Module hierarchy.: It should respect the C++ hierarchy. At the moment, the topmost module is hpp. The other module should either be as in C++ or suffixed with _idl. Suffixing is usefull to prevent name collisions.

IDL comments prefix

They are used to trigger particular behavior.

'// ' is a standard comment (two slashes followed by one space).
'//*' replaces the automatic implementation by the code provided. All consecutive lines starting with this prefix will be used.

You also find them after the hpp module. The code in this context will be put at the beginning of the generated C++ file. This is useful to include C++ headers.
'//->' is used to rename a function, a module or an interface (the last may not be implemented yet).
'///' is a comment used to generate the documentation (by Python and Doxygen).

What to do when the automatic implementation does not work ?

The compiler should tell you what function fails.
Understand why this function fails. You can modify the file in the build folder.
When your changes work as expected, copy the code in a comment block for code (i.e. comments starts with //*) just after the function declaration. No need to include the try/catch block.

As an example, take function DifferentiableFunction.value, in idl/hpp/constraints_idl/constraints.idl. The automatic implementation for this function cannot work since LieGroupElement cannot be converted (at least, as of now). So you must provide a implementation. Have a look at the comment in the file.

Use CMake to generate the C++ implementation of your IDL.: The best is to have a look at src/CMakeLists.txt. Eventually, hpp-manipulation-corba/src/CMakeLists.txt may be informative. Most of the complexity is hidden behind the CMake macros GENERATE_IDL_PYTHON, GENERATE_IDL_CPP and GENERATE_IDL_CPP_IMPL.

If you encounter an error related to a module not found, it may be because you forgot an option -Wbextern=... in the CMake function GENERATE_IDL_PYTHON

Todo:: The fact that one must specify what are the external module, for the Python client, is very annoying. One workaround could be to generate only one big Python file instead of plenty of separated ones. To do this, it should be sufficient to pass multiple IDL files to omniidl.