I've followed the links you've given (thanks!) and done some more tests. To clarify, I have issues similar to the cpython folks (https://openradar.appspot.com/radar?id=5536824084660224), except that I am my own customer; I am the only one linking loadable module .so dynamic libraries to my interpreter. No one else will need to build a module for my interpreter to load - which may simplify things a bit (I don't think I'll need a framework). (continued... after stupid posting length rules)

I've tried a lot of flags, -no_fixup_chains, -no_compact_unwind, -undefined suppress , -undefined dynamic_lookup. -bundle with -bundle_loader , and also placing all 300+ symbols on the link command line with -Wl,-U,. -bundle -bundle_loader -Wl,-no_compact_unwind and -undefined dynamic_lookup -Wl,-no_compact_unwind -Wl,-no_fixup_chains can produce a loadable module .so without errors (and all of the above with and without -flat_namespace), ....

... but my interpreter cannot load either at runtime. Most frustrating is that I don't see any errors. If there are missing symbols, I should be able to find something, right? Is there a system log, or something like LD_DEUBG, that can provide a bit more information? When linking the interpreter, I assume I need -Wl,-export_dynamic so the system dyld(?) loader can find and resolve the loaded module .so against the interpreter ... but clearly I'm still missing something.