std::filesystem::last_write_time是否要求最低Windows 10版本？

最简复现代码 #

#include <fstream>
#include <iostream>
#include <filesystem>

int main()
{
    auto last_write_time = std::filesystem::temp_directory_path() / "last_write_time.txt";
    std::ofstream(last_write_time.c_str()) << "Hello, World!";

    try
    {
        auto ftime = std::filesystem::last_write_time(last_write_time);
        std::cout << ftime << std::endl;
    }
    catch (const std::exception& e)
    {
        std::cerr << e.what() << std::endl;
    }

    std::filesystem::remove(last_write_time);
}

测试结果 #

• Windows 10 Enterprise 2016 LTSB Version 1607：抛出异常，信息为"unknown error"
• 同版本另一台机器：抛出异常，信息为"The specified module could not be found."
• Windows 7 Embedded Standard 6.1.7601 Service Pack 1 Build 7601：抛出异常，信息为"The specified module could not be found."
• Windows 10 Pro Version 22H2：可正常运行
• Windows 11 Enterprise Version 23H2：可正常运行

原因说明 #

根据微软STL的VS2019 16.10版本更新内容，std::filesystem::last_write_time与std::chrono::current_zone类似，对Windows系统版本有最低要求——仅支持Windows 10及以上版本。旧版Windows系统（如Windows 7、Windows 10 1607 LTSB）缺少该API底层依赖的系统模块或功能，因此调用时会触发找不到模块或未知错误的异常。

兼容方案 #

如果需要兼容旧版Windows系统，可以改用Win32原生API实现文件修改时间的获取，例如使用GetFileTime函数，示例如下：

#include <fstream>
#include <iostream>
#include <windows.h>
#include <chrono>
#include <filesystem>

int main()
{
    const auto file_path = std::filesystem::temp_directory_path() / "last_write_time.txt";
    std::ofstream(file_path.c_str()) << "Hello, World!";

    HANDLE hFile = CreateFileW(file_path.c_str(), GENERIC_READ, FILE_SHARE_READ, nullptr, OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL, nullptr);
    if (hFile != INVALID_HANDLE_VALUE)
    {
        FILETIME ftWrite;
        if (GetFileTime(hFile, nullptr, nullptr, &ftWrite))
        {
            // 转换为std::chrono时间点
            ULARGE_INTEGER ul;
            ul.LowPart = ftWrite.dwLowDateTime;
            ul.HighPart = ftWrite.dwHighDateTime;
            auto duration = std::chrono::microseconds(ul.QuadPart * 10);
            auto ftime = std::chrono::file_time_type(duration);
            std::cout << "Last write time: " << ftime.time_since_epoch().count() << std::endl;
        }
        else
        {
            std::cerr << "GetFileTime failed: " << GetLastError() << std::endl;
        }
        CloseHandle(hFile);
    }
    else
    {
        std::cerr << "CreateFile failed: " << GetLastError() << std::endl;
    }

    std::filesystem::remove(file_path);
}

内容的提问来源于stack exchange，提问作者Kevin Haybach