c++ - basic_regex 使用 char32_t 抛出 bad_cast

Question

为什么下面的代码会产生std::bad_cast异常？

#include <iostream>
#include <regex>
#include <string>

int main()
{
    std::basic_string<char32_t> reg = U"^\\w";

    try
    {
        std::basic_regex<char32_t> tagRegex(reg);
    }
    catch(std::exception &e)
    {
        std::cout << e.what() << std::endl;
    }

    return 0;
}

为方便起见，Ideone 上的示例:https://ideone.com/Saea88

使用 char 或 wchar 而不是 char32_t 运行时不会抛出(证明:https://ideone.com/OBlXed)。

Answer 1

您可以在这里找到:http://en.cppreference.com/w/cpp/regex/regex_traits :

To use std::basic_regex with other character types (for example, char32_t), a user-provided trait class must be used.

所以你必须实现std::regex_traits<char32_t>

要了解为什么没有定义，请看这里:Why is there no definition for std::regex_traits<char32_t> (and thus no std::basic_regex<char32_t>) provided?