Subforge

Ruby lacks a way to proper init the load path for gems without using stuff like ruby_options(), which will make things even worse. Generally this is, because Ruby wasn't developed to be embedded in the first place, that also explains the lack of docs about this topic.

Reading through the code these lines here are exactly what we are looking for:

Numbers: on /off 1 /* ruby.c:1055: */
 2 void Init_prelude(void);
 3 
 4 static void                                            
 5 ruby_init_gems(int enable)                                
 6 {
 7   if (enable) rb_define_module("Gem");                                   
 8   Init_prelude();                                             
 9 }

Looks good, but ruby_init_gems() is static and thus not accessable by third party like us. The workaround is to mimic the function in our code, this includes the forward declaration of Init_prelude() or our compiler will complain about it.

In subtle I use the following to init the vm:

Numbers: on /off 1 void Init_prelude(void);
 2 
 3 RUBY_INIT_STACK;
 4 ruby_init();
 5 ruby_init_loadpath();
 6 ruby_script("subtle");
 7 
 8 /* FIXME: Fake ruby_init_gems(Qtrue) */
 9 rb_define_module("Gem");
10 Init_prelude();

If you insist to know what Init_prelude() really does have a look at the miniprelude.c file of the Ruby tarball.