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.
Here is a struct that is referenced later:
typedef struct {
int msgid;
int status;
void* udata;
list_t queue;
} msg_t;
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
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;
}
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?
This is the stack trace:
#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
Any help or insight is very appreciated!