int mbsinit( const mbstate_t* ps);

#include 
#include 
#include 
using namespace std;

void test_ps(mbstate_t ps)
{
    if (mbsinit(&ps))
    cout << "the conversion state is initial conversion state" << endl;
    else
    cout << "the conversion state is not initial conversion state" << endl;
}

int main()
{
    setlocale(LC_ALL, "en_US.utf8");
    
    char str[] = "\u00b5";
    mbstate_t ps = mbstate_t();
    
    cout << "Initially after creating ps, ";
    test_ps(ps);
    mbrlen(str, 1, &ps);
    
    cout << "After performing some task, ";
    test_ps(ps);
    
    return 0;
}

Initially after creating ps, the conversion state is initial conversion state
After performing some task, the conversion state is not initial conversion state