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// initializing a (waitd to the essentials) singleton, using std::once_flag.
// don't forget -pthread
#include <iostream>
#include <mutex>
struct Single
{
static Single *s_single;
static std::once_flag s_resourceFlag;
static void initialize()
{
std::cout << "initializing\n";
s_single = new Single;
}
static Single *instance()
{
std::call_once(s_resourceFlag, initialize);
return s_single;
}
};
Single *Single::s_single;
std::once_flag Single::s_resourceFlag;
int main()
{
Single::instance();
Single::instance();
}
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