use pre-allocated RuntimeError for out-of-memory

include/mruby.h

@@ -167,6 +167,7 @@ typedef struct mrb_state {
 
   struct RClass *eException_class;
   struct RClass *eStandardError_class;
+  struct RObject *nomem_err;              /* pre-allocated NoMemoryError */
 
   void *ud; /* auxiliary data */
 } mrb_state;

src/error.c

@@ -227,7 +227,9 @@ mrb_noreturn void
 mrb_exc_raise(mrb_state *mrb, mrb_value exc)
 {
   mrb->exc = mrb_obj_ptr(exc);
-  exc_debug_info(mrb, mrb->exc);
+  if (!mrb->out_of_memory) {
+    exc_debug_info(mrb, mrb->exc);
+  }
   if (!mrb->jmp) {
     mrb_p(mrb, exc);
     abort();
@@ -459,7 +461,7 @@ mrb_no_method_error(mrb_state *mrb, mrb_sym id, mrb_int argc, const mrb_value *a
 void
 mrb_init_exception(mrb_state *mrb)
 {
-  struct RClass *exception, *script_error;
+  struct RClass *exception, *runtime_error, *script_error;
 
   mrb->eException_class = exception = mrb_define_class(mrb, "Exception", mrb->object_class);                   /* 15.2.22 */
   mrb_define_class_method(mrb, exception, "exception", mrb_instance_new,  MRB_ARGS_ANY());
@@ -472,7 +474,8 @@ mrb_init_exception(mrb_state *mrb)
   mrb_define_method(mrb, exception, "backtrace",       mrb_exc_backtrace, MRB_ARGS_NONE());
 
   mrb->eStandardError_class = mrb_define_class(mrb, "StandardError", mrb->eException_class);           /* 15.2.23 */
-  mrb_define_class(mrb, "RuntimeError", mrb->eStandardError_class);                                    /* 15.2.28 */
+  runtime_error = mrb_define_class(mrb, "RuntimeError", mrb->eStandardError_class);                                    /* 15.2.28 */
+  mrb->nomem_err = mrb_obj_ptr(mrb_exc_new_str(mrb, runtime_error, mrb_str_new_lit(mrb, "Out of memory")));
   script_error = mrb_define_class(mrb, "ScriptError", mrb->eException_class);                                     /* 15.2.37 */
   mrb_define_class(mrb, "SyntaxError", script_error);                                                             /* 15.2.38 */
 }

src/gc.c

@@ -189,7 +189,7 @@ mrb_realloc(mrb_state *mrb, void *p, size_t len)
     }
     else {
       mrb->out_of_memory = TRUE;
-      mrb_raise(mrb, E_RUNTIME_ERROR, "Out of memory");
+      mrb_exc_raise(mrb, mrb_obj_value(mrb->nomem_err));
     }
   }
   else {