For debugging with eclipse create a C++ project and use Eclipse CDT.
When debugging with gdb you will see the FeatureC++ source code.
It is not needed to look at the intermediate C++ code.
When using cygwin, there has to be a mapping of cygwin paths to windows paths:
1. Start debugging and select cygwin gdb as debugger.
2. When the "source not found" window appears, create a path mapping for cygwin gdb.
a) Click on the "Edit source lookup" button
b) Click on the "Add..." button
3. Select "Path Mapping" and click OK.
4. Create a mapping:
a) Enter a name and click the "Add" to create a mapping.
b) enter the cygwin path to map from and the local corresponding path