如何malloc（）函数会导致SIGSEGV？ [英] How can malloc() cause a SIGSEGV?

问题描述

我在我的节目一个奇怪的错误，它似乎我的malloc（）是导致SIGSEGV，其中就我的理解去没有任何意义。我使用了一个名为simclist动态列表库。

I have an odd bug in my program, it appears to me that malloc() is causing a SIGSEGV, which as far as my understanding goes does not make any sense. I am using a library called simclist for dynamic lists.

下面是以后引用一个结构：

Here is a struct that is referenced later:

typedef struct {
    int msgid;
    int status;
    void* udata;
    list_t queue;
} msg_t;

这里是code：

And here is the code:

msg_t* msg = (msg_t*) malloc( sizeof( msg_t ) );

msg->msgid = msgid;
msg->status = MSG_STAT_NEW;
msg->udata = udata;
list_init( &msg->queue );

list_init 是程序失败，这里是code为list_init：

list_init is where the program fails, here is the code for list_init:

/* list initialization */
int list_init(list_t *restrict l) {
    if (l == NULL) return -1;

    srandom((unsigned long)time(NULL));

    l->numels = 0;

    /* head/tail sentinels and mid pointer */
    l->head_sentinel = (struct list_entry_s *)malloc(sizeof(struct list_entry_s));
    l->tail_sentinel = (struct list_entry_s *)malloc(sizeof(struct list_entry_s));
    l->head_sentinel->next = l->tail_sentinel;
    l->tail_sentinel->prev = l->head_sentinel;
    l->head_sentinel->prev = l->tail_sentinel->next = l->mid = NULL;
    l->head_sentinel->data = l->tail_sentinel->data = NULL;

    /* iteration attributes */
    l->iter_active = 0;
    l->iter_pos = 0;
    l->iter_curentry = NULL;

    /* free-list attributes */
    l->spareels = (struct list_entry_s **)malloc(SIMCLIST_MAX_SPARE_ELEMS * sizeof(struct list_entry_s *));
    l->spareelsnum = 0;

#ifdef SIMCLIST_WITH_THREADS
    l->threadcount = 0;
#endif

    list_attributes_setdefaults(l);

    assert(list_repOk(l));
    assert(list_attrOk(l));

    return 0;
}

行 1-方式＆gt; spareels =（结构list_entry_s **）的malloc（SIMCLIST_MAX_SPARE_ELEMS * 是SIGSEGV是根据堆栈跟踪引起我用gdb / nemiver进行调试，但很茫然。第一次调用这个函数时它工作正常，但总是失败，第二次，怎么能malloc（）函数会导致SIGSEGV？

the line l->spareels = (struct list_entry_s **)malloc(SIMCLIST_MAX_SPARE_ELEMS * is where the SIGSEGV is caused according to the stack trace. I am using gdb/nemiver for debugging but am at a loss. The first time this function is called it works fine but it always fails the second time. How can malloc() cause a SIGSEGV?

这是堆栈跟踪：

#0  ?? () at :0
#1  malloc () at :0
#2  list_init (l=0x104f290) at src/simclist.c:205
#3  msg_new (msg_switch=0x1050dc0, msgid=8, udata=0x0) at src/msg_switch.c:218
#4  exread (sockfd=8, conn_info=0x104e0e0) at src/zimr-proxy/main.c:504
#5  zfd_select (tv_sec=0) at src/zfildes.c:124
#6  main (argc=3, argv=0x7fffcabe44f8) at src/zimr-proxy/main.c:210

任何帮助或洞察力是非常AP preciated！

Any help or insight is very appreciated!

推荐答案

的malloc 当堆已损坏，例如段错误。检查你是不是写任何东西超出任何previous分配的范围。

malloc can segfault for example when the heap is corrupted. Check that you are not writing anything beyond the bounds of any previous allocation.

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