c++ Win32如何将此函数放在单独的cpp文件上

当这是在main.cpp工作，但如果我在log.cpp得到LNK2019错误，当我调用log函数与任何数量的参数

string getDate()
{
    SYSTEMTIME localTime;
    TCHAR strTime[128];
    GetLocalTime(&localTime);
    wsprintf(strTime, "%04d_%02d_%02d_", localTime.wYear, localTime.wMonth, localTime.wDay);
    stringstream strm;
    strm << strTime;
    string date = strm.str();
    return &date[0];
}
string getHour()
{
    SYSTEMTIME localTime;
    TCHAR strTime[128];
    GetLocalTime(&localTime);
    wsprintf(strTime, "%02d:%02d:%02d >> ", localTime.wHour, localTime.wMinute, localTime.wSecond);
    stringstream strm;
    strm << strTime;
    string hour = strm.str();
    return &hour[0];
}
void addToStream(stringstream& /*a_stream*/)
{
}
template<typename T, typename... Args>
void addToStream(stringstream& a_stream, const T& a_value, Args... a_args)
{
    a_stream << a_value;
    addToStream(a_stream, a_args...);
}
template<typename... Args>
void log(Args... a_args)
{
    stringstream strm;
    addToStream(strm, a_args...);
    string s = strm.str();
    HKEY key;
    char appPath[1024];
    DWORD appPathLength = 1024;
    if (RegOpenKeyEx(HKEY_LOCAL_MACHINE, "System\CurrentControlSet\Control\Session Manager\Environment", 0, KEY_READ | KEY_WRITE, &key) != ERROR_SUCCESS)
    {
        RegCloseKey(key);
    }
    else
    {
        if (RegQueryValueEx(key, "SERVIDOR_DIR", NULL, NULL, (LPBYTE)&appPath, &appPathLength) != ERROR_FILE_NOT_FOUND)
        {
            HANDLE hFile;
            string dateProv = getDate();
            char *date = new char[dateProv.size() + 1];
            copy(dateProv.begin(), dateProv.end(), date);
            date[dateProv.size()] = '';
            char fileNamePath[MAX_PATH];
            strcpy(fileNamePath, appPath);
            strcat(fileNamePath, "\logs\painel\");
            strcat(fileNamePath, date);
            strcat(fileNamePath, "levaetraz.log");
            puts(fileNamePath);
            hFile = CreateFile(
                fileNamePath,           // file to open
                GENERIC_WRITE,          // open for writing
                0,                      // share for writing
                NULL,                   // default security
                //  CREATE_NEW,         // existing file only
                //CREATE_ALWAYS,        // creates a new file, always.
                OPEN_ALWAYS,            // creates a new file, always.
                FILE_ATTRIBUTE_NORMAL,  // normal file
                NULL                    // no attr. template
                );
            if (hFile != INVALID_HANDLE_VALUE)
            {
                // Write to File
                BOOL bErrorFlag = FALSE;
                string hourProv = getHour();
                char *hour = new char[hourProv.size() + 1];
                copy(hourProv.begin(), hourProv.end(), hour);
                hour[hourProv.size()] = '';
                char stringLog[1024];
                strcpy(stringLog, hour);
                strcat(stringLog, &s[0]);
                strcat(stringLog, "rn");
                puts(stringLog);
                DWORD dwPtr = SetFilePointer(hFile, 0, NULL, FILE_END); //set pointer position to end file
                DWORD dwBytesToWrite = lstrlen(stringLog);
                DWORD a = 0;
                bErrorFlag = WriteFile(
                    hFile,              // open file handle
                    stringLog,          // start of data to write
                    dwBytesToWrite,     // number of bytes to write
                    &dwPtr,             // number of bytes that were written
                    NULL                // no overlapped structure
                    );
                delete[] hour;
            }
            delete[] date;
            CloseHandle(hFile);
            RegCloseKey(key);
        }
        RegCloseKey(key);
    }
}

在我把可变参数数量的可能性和调用日志("任何东西")的工作，那么这将如何在log.cpp与可变参数数量的工作?

void log(char *log)
{
    HANDLE hFile;
    std::string dateProv = getDate();
    char *date = new char[dateProv.size() + 1];
    std::copy(dateProv.begin(), dateProv.end(), date);
    date[dateProv.size()] = '';
    char fileNamePath[MAX_PATH];
    strcpy(fileNamePath, "logs/painel/");
    strcat(fileNamePath, date);
    strcat(fileNamePath, "levaetraz.log");
    puts(fileNamePath);
    hFile = CreateFile(
        fileNamePath,           // file to open
        GENERIC_WRITE,          // open for writing
        0,                      // share for writing
        NULL,                   // default security
        //  CREATE_NEW,         // existing file only
        //CREATE_ALWAYS,        // creates a new file, always.
        OPEN_ALWAYS,            // creates a new file, always.
        FILE_ATTRIBUTE_NORMAL,  // normal file
        NULL                    // no attr. template
        );
    if (hFile != INVALID_HANDLE_VALUE)
    {
        // Write to File
        BOOL bErrorFlag = FALSE;
        std::string hourProv = getHour();
        char *hour = new char[hourProv.size() + 1];
        std::copy(hourProv.begin(), hourProv.end(), hour);
        hour[hourProv.size()] = '';
        char stringLog[1024];
        strcpy(stringLog, hour);
        strcat(stringLog, log);
        strcat(stringLog, "rn");
        puts(stringLog);
        DWORD dwPtr = SetFilePointer(hFile, 0, NULL, FILE_END); //set pointer position to end file
        DWORD dwBytesToWrite = lstrlen(stringLog);
        DWORD a = 0;
        bErrorFlag = WriteFile(
            hFile,              // open file handle
            stringLog,          // start of data to write
            dwBytesToWrite,     // number of bytes to write
            &dwPtr,             // number of bytes that were written
            NULL                // no overlapped structure
            );
        delete[] hour;
    }
    delete[] date;
    CloseHandle(hFile);
}

我已经创建了一个log.h并包含在main.cpp

#pragma once
template<typename... Args>
void log(Args... a_args);

缺少什么?