructor

Hi Heiko,

Sorry to have taken so long to respond to your email ...
> when opening a netcdf-file with the (old) cpp interface of netcdf, e.g.
> new NcFile(filename, NcFile::ReadOnly)
> it is not possible to catch any error, e.g. "No such file or directory".
> 
> The problem is that NcFile::NcFile internally sets
> 
> NcError err(NcError::silent_nonfatal); // constructor must not fail
> 
> but when the NcFile constructor finishes, the destructor of NcError is
> called, which will reset the NcError.

Right, that's why the documentation recommends using the is_valid() member
function after an attempted open to determine whether it succeeded or failed:

  The constructor will not fail, but in the case of a bad path name,
  improper permissions, or if the file already exists and you have
  specified FileMode as New, no netCDF file will be created or
  opened. If the constructor fails to create or open a netCDF file, a
  subsequent call to the is_valid() member function will return False.

This would be handled better with Exceptions (as the new netCDF-4 C++ API does)
but Exceptions weren't in the C++ standard back when this was written.  The new
C++ netCDF-4 API is documented here:

  http://www.unidata.ucar.edu/netcdf/docs/cxx4/

It currently can read any kind of netCDF file, but can only create netCDF-4
files.  A little work is needed in the constructors to support creating classic
format, 64-bit offset, and netCDF-4 classic model files ...

--Russ


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



Ticket Details
===================
Ticket ID: ZES-283112
Department: Support netCDF
Priority: High
Status: Closed