If the D code is aware that it needs to initialize the runtime then yes, either that you or you initialize it yourself before using it. rt_init will fire up th

If the D code is aware that it needs to initialize the runtime then yes, either that you or you initialize it yourself before using it. rt_init will fire up the D runtime. As for constructors the runtime should handle those when the module is initialised, so not necessarily on program start up or the DSO being loaded. If, however, you want to register a C runtime constructor you can do do so with pragma(crt_constructor). I actually recently-ish fixed a bug to make the aforementioned type of constructor work on MacOS because Apple decided to deprecate them with no reason.