How do you fully initialize an embedded ruby VM in a C++ application?

Question

I am embedding ruby version 2.1.2 into a wxWidgets application, compiling on - and targeting - Windows. Linking to msvcrt-ruby210.dll and calling

ruby_sysinit(&argc, &argv);
RUBY_INIT_STACK;
ruby_init();
ruby_init_loadpath();

is enough to get me running with the basic VM and built-in classes. However, I am also packaging the standard library with my application, as I intend use facilities like FileUtils and Resolv from my application. I can require and use some of the libraries just fine, yet when I require 'resolv' I get an error reporting unitialized constant Encoding::UTF_16LE. After some googling and digging around in ruby.c, I've found I can fix this with the following initialization code...

ruby_sysinit(&argc, &argv);
RUBY_INIT_STACK;
ruby_init();
ruby_init_loadpath();
rb_enc_find_index("encdb");

Which clears the previous error, but leaves me with code converter not found (UTF-8 to UTF-16LE). This is fixed by adding an additional line rb_eval_string("require 'enc/trans/transdb'");, but, it is not my desire to replicate, piece by piece, the initialization code performed by ruby's ruby_options function, so I tried to use it directly, as in ruby's own main function...

int my_argc = 2;
char* arg1 = "myapp.exe";
char* arg2 = "scripts/bootstrap.rb";
char** my_argv = new char*[2]{arg1, arg2};

ruby_sysinit(&my_argc, &my_argv);
RUBY_INIT_STACK;
ruby_init();
ruby_run_node(ruby_options(my_argc, my_argv));

This, however, is only effective if I run my application with myapp.exe scripts/bootstrap.rb. It seems that ruby is ignoring my parameters to ruby_options and using the system supplied values of argc & argv (Apparently this has been the case for some time on Windows). This is bothersome, as I would like my application to run with a simple double-click of the executable, and not require users to supply command line arguments indicating the location of the "bootstrap" script.

So, is there a convenient API or some incantation I can use to initialize ruby in this case without requiring the command line parameters?

Note that if at all possible, I would like to avoid having to package my application as a ruby extension.

Answer 1

I noticed this code in pepper_main.c, and suspected this was doing about what I wanted.

static VALUE
init_libraries_internal(VALUE unused)
{
  extern void Init_enc();
  extern void Init_ext();

  init_loadpath();
  Init_enc();
  Init_ext();
  return Qnil;
}

As far as I can figure, I don't need Init_ext() since I'm using the ruby dll, and I'm not statically compiling my extensions. So, I tried just using Init_enc. While this symbol is present in the msvcrt-ruby210.dll, it's not present in the import library (msvcrt-ruby210.dll.a) so I wasn't able to link it with my application. Searching through the symbols in the .so files under the lib\ruby\2.1.0\i386-mingw32\enc directory, I was able to find Init_encdb in encdb.so, and Init_transdb in trans/transdb.so. So, I've required these libs and my bootstrap script as shown below:

ruby_sysinit(&argc, &argv);
RUBY_INIT_STACK;
ruby_init();
ruby_init_loadpath();
rb_require("enc/encdb");
rb_require("enc/trans/transdb");
rb_require("./scripts/bootstrap");

This enables me to use the FileUtils and Resolv libraries without error. While I can't be sure I won't run into more issues like this (I've yet to try requiring an actual gem...) this is a solution I'm more comfortable with. If I can resolve any forthcoming issues with a simple require, as opposed to digging around to find obscure commands like rb_enc_find_index("encdb"); to sprinkle into my initialization code, then that seems reasonable.

I am still interested in any simpler alternatives, and will hold off on accepting this as the answer - for a while, at least - until I receive some confirmation that I'm going about this correctly.