Solved

std::list  .size method

Posted on 2012-03-17
6
474 Views
Last Modified: 2012-03-18
I have seen sometimes core files in my application and when I bactraced I found it is coring at executing .size() function on std::list

std::list<std::string> myStringList

myStringList.size() sometimes cores

myStringList is member of static class which has only one instance for the entire application. I understand it should be protected by lock which I am not doing but could .size() on list ever core?
0
Comment
Question by:learningunix
[X]
Welcome to Experts Exchange

Add your voice to the tech community where 5M+ people just like you are talking about what matters.

  • Help others & share knowledge
  • Earn cash & points
  • Learn & ask questions
  • 3
  • 3
6 Comments
 
LVL 53

Expert Comment

by:Infinity08
ID: 37732911
Many things can cause a core dump given the right (or better : wrong) set of circumstances.

What kind of core dump is it ?

Is there a possibility of memory corruption ?

Since you mentioned locking, are multiple threads trying to access the list ?
0
 

Author Comment

by:learningunix
ID: 37733004
I was looking more into the code, I was having lock when I add entry to the list but when retrieving the size() I don't lock it. Could this cause the core?

Based on my design, yes it is possible one thread can update the list while I am trying to retrieve the size() of the list by other thread

Here's what I see when it execute size() on the list.

Program terminated with signal 11, Segmentation fault.
#0  0x00007f219fff95b1 in std::_List_const_iterator<string*>::operator++ (this=0x7f21ab5e8f58) at /usr/include/c++/4.3/bits/stl_list.h:221
221             _M_node = _M_node->_M_next;
(gdb) bt
#0  0x00007f219fff95b1 in std::_List_const_iterator<string*>::operator++ (this=0x7f21ab5e8f58) at /usr/include/c++/4.3/bits/stl_list.h:221
#1  0x00007f219fff95e4 in std::__distance<std::_List_const_iterator<string*> > (__first=..., __last=...) at /usr/include/c++/4.3/bits/stl_iterator_base_funcs.h:84
#2  0x00007f219fff962d in std::distance<std::_List_const_iterator<string*> > (__first=..., __last=...) at /usr/include/c++/4.3/bits/stl_iterator_base_funcs.h:119
0
 
LVL 53

Expert Comment

by:Infinity08
ID: 37733030
>> it is possible one thread can update the list while I am trying to retrieve the size() of the list by other thread

Then that's a big suspect :)

You will need some way of ensuring this doesn't happen, and proper locking is one such way.
0
Independent Software Vendors: We Want Your Opinion

We value your feedback.

Take our survey and automatically be enter to win anyone of the following:
Yeti Cooler, Amazon eGift Card, and Movie eGift Card!

 

Author Comment

by:learningunix
ID: 37733218
hmmm... I thought executing .size() on list is just a passive command and this should be ok. looks like my assumption is wrong
0
 
LVL 53

Accepted Solution

by:
Infinity08 earned 200 total points
ID: 37734230
A std::list is a linked list. Calculating the size of a linked list is not "passive", but involves traversing all nodes in the list.
0
 

Author Closing Comment

by:learningunix
ID: 37734757
Thanks a lot.
0

Featured Post

Independent Software Vendors: We Want Your Opinion

We value your feedback.

Take our survey and automatically be enter to win anyone of the following:
Yeti Cooler, Amazon eGift Card, and Movie eGift Card!

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Suggested Solutions

What is C++ STL?: STL stands for Standard Template Library and is a part of standard C++ libraries. It contains many useful data structures (containers) and algorithms, which can spare you a lot of the time. Today we will look at the STL Vector. …
Container Orchestration platforms empower organizations to scale their apps at an exceptional rate. This is the reason numerous innovation-driven companies are moving apps to an appropriated datacenter wide platform that empowers them to scale at a …
The goal of the video will be to teach the user the difference and consequence of passing data by value vs passing data by reference in C++. An example of passing data by value as well as an example of passing data by reference will be be given. Bot…
The viewer will be introduced to the technique of using vectors in C++. The video will cover how to define a vector, store values in the vector and retrieve data from the values stored in the vector.

756 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question