C++中为什么不要定义C风格的可变参数函数

#include <cstdarg>// "severity" followed by a zero-terminated list of char*s; write the C-style strings to cerrvoid error(int severity ...){    va_list ap;             // a magic type for holding arguments    va_start(ap, severity); // arg startup: "severity" is the first argument of error()    for (;;) {        // treat the next var as a char*; no checking: a cast in disguise        char* p = va_arg(ap, char*);        if (!p) break;        cerr << p << ' ';    }    va_end(ap);             // arg cleanup (don't forget this)    cerr << '\n';    if (severity) exit(severity);}void use(){    error(7, "this", "is", "an", "error", nullptr);    error(7); // crash    error(7, "this", "is", "an", "error");  // crash    const char* is = "is";    string an = "an";    error(7, "this", "is", an, "error"); // crash}

#include <iostream>void error(int severity){    std::cerr << '\n';    std::exit(severity);}template <typename T, typename... Ts>constexpr void error(int severity, T head, Ts... tail){    std::cerr << head;    error(severity, tail...);}void use(){    error(7); // No crash!    error(5, "this", "is", "not", "an", "error"); // No crash!    std::string an = "an";    error(7, "this", "is", "not", an, "error"); // No crash!    error(5, "oh", "no", nullptr); // Compile error! No need for nullptr.}