C functions returning struct pointers: how to deal with them?

[jowilkes]

Sorry if I am asking something "obvious"; but neither the Type Mapping page, nor ninety minutes of web searches did yield anything in this regard, so maybe it is best to ask at the source.

I try to JNR-FFI-map a certain library (X11), and the very first function I need to call returns an pointer to a struct.
I checked the C header files, yes, it returns an pointer to this struct.
It is not a case where you supply a buffer or pointer-to-pointer; these I know.

Now I did try to define the struct, and declare the interface entry thus: TheStruct functionName(String parameter).
Kaboom: segfault.

What is the correct approach to map such a function to JNR FFI?