Re: Segementation Fault

[sai gautams]

Hi all,

I hope you are well. In my ndnSIM I tried creating an on-off application by changing the frequencies in the consumerHelper. When I try building I get a segmentation fault related to ns-3 ptr. Can anyone please explain to me the fault I'm getting.If anyone can help recognizing the fault in my code that would be helpful.   

Program received signal SIGSEGV, Segmentation fault.

0x00007ffff7f555ba in ns3::Ptr<ns3::NetDevice>::Ptr (this=0xf800005555556b8f, o=...) at ./ns3/ptr.h:741
741      : m_ptr (PeekPointer (o))

[Tom Henderson]

gdb may shed some light on the invalid pointer that you appear to have.
Please look at:
https://www.nsnam.org/wiki/HOWTO_use_gdb_to_debug_program_errors

- Tom

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[Bharat Agarwal]

U are trying to retrieve data from memory which has not assigned.

Possibly due to assigning more number of UEs but not using them or same for BS.

This error is something related to zero pointer.

Share ur code please 

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[sai gautams]

Here's the code please have a look.

#include "ns3/core-module.h"

#include "ns3/network-module.h"
#include "ns3/point-to-point-module.h"
#include "ns3/ndnSIM-module.h"
#include "assert.h"
namespace ns3 {

int
main(int argc, char* argv[])
{
  Config::SetDefault("ns3::PointToPointNetDevice::DataRate", StringValue("20Mbps"));
  Config::SetDefault("ns3::PointToPointChannel::Delay", StringValue("5ms"));
  Config::SetDefault("ns3::QueueBase::MaxSize", StringValue("50p"));

  CommandLine cmd;
  cmd.Parse(argc, argv);
 
  NodeContainer nodes;
  nodes.Create(5);
  for (int i=0;i<5;i++)
  {
  PointToPointHelper p2p;
  p2p.Install(nodes.Get(i),nodes.Get(i+1));
  }
  ndn::StackHelper ndnHelper;
  ndnHelper.setPolicy("nfd::cs::lru");
  ndnHelper.SetDefaultRoutes(true);
  ndnHelper.setCsSize(50);
  ndnHelper.InstallAll();
 
  ndn::StrategyChoiceHelper::InstallAll("/prefix", "/localhost/nfd/startegy/best-route");
 
  //ndn::GlobalRoutingHelper ndnGlobalRoutingHelper;
  //ndnGlobalRoutingHelper.InstallAll();
 
  // Consumer 1
  ndn::AppHelper consumerHelper("ns3::ndn::ConsumerCbr");
 
  consumerHelper.SetPrefix("/prefix");
  consumerHelper.SetAttribute("Frequency", StringValue("100"));
  auto Consumer1 = consumerHelper.Install(nodes.Get(0));                        
  Consumer1.Start(Seconds(2));
  Consumer1.Stop(Seconds(5));
 
  //Consumer 2
  consumerHelper.SetPrefix("/prefix");
  consumerHelper.SetAttribute("Frequency", StringValue("150"));
  auto Consumer2 = consumerHelper.Install(nodes.Get(1));                      
  Consumer2.Start(Seconds(0));
  Consumer2.Stop(Seconds(5));
 
  //Consumer 3
  consumerHelper.SetPrefix("/prefix");
  consumerHelper.SetAttribute("Frequency", StringValue("150"));
  auto Consumer3 = consumerHelper.Install(nodes.Get(2));                      
  Consumer3.Start(Seconds(3));
  Consumer3.Stop(Seconds(5));
 
  //Producer
  ndn::AppHelper producerHelper("ns3::ndn::Producer");
  producerHelper.SetPrefix("/prefix");
  producerHelper.SetAttribute("PayloadSize", StringValue("1024"));
  producerHelper.Install(nodes.Get(5));
 
//  ndn::GlobalRoutingHelper::CalculateRoutes();
 
  Simulator::Stop(Seconds(10.0));

  Simulator::Run();
  Simulator::Destroy();

  return 0;
}

} // namespace ns3

int
main(int argc, char* argv[])
{
  return ns3::main(argc, argv);
}
 

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--

Sai Gautam Mandapati

Deakin University

Doctor of Philosophy Student

[Bharat Agarwal]

U have initialized 5 nodes and only used 4.

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[sai gautams]

Thank you. Well, I tried creating another Consumer node. The problem still persists.So, there would be a total of 4 Consumers and 1 producer according to what I have declared as my number of nodes.But that is not solving the problem yet.

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--

Sai Gautam Mandapati

Deakin University

Doctor of Philosophy Student

Higher Degree by Research

Faculty of Science, Engineering and Built-in Environment

E-mail: saiga...@gmail.com

http://www.linkedin.com/in/sai-gautam-mandapati

[Bharat Agarwal]

 for (int i=0;i<5;i++)
  {
  PointToPointHelper p2p;
  p2p.Install(nodes.Get(i),nodes.Get(i+1));
  }

This loop is Wrong when i value will be 4 nodes.get(i+1) will take value 5 but u can go up to 0 1 2 3 4 only.

Please check this 

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[sai gautams]

Thank you so much for pointing this out. I solved the problem. When I'm trying to visualise the code, the following error shows up. I tried to debug but it exits the debugger normally.

/waf --run=ndn-onoff --vis

Waf: Entering directory `/home/smandapati/ndnSIM/ns-3/build'
Waf: Leaving directory `/home/smandapati/ndnSIM/ns-3/build'
Build commands will be stored in build/compile_commands.json
'build' finished successfully (1.077s)
Could not load plugin 'show_last_packets.py': No module named 'kiwi.ui'
Could not load icon applets-screenshooter due to missing gnomedesktop Python module
assert failed. cond="!m_metadataSkipped", msg="Error: attempting to enable the packet metadata subsystem too late in the simulation, which is not allowed.
A common cause for this problem is to enable ASCII tracing after sending any packets.  One way to fix this problem is to call ns3::PacketMetadata::Enable () near the beginning of the program, before any packets are sent.", file=../src/network/model/packet-metadata.cc, line=55

terminate called without an active exception

Command ['/home/smandapati/ndnSIM/ns-3/build/src/ndnSIM/examples/ns3-dev-ndn-onoff-debug', '--SimulatorImplementationType=ns3::VisualSimulatorImpl'] terminated with signal SIGIOT. Run it under a debugger to get more information (./waf --run <program> --command-template="gdb --args %s <args>").

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[Bharat Agarwal]

Try to run on gdb shell. SIGOT error usually comes when u havent intitlized anything and use it.

Best Regards ,

Bharat Agarwal 

Doctoral Researcher 

Dublin City University | School of Electronic Engineering

Glasnevin, Dublin 9 

Republic of Ireland 

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[sai gautams]

Thank you for your help Bharat. Can you please provide me with any useful links that provide information on how to run gdb shell. I'm only familiar with traditional gdb.

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[Bharat Agarwal]

just check doxygen.

U will find info their.

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