The struct containing func is being declared here.
For the CoreDX C typesupport it is initialized here.
The function basically provide the typesupport for a specific message which enables “generically” written code to use / interact with messages which were not available at compile time but which have been defined later.
I would suggest to build in Debug so that the assert’s are being checked. Additionally printing the value of handle as well as its members and identifier might provide valuable information (within message_type_support.c).
I was expecting a list of command line invocations which I can easily run by copy-and-pasting them to a console. I managed to follow your text instructions (even though bullet 7 and 8 are in the wrong order). In the future it would be great to provide ready-to-run commands (e.g. instead of letting people edit files it is more convenient to share the already edited version through Gist) since it reduces the effort to help you and makes the whole process less ambiguous.
Anyway my build finished and when I run the talker and listener I see the following error message twice:
dds_thread_set_stacksize(): pthread_attr_setstacksize() error(22):Invalid argument
Beside that the talker is printing Publishing: "Hello World: N" and the listener I heard: [Hello World: N] so that seems to work just fine for me. Note: I built Debug since I expected the need to debug asserts / segfaults / etc.