How to raise errors/exceptions by default in mruby?

Question

I'm getting started with mruby and found out the hard way that an error was occurring in my code, but there was no error reporting. Maybe I am doing something wrong. How can I get errors to appear when they occur?

Excerpt from C code:

mrb = mrb_open();
FILE *f = fopen("example.rb", "r");
mrb_load_file(mrb, f);
fclose(f);
// more C code...

Ruby code which fails without reporting:

# example.rb
def my_method
  call_undefined_method
end
my_method()

Ruby code which rescues from the error to display that there was an error:

# example.rb
def my_method
  call_undefined_method
rescue => e
  puts "Error: #{e.message}"
end
my_method()

Answer 1

You can get exception via mrb->exc

#include <mruby.h>
#include <mruby/variable.h>
#include <mruby/string.h>
#include <stdio.h>

int
main(int argc, char* argv[]) {
  mrb_state* mrb = mrb_open();
  FILE *f = fopen("example.rb", "r");
  mrb_value obj = mrb_load_file(mrb, f);
  fclose(f);

  if (mrb->exc) {
    // Error
    obj = mrb_funcall(mrb, mrb_obj_value(mrb->exc), "inspect", 0);
    fwrite(RSTRING_PTR(obj), RSTRING_LEN(obj), 1, stdout);
    putc('\n', stdout);
  } else {
    obj = mrb_funcall(mrb, obj, "inspect", 0);
    fwrite(RSTRING_PTR(obj), RSTRING_LEN(obj), 1, stdout);
    putc('\n', stdout);
  }

  mrb_close(mrb);
  return 0;
}