Valgrind抱怨数据可能丢失

Valgrind complains data possibly lost

本文关键字：数据 Valgrind      更新时间：2023-10-16

我在c++中有一个回调函数，它做的是:

void MasterInterface::zsock_cb(struct ev_loop *loop, ev_zsock_t *wz, int revents) {
    char iden[MAX_MSG_LEN];
    char msg[MAX_MSG_LEN];
    int numIDBytes = zmq_recv(wz->zsock, iden, sizeof(iden), 0);
    int numBytes = zmq_recv(wz->zsock, msg, sizeof(msg), 0);
    masterStruct* mStruct = (masterStruct*)wz->data;
    std::string idenData = std::string(static_cast<char*>(iden), numIDBytes);
    std::string msgData = std::string(static_cast<char*>(msg), numBytes);
    cout << "[IN] " << msgData << endl;
    if (!mStruct->synchronized) {
        if (!IDRegistered(mStruct, idenData)) {
            cout << "[IN] " << idenData << endl;
            cout << "[IN] " << msgData << endl;
            mStruct->slaveIDs[mStruct->counter++] = idenData;
            zmq_send (wz->zsock, idenData.c_str(), idenData.size(), ZMQ_SNDMORE);
            zmq_send (wz->zsock, msgData.c_str(), msgData.size(), 0);
        }
            if (mStruct->counter==SLAVES_EXPECTED) {
                sendCommand(wz,"Master connected to slaves.");
                mStruct->synchronized = true;
            }
    }
}
bool MasterInterface::IDRegistered(masterStruct* mStruct, const std::string& id) {
    for (int i=0; i < SLAVES_EXPECTED; i++) {
        if (mStruct->slaveIDs[i]=="") continue;
        if (mStruct->slaveIDs[i].compare(id)==0)
            return true;
    }
    return false;
}

我在程序上运行valgrind，它报告3块中的87字节可能丢失，表明这是数据"可能丢失"的行。std::string identidata = std::string(static_cast(identity)， numIDBytes);

我不认为我做错了什么，为什么valgrind抱怨?这是假阳性吗?

谢谢。

这是mstruct。

struct masterStruct {
public:
    int counter;
    bool synchronized;
    std::string slaveIDs[3];
};

编译没有优化。o0

下面是valgrind消息:

^C[Signal Caught] Closing connections...
Exited Master Process...
==6606== 
==6606== HEAP SUMMARY:
==6606==     in use at exit: 143 bytes in 4 blocks
==6606==   total heap usage: 5,866 allocs, 5,862 frees, 533,480 bytes allocated
==6606== 
==6606== Searching for pointers to 4 not-freed blocks
==6606== Checked 239,000 bytes
==6606== 
==6606== 87 bytes in 3 blocks are possibly lost in loss record 2 of 2
==6606==    at 0x4A074CC: operator new(unsigned long) (vg_replace_malloc.c:298)
==6606==    by 0x3A7CC9C3C8: std::string::_Rep::_S_create(unsigned long, unsigned long, std::allocator<char> const&) (in /usr/lib64/libstdc++.so.6.0.13)
==6606==    by 0x3A7CC9CDE4: ??? (in /usr/lib64/libstdc++.so.6.0.13)
==6606==    by 0x3A7CC9CF6A: std::basic_string<char, std::char_traits<char>, std::allocator<char> >::basic_string(char const*, unsigned long, std::allocator<char> const&) (in /usr/lib64/libstdc++.so.6.0.13)
==6606==    by 0x402FD5: MasterInterface::zsock_cb(ev_loop*, ev_zsock_t*, int) (MasterInterface.cpp:74)
==6606==    by 0x404C6B: s_check_cb (ev_zsock.c:61)
==6606==    by 0x4E872BC: ev_invoke_pending (ev.c:3155)
==6606==    by 0x4E8BAE1: ev_run (ev.c:3555)
==6606==    by 0x403423: MasterInterface::init() (MasterInterface.cpp:118)
==6606==    by 0x4046DB: main (PXSMaster.cpp:29)
==6606== 
==6606== LEAK SUMMARY:
==6606==    definitely lost: 0 bytes in 0 blocks
==6606==    indirectly lost: 0 bytes in 0 blocks
==6606==      possibly lost: 87 bytes in 3 blocks
==6606==    still reachable: 56 bytes in 1 blocks
==6606==         suppressed: 0 bytes in 0 blocks
==6606== Reachable blocks (those to which a pointer was found) are not shown.
==6606== To see them, rerun with: --leak-check=full --show-reachable=yes
==6606== 
==6606== ERROR SUMMARY: 1 errors from 1 contexts (suppressed: 4 from 4)
--6606-- 
--6606-- used_suppression:      4 U1004-ARM-_dl_relocate_object
==6606== 
==6606== ERROR SUMMARY: 1 errors from 1 contexts (suppressed: 4 from 4)
bash-4.1$

@Dark Falcon是正确的。

MasterInterface类被声明为一个全局变量。在这个类中，有 
struct masterStruct masStruct;

，其中有3个std::string数组。

这就是问题所在。当我按Ctrl-C时，valgrind可能没有考虑全局变量，因此这些字节可能会丢失。

将MasterInterface声明放在main()中解决了可能丢失的错误。

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