*** glibc detected *** error

[bscranda]

I've narrowed down my problematic function to the one below:

void SortedType::InsertItem(ItemType item)
{
  NodeType* newNode;  // pointer to node being inserted
  NodeType* predLoc;  // trailing pointer
  NodeType* location; // traveling pointer
  bool moreToSearch;

  location = listData;
  predLoc = NULL;
  moreToSearch = (location != NULL);

  // Find insertion point.
  while (moreToSearch)
  {
    if(item.ComparedTo(location->info) == GREATER)
    {
      predLoc = location;
      location = location->next;
      moreToSearch = (location != NULL);
    }
    else
      moreToSearch = false;
  }

  // Prepare node for insertion
  newNode = new NodeType;
  newNode->info = item;

  // Insert node into list.
  if (predLoc == NULL)         // Insert as first
  {
    newNode->next = listData;
    listData = newNode;
    newNode->next = listData;
    listData = newNode;
  }
  else
  {
    newNode->next = location;
    predLoc->next = newNode;
  }
  length++;
}

Error message:

*** glibc detected *** ./a.out: double free or corruption (fasttop): 0x0000000000608500 ***
======= Backtrace: =========
/lib64/libc.so.6[0x7f918a0a50c8]
/lib64/libc.so.6(cfree+0x76)[0x7f918a0a6c26]
./a.out[0x4015a2]
./a.out[0x4015d1]
./a.out[0x4010fc]
/lib64/libc.so.6(__libc_start_main+0xe6)[0x7f918a04f586]
./a.out[0x400e09]
======= Memory map: ========
00400000-00403000 r-xp 00000000 08:11 385682                             /home/abc/bscranda/cs216/p7/a.out
00602000-00603000 r--p 00002000 08:11 385682                             /home/abc/bscranda/cs216/p7/a.out
00603000-00604000 rw-p 00003000 08:11 385682                             /home/abc/bscranda/cs216/p7/a.out
00604000-00625000 rw-p 00604000 00:00 0                                  [heap]
7f9184000000-7f9184021000 rw-p 7f9184000000 00:00 0
7f9184021000-7f9188000000 ---p 7f9184021000 00:00 0
7f918a031000-7f918a180000 r-xp 00000000 08:02 12621                      /lib64/libc-2.9.so
7f918a180000-7f918a380000 ---p 0014f000 08:02 12621                      /lib64/libc-2.9.so
7f918a380000-7f918a384000 r--p 0014f000 08:02 12621                      /lib64/libc-2.9.so
7f918a384000-7f918a385000 rw-p 00153000 08:02 12621                      /lib64/libc-2.9.so
7f918a385000-7f918a38a000 rw-p 7f918a385000 00:00 0
7f918a38a000-7f918a3a0000 r-xp 00000000 08:02 12720                      /lib64/libgcc_s.so.1
7f918a3a0000-7f918a5a0000 ---p 00016000 08:02 12720                      /lib64/libgcc_s.so.1
7f918a5a0000-7f918a5a1000 r--p 00016000 08:02 12720                      /lib64/libgcc_s.so.1
7f918a5a1000-7f918a5a2000 rw-p 00017000 08:02 12720                      /lib64/libgcc_s.so.1
7f918a5a2000-7f918a5f7000 r-xp 00000000 08:02 110887                     /lib64/libm-2.9.so
7f918a5f7000-7f918a7f6000 ---p 00055000 08:02 110887                     /lib64/libm-2.9.so
7f918a7f6000-7f918a7f7000 r--p 00054000 08:02 110887                     /lib64/libm-2.9.so
7f918a7f7000-7f918a7f8000 rw-p 00055000 08:02 110887                     /lib64/libm-2.9.so
7f918a7f8000-7f918a8e9000 r-xp 00000000 08:02 32777                      /usr/lib64/libstdc++.so.6.0.10
7f918a8e9000-7f918aae8000 ---p 000f1000 08:02 32777                      /usr/lib64/libstdc++.so.6.0.10
7f918aae8000-7f918aaef000 r--p 000f0000 08:02 32777                      /usr/lib64/libstdc++.so.6.0.10
7f918aaef000-7f918aaf1000 rw-p 000f7000 08:02 32777                      /usr/lib64/libstdc++.so.6.0.10
7f918aaf1000-7f918ab04000 rw-p 7f918aaf1000 00:00 0
7f918ab04000-7f918ab22000 r-xp 00000000 08:02 11706                      /lib64/ld-2.9.so
7f918ad07000-7f918ad0a000 rw-p 7f918ad07000 00:00 0
7f918ad1f000-7f918ad21000 rw-p 7f918ad1f000 00:00 0
7f918ad21000-7f918ad22000 r--p 0001d000 08:02 11706                      /lib64/ld-2.9.so
7f918ad22000-7f918ad23000 rw-p 0001e000 08:02 11706                      /lib64/ld-2.9.so
7fffa7e62000-7fffa7e77000 rw-p 7ffffffe9000 00:00 0                      [stack]
7fffa7fff000-7fffa8000000 r-xp 7fffa7fff000 00:00 0                      [vdso]
ffffffffff600000-ffffffffff601000 r-xp 00000000 00:00 0                  [vsyscall]
Aborted

Totally lost here, can anyone help? I'm pretty much a c++ newb, so let me know if you need to see more of my program to help. Thanks!

[Peter87]

newNode->next = listData;
listData = newNode;
newNode->next = listData;
listData = newNode;

After this newNode->next will point to newNode and you lose track of the other nodes.

[bscranda]

Peter you're a life saver!! Can't believe that was my problem ><
Thanks again!

[andre04]

I'm getting the same error too but i don't know what method is causing it. What's the point of this error? why does it show up?

[LB]

It shows up to let you know you're doing something wrong that, if it had not been detected, would have caused serious problems (eg segfault, memory corruption/leak, etc)