libreadline SIGINT处理程序不清除缓冲区

Question

有了下面的小程序，我期待以下内容：

>> forget_me!^C
>> next
next
>>

但它确实是：

>> forget_me!^C
>> next
forget_me!next
>>

不应该默认的SIGINT处理程序清除缓冲区，如http://sunsite.ualberta.ca/Documentation/Gnu/readline-4.1/html_node/readline_40.html#SEC40（rl_free_line_state）所述？

如何达到预期效果？

#include <cstdlib>
#include <csignal>
#include <iostream>
#include <readline/readline.h>
#include <readline/history.h>

const std::string prompt{">> "};

void new_line_handler(int i) { std::cout << "\n" << prompt; }

int main() {
  struct sigaction action = {};
  action.sa_handler = new_line_handler;
  sigaction(SIGINT, &action, nullptr);

  char *input;
  while (true) {
    input = readline(prompt.c_str());
    if (!input)
      break;
    add_history(input);
    std::cout << input << "\n";
    free(input);
  }
  return 0;
}