compat.concurrentqueue

// compat.concurrentqueue `c-api` feature — drive the flat extern "C" surface
// over both queues. Values cross the boundary as void*, so the test round-trips
// integers through MoodycamelValue and checks them on the way out. A package
// that compiled the wrappers against the wrong queue type (cq vs bcq handles
// are both void*) would still link and swap semantics — which is exactly the
// failure these assertions catch.
#include <c_api/concurrentqueue.h>

#include <cstdio>
#include <stdint.h>

int main() {
    bool ok = true;
    auto check = [&](bool cond, const char* what) {
        if (!cond) {
            std::printf("FAIL: %s\n", what);
            ok = false;
        }
    };

    // ---- plain queue -------------------------------------------------------
    {
// …