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#include <atomic>

typedef void (*fptr)(int);
typedef std::atomic<fptr> atomicfptr;

void testfunction(int) { }

void test(volatile atomicfptr &a)
{
    fptr v = a.load(std::memory_order_acquire);
    while (!a.compare_exchange_strong(v, &testfunction,
                                      std::memory_order_acq_rel,
                                      std::memory_order_acquire)) {
        v = a.exchange(&testfunction);
    }

    a.store(&testfunction, std::memory_order_release);
}

int main(int, char **)
{
    atomicfptr fptr(testfunction);
    test(fptr);
    return 0;
}