> I understand that LoadLibraryExW() must not be attempted if _Py_dll_path is empty, or if Py_GetPrefix() is empty. Am I right?

More likely those should never be empty. Perhaps sys.prefix is optional, but the DLL path is the current executing module, and should always be set.

I suspect you're right, that 3.7 is also affected. But earlier versions would only _not_ fill the DLL path for static (non-shared) builds.

It looks like Py_SetPath in 3.7 started clearing it unnecessarily, so that may be the cause.