In addition to my last post, I have one more note to share.
Whenever I changed any port data type, I recreated the ‘Verilog .DLL C++ main template’.
Verilog sources are converted to ‘C/C++’ sources by ‘Verilator’, so it seems that we must update not only the Verilog source but also the ‘Verilog .DLL C++ main’.