[C++]vsprintf to std::vector<char>

vsprintfToVector.cpp

#include <vector>   // std::vector
#include <stdarg.h> // va_list, va_start, va_end, va_copy

size_t getVsprintfByteLength(const char *fmt, va_list vlist) {
    va_list tmpVlist;
    va_copy(tmpVlist, vlist);
    size_t const byteLength = vsnprintf(nullptr, 0, fmt, tmpVlist);
    va_end(tmpVlist);
    return byteLength;
}

std::vector<char> vsprintfToVector(const char *fmt, va_list vlist) {
    std::vector<char> buf(1 + getVsprintfByteLength(fmt, vlist));
    vsnprintf(buf.data(), buf.size(), fmt, vlist);
    return buf;
}

std::vector<char> sprintfToVector(const char *fmt, ...) {
    va_list vlist;
    va_start(vlist, fmt);
    std::vector<char> buf = vsprintfToVector(fmt, vlist);
    va_end(vlist);
    return buf;
}

int main() {
    std::vector<char> const vec = sprintfToVector("%s, %s!", "Hello", "world");
    printf("%.*s\n", static_cast<unsigned>(vec.size()), vec.data());
}