pre-allocate arena overflow error

include/mruby.h

@@ -221,6 +221,9 @@ typedef struct mrb_state {
   struct RClass *eException_class;
   struct RClass *eStandardError_class;
   struct RObject *nomem_err;              /* pre-allocated NoMemoryError */
+#ifdef MRB_GC_FIXED_ARENA
+  struct RObject *arena_err;              /* pre-allocated arena overfow error */
+#endif
 
   void *ud; /* auxiliary data */
 

src/error.c

@@ -465,7 +465,7 @@ exception_call:
   }
   if (argc > 0) {
     if (!mrb_obj_is_kind_of(mrb, mesg, mrb->eException_class))
-      mrb_raise(mrb, E_TYPE_ERROR, "exception object expected");
+      mrb_raise(mrb, mrb->eException_class, "exception object expected");
     if (argc > 2)
       set_backtrace(mrb, mesg, argv[2]);
   }
@@ -532,6 +532,9 @@ mrb_init_exception(mrb_state *mrb)
   mrb->eStandardError_class = mrb_define_class(mrb, "StandardError", mrb->eException_class); /* 15.2.23 */
   runtime_error = mrb_define_class(mrb, "RuntimeError", mrb->eStandardError_class);          /* 15.2.28 */
   mrb->nomem_err = mrb_obj_ptr(mrb_exc_new_str_lit(mrb, runtime_error, "Out of memory"));
+#ifdef MRB_GC_FIXED_ARENA
+  mrb->arena_err = mrb_obj_ptr(mrb_exc_new_str_lit(mrb, runtime_error, "arena overflow error"));
+#endif
   script_error = mrb_define_class(mrb, "ScriptError", mrb->eException_class);                /* 15.2.37 */
   mrb_define_class(mrb, "SyntaxError", script_error);                                        /* 15.2.38 */
   mrb_define_class(mrb, "SystemStackError", exception);

src/gc.c

@@ -403,7 +403,7 @@ gc_protect(mrb_state *mrb, mrb_gc *gc, struct RBasic *p)
   if (gc->arena_idx >= MRB_GC_ARENA_SIZE) {
     /* arena overflow error */
     gc->arena_idx = MRB_GC_ARENA_SIZE - 4; /* force room in arena */
-    mrb_raise(mrb, E_RUNTIME_ERROR, "arena overflow error");
+    mrb_exc_raise(mrb, mrb_obj_value(mrb->arena_err));
   }
 #else
   if (gc->arena_idx >= gc->arena_capa) {
@@ -816,6 +816,9 @@ root_scan_phase(mrb_state *mrb, mrb_gc *gc)
   mrb_gc_mark(mrb, (struct RBasic*)mrb->exc);
   /* mark pre-allocated exception */
   mrb_gc_mark(mrb, (struct RBasic*)mrb->nomem_err);
+#ifdef MRB_GC_FIXED_ARENA
+  mrb_gc_mark(mrb, (struct RBasic*)mrb->arena_err);
+#endif
 
   mark_context(mrb, mrb->root_c);
   if (mrb->root_c->fib) {