Question

我尝试获取0mq消息的单个部分，它的工作方式与预期的一样。然而，如果我用valgrind测试程序，我得到：

== 9436 ==条件跳转或移动取决于未初始化的值

== 9436 ==在0x4C2E128：strlen（在/usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so中）

== 9436 == by 0x401023：main（werft.c：73）

== 9436 ==

== 9436 ==条件跳转或移动取决于未初始化的值

== 9436 ==在0x4C2E128：strlen（在/usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so中）

== 9436 == by 0x401048：main（werft.c：74）

== 9436 ==

== 9436 ==条件跳转或移动取决于未初始化的值

== 9436 ==在0x4C2E128：strlen（在/usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so中）

== 9436 == by 0x538B7F9：vfprintf（在/usr/lib/libc-2.25.so中）

== 9436 == by 0x53B246F：vsnprintf（在/usr/lib/libc-2.25.so中）

== 9436 == by 0x5391F5E：snprintf（在/usr/lib/libc-2.25.so中）

== 9436 == by 0x40106F：main（werft.c：74）

我的代码是：

#define DEVICE_IDENTITY "de.logicway.pferdepflug" 


int main()
{


    char *incoming[2];

    void *context = zmq_ctx_new();

    void *responder = zmq_socket(context, ZMQ_ROUTER);
    zmq_bind(responder, "tcp://127.0.0.1:9990");


    void *requester = zmq_socket(context, ZMQ_DEALER);
    zmq_setsockopt(requester, ZMQ_IDENTITY, DEVICE_IDENTITY, strlen(DEVICE_IDENTITY));
    zmq_connect(requester, "tcp://127.0.0.1:9990");

    zmq_send(requester, "testfahrt", 9, 0);

    zmq_msg_t received;
    zmq_msg_init(&received);

    int i = 0;
    do {      


        int size = zmq_msg_recv(&received, responder, 0);
        char *buffer = (char*) zmq_msg_data(&received);
        incoming[i] = (char*) malloc(strlen(buffer) +1 * sizeof(char*));
        snprintf(incoming[i], strlen(buffer) +1, "%s", buffer);

        i++;

    } while(zmq_msg_more(&received));


    printf("Identifier: %s\n", incoming[0]);
    printf("Message: %s\n", incoming[1]);    

    free(incoming[0]);
    free(incoming[1]);

    zmq_msg_close(&received);
    zmq_close(requester);
    zmq_close(responder);
    zmq_ctx_destroy(context);
    return 0; 
}

（这不会像现在这样投入生产，只是让我理解0mq）

由于代码有效，并且＃34;罚款＆＃34;实际上，单位化值可能没有问题。但是，它仍困扰着我。

问题/ S：

在这种情况下，它应该打扰我吗？（是的，我知道，它通常应该正常;））
并且是收到的zmq_msg_t中所有麻烦的来源; / zmq_msg_init（安培;收到）;一部分？
如果没有，它在哪里以及如何解决？

非常感谢您的帮助！

Answer 1

第1部分：

Valgrind提到strlen正在使用未初始化的内存。在您的情况下，参数是buffer，它是从zmq库中检索的。

也许你应该检查所涉及的函数调用的返回值。

编辑：我使用了错误的API函数。删除了这部分。

第2部分：

正如已经提到的，你也搞砸了你的分配：

incoming[i] = (char*) malloc(strlen(buffer) +1 * sizeof(char*));

您不需要char *类型的元素，只需要char。 +1属于长度：

incoming[i] = (char*) malloc((strlen(buffer) +1) * sizeof(char));

鉴于sizeof (char)被定义为1且规则不能转换malloc的返回值，我们得到了这个：

incoming[i] = malloc(strlen(buffer) + 1);

下一步是从buffer复制字符串：

snprintf(incoming[i], strlen(buffer) +1, "%s", buffer);

鉴于您刚刚分配了足够的内存（可能会添加NULL检查），使用snprintf并没有太大的好处。您只需使用strcpy或只需一步创建strdup的副本

即可

Answer 2

看起来这是ZeroMQ错误。我的输出有--track-origins=yes valgrind选项：

[ ~]$ valgrind --track-origins=yes ./a.out 
==5272== Memcheck, a memory error detector
==5272== Copyright (C) 2002-2015, and GNU GPL'd, by Julian Seward et al.
==5272== Using Valgrind-3.12.0 and LibVEX; rerun with -h for copyright info
==5272== Command: ./a.out
==5272== 
==5272== Conditional jump or move depends on uninitialised value(s)
==5272==    at 0x4C30BC8: strlen (vg_replace_strmem.c:454)
==5272==    by 0x400C52: main (111.c:31)
==5272==  Uninitialised value was created by a stack allocation
==5272==    at 0x4E860B0: zmq::stream_engine_t::mechanism_ready() (stream_engine.cpp:793)
==5272== 
==5272== Conditional jump or move depends on uninitialised value(s)
==5272==    at 0x4C30BC8: strlen (vg_replace_strmem.c:454)
==5272==    by 0x400C77: main (111.c:32)
==5272==  Uninitialised value was created by a stack allocation
==5272==    at 0x4E860B0: zmq::stream_engine_t::mechanism_ready() (stream_engine.cpp:793)
==5272== 
==5272== Conditional jump or move depends on uninitialised value(s)
==5272==    at 0x4C30BC8: strlen (vg_replace_strmem.c:454)
==5272==    by 0x50FAAD0: vfprintf (vfprintf.c:1637)
==5272==    by 0x5123488: vsnprintf (vsnprintf.c:114)
==5272==    by 0x51017B1: snprintf (snprintf.c:33)
==5272==    by 0x400C9E: main (111.c:32)
==5272==  Uninitialised value was created by a stack allocation
==5272==    at 0x4E860B0: zmq::stream_engine_t::mechanism_ready() (stream_engine.cpp:793)
==5272== 
Identifier: de.logicway.pferdepflug
Message: testfahrt
==5272== 
==5272== HEAP SUMMARY:
==5272==     in use at exit: 0 bytes in 0 blocks
==5272==   total heap usage: 210 allocs, 210 frees, 271,368 bytes allocated
==5272== 
==5272== All heap blocks were freed -- no leaks are possible
==5272== 
==5272== For counts of detected and suppressed errors, rerun with: -v
==5272== ERROR SUMMARY: 6 errors from 3 contexts (suppressed: 0 from 0)

未初始化的值来自stream_engine.cpp:793，因此可能会向ZeroMQ bug tracker报告。

ZeroMQ

2 个答案:

第1部分：

第2部分：