How to create a std::ofstream to a temp file

warning: the use of `tmpnam' is dangerous, better use `mkstemp'

char *tmpname = strdup("/tmp/tmpfileXXXXXX");
    ofstream f;
    int fd = mkstemp(tmpname);
    f.attach(fd);

char *tmpname = strdup("/tmp/tmpfileXXXXXX");
mkstemp(tmpname);
ofstream f(tmpname);

#include <stdlib.h>
#include <fstream>
#include <iostream>
#include <vector>

std::string open_temp(std::string path, std::ofstream& f) {
    path += "/XXXXXX";
    std::vector<char> dst_path(path.begin(), path.end());
    dst_path.push_back('');

    int fd = mkstemp(&dst_path[0]);
    if(fd != -1) {
        path.assign(dst_path.begin(), dst_path.end() - 1);
        f.open(path.c_str(),
               std::ios_base::trunc | std::ios_base::out);
        close(fd);
    }
    return path;
}

int main() {
    std::ofstream logfile;
    open_temp("/tmp", logfile);
    if(logfile.is_open()) {
        logfile << "hello, dude" << std::endl;
    }
}

char tmpname[256];
ofstream f;
sprintf (tmpname, "/tmp/tmpfileXXXX");
int fd = mkstemp(tmpname);
ofstream f(tmpname);