std::sprintf to std::string

strprintf.cpp

#include <cerrno>
#include <cstring>
#include <iostream>
#include <string>
#include <utility>

template <typename... Args>
std::string strprintf(Args&&... args) {
    std::string s;
    const std::size_t sso = s.capacity();
    s.resize(sso);
    const int res1 = std::snprintf(&s[0], sso, std::forward<Args>(args)...);
    if (res1 < 0) return "";
    s.resize(res1);
    if (static_cast<std::size_t>(res1) > sso) {
        const int res2 =
            std::snprintf(&s[0], s.size(), std::forward<Args>(args)...);
        if (res2 != res1) return "";
    }
    return s;
}