程式連結了DPDK庫，啟動就出錯，打出如下資訊：

EAL: UIO_RESOURCE_LIST tailq is already registered
PANIC in tailqinitfn_rte_uio_tailq():
Cannot initialize tailq: UIO_RESOURCE_LIST

分析發現，C語言定義constructor屬性的函式會先於main()執行，DPDK中定義了RTE_INIT()巨集，用來宣告一個如建構函式:

#define RTE_PRIO(prio) \
    RTE_PRIORITY_ ## prio

/**
 * Run function before main() with high priority.
 *
 * @param func
 *   Constructor function.
 * @param prio
 *   Priority number must be above 100.
 *   Lowest number is the first to run.
 
 
*/
#ifndef RTE_INIT_PRIO /* Allow to override from EAL */
#define RTE_INIT_PRIO(func, prio) \
static void __attribute__((constructor(RTE_PRIO(prio)), used)) func(void)
#endif

/**
 * Run function before main() with low priority.
 *
 * The constructor will be run after prioritized constructors.
 *
 * @param func
 *   Constructor function.
 
 
*/
#define RTE_INIT(func) \
    RTE_INIT_PRIO(func, LAST)

在tailq.h中定義了EAL_REGISTER_TAILQ()

/**
 * Register a tail queue.
 *
 * Register a tail queue from shared memory.
 * This function is mainly used by EAL_REGISTER_TAILQ macro which is used to
 * register tailq from the different dpdk libraries. Since this macro is a
 * constructor, the function has no access to dpdk shared memory, so the
 * registered tailq can not be used before call to rte_eal_init() which calls
 * rte_eal_tailqs_init().
 *
 * @param t
 *   The tailq element which contains the name of the tailq you want to
 *   create (/retrieve when in secondary process).
 * @return
 *   0 on success or -1 in case of an error.
 
 
*/
int rte_eal_tailq_register(struct rte_tailq_elem *t);

#define EAL_REGISTER_TAILQ(t) \
RTE_INIT(tailqinitfn_ ##t) \
{ \
    if (rte_eal_tailq_register(&t) < 0) \
        rte_panic("Cannot initialize tailq: %s\n", t.name); \
}

然後用定義了很多初始化建構函式，比如rte_ring.c中:

#define RTE_TAILQ_RING_NAME "RTE_RING"

static struct rte_tailq_elem rte_ring_tailq = {
    .name = RTE_TAILQ_RING_NAME,
};
EAL_REGISTER_TAILQ(rte_ring_tailq)

所以原因是涉及到的constructor函式程式碼有多個例項，被重複呼叫。我遇到的例項是因為有重複靜態連結：app連結了libxxx.a和librte_*.a,並且libxxx.a也連結了librte_*.a，app裡面就有兩份librte_*.a的程式碼例項。

解決方法：把靜態連結librte_*.a都改成動態連結librte_*.so

加入log，可發現在main()函式之前呼叫了很多EAL_REGISTER_TAILQ()函式:

EAL: rte_eal_tailq_register: name=RTE_RING
EAL: rte_eal_tailq_register: name=RTE_MEMPOOL
EAL: rte_eal_tailq_register: name=RTE_MBUF_DYNFIELD
EAL: rte_eal_tailq_register: name=RTE_MBUF_DYNFLAG
EAL: rte_eal_tailq_register: name=RTE_HASH
EAL: rte_eal_tailq_register: name=RTE_FBK_HASH
EAL: rte_eal_tailq_register: name=RTE_THASH
EAL: rte_eal_tailq_register: name=RTE_ACL
EAL: rte_eal_tailq_register: name=RTE_DIST_BURST
EAL: rte_eal_tailq_register: name=RTE_DISTRIBUTOR
EAL: rte_eal_tailq_register: name=RTE_EFD
EAL: rte_eal_tailq_register: name=RTE_KNI
EAL: rte_eal_tailq_register: name=RTE_LPM
EAL: rte_eal_tailq_register: name=RTE_LPM6
EAL: rte_eal_tailq_register: name=RTE_MEMBER
EAL: rte_eal_tailq_register: name=RTE_RIB
EAL: rte_eal_tailq_register: name=RTE_RIB6
EAL: rte_eal_tailq_register: name=RTE_REORDER
EAL: rte_eal_tailq_register: name=RTE_STACK
EAL: rte_eal_tailq_register: name=RTE_IPSEC_SAD
EAL: rte_eal_tailq_register: name=RTE_FIB
EAL: rte_eal_tailq_register: name=RTE_FIB6