Save the register value in a local variable for ease of debugging.
MODIFY
src/vm.c
src/vm.c
@@ -1185,7 +1185,9 @@ RETRY_TRY_BLOCK:
CASE(OP_RAISE) {
/* A raise(R(A)) */
- mrb_exc_set(mrb, regs[GETARG_A(i)]);
+ int a = GETARG_A(i);
+
+ mrb_exc_set(mrb, regs[a]);
goto L_RAISE;
}

Save the register value in a local variable for ease of debugging.