passing pointer from nim dynlib to c host application

[alexgustafson]

I am working on a nim wrapper for the CLAP audio plugin format.

I can compile an audio plugin written in nim as a dynlib and load it into a 
test host ( written in c ). The host is finding the exposed methods and 
endpoints that it needs to create a plugin instance, however I am having 
trouble passing a pointer to a nim object to the host.

The c code that is calling into the nim dynlib looks like this ( simplified )
    
    
    auto inst = factory->create();
    
    
    Run

create() should return an instance of a plugin, however it returns NULL. the 
nim code looks like this ( simplified )
    
    
    proc create(): ptr ClapPlugin =
      var plugin: ClapPlugin = ClapPlugin(
        desc: addr(sMyPlugDesc),
        startProcessing: myPlugStartProcessing,
        stopProcessing: myPlugStopProcessing,
        process: myPlugProcess,
      )
      echo "created plugin"
      return addr plugin
    
    
    Run

The echo message indicates that the message is being called correctly, however 
the variable "inst" in the c part is NULL. In c the plugin creation method 
would look like this:
    
    
    clap_plugin_t *my_plug_create(const clap_host_t *host) {
       my_plug_t *p = calloc(1, sizeof(*p));
       p->plugin.desc = &s_my_plug_desc;
       p->plugin.start_processing = my_plug_start_processing;
       p->plugin.stop_processing = my_plug_stop_processing;
       p->plugin.process = my_plug_process;
       return &p->plugin;
    }
    
    
    Run

I am guessing that the instantiated object is being deleted as it leaves the 
proc's scope. Do I need to alloc it's memory explicitly in nim? or can I use a 
ref object?

Any tips would be appreciated.