Fix and make mruby work better

src/mruby/types.ml

@@ -0,0 +1,24 @@
+open Ctypes
+open Foreign
+
+module Mrb_state = struct
+  type t
+  type mrb_ptr = t structure ptr
+
+  let typ : t structure typ = structure "mrb_state"
+  let jmp = field typ "jmp" (ptr void)
+  let c = field typ "c" (ptr void)
+  let root_c = field typ "root_c" (ptr void)
+  let globals = field typ "globals" (ptr void)
+  let exc = field typ "exc" (ptr void)
+
+  (* as it builds by default on x86_64 linux *)
+  let padding = field typ "padding" (array 24472 char)
+  let () = seal typ
+
+  let has_error mrb_ptr =
+    let exc_val = getf !@mrb_ptr exc in
+    not (is_null exc_val)
+
+  let clear_error mrb_ptr = setf !@mrb_ptr exc null
+end