{

va_list copy;

va_copy(copy, args);

const int sz = vsnprintf(nullptr, 0, msg, args) + 1;

if (sz < 0) {

puts("error occurred during log formatting!\n");

va_end(copy);

return;

}

constexpr int max_stack_buffer_size = 512;

std::array<char, max_stack_buffer_size> buf;

char* out = buf.data();

if (sz >= max_stack_buffer_size) {

out = new char[sz];

}

vsnprintf(out, sz, msg, copy);

va_end(copy);

auto ms = std::chrono::duration_cast<std::chrono::milliseconds>(

std::chrono::high_resolution_clock::now().time_since_epoch());

printf("%s [%lld] %s %s\n", get_prefix(v), static_cast<long long>(ms.count()), tag, out);

// stdout is not line-buffered when redirected (for example to a file or to another process) so we must flush it

// manually.

fflush(stdout);

if (out != buf.data()) {

delete[] out;

}