Question

I am running two separate threads in C, both doing some operations. Both threads include infinite loop. When I run this program couple of times, I always get a memory leak error.

*** glibc detected *** ./a.out: free(): invalid next size (normal): 0x08652510 ***

======= Backtrace: =========

/lib/libc.so.6(+0x6c501)[0x3d1501]

...

I believe it is a memory error, the problem is, when I always need to stop that program(cause im still testing it), i just terminate the program with Ctrl+C, so I believe I always miss the free(anything) command, which then causes the error.

Can you tell me how to avoid this situation? So I can free() memory even in case I terminate the program?

Next thing which comes to my mind is, when i wait a couple of minutes and then run the program again, it runs perfectly again

Thanks for any hints

void *lineOne(void *dataO)
{
  struct IPlist *IPlist = dataO;

  static struct ARP_entryI ARP_tableI[ARP_TABLE_SIZE];
  int neigh=0; //pocet susedov
  int neigh1=0; //stav pred tym
  int i;

  getAddress();

  while(1)
  {
    while (neigh == neigh1)
    {
      neigh =rcvBroad(IPlist, neigh); 
    }

    neigh1=neigh;

    for (i=neigh ; i<neigh+1; i++)
    {
      main_client(ARP_tableI, IPlist[i-1].IPaddr); // vysle tcp, prijme arp
      getAddress();
    }
  }

}

//pocuvaServer, odpoveda ARP
void *lineTwo()
{
  static struct ARP_entryO ARP_tableO[ARP_TABLE_SIZE];
  int line = from_local_arp(ARP_tableO); 

  main_server(ARP_tableO, line); // pocuva tcp, vysle arp

}


void main()
{
  static struct IPlist *IPlist[ARP_TABLE_SIZE];  

  pthread_t thread1, thread2;
  int  iret1, iret2;

  /* Create independent threads each of which will execute function */

  iret1 = pthread_create( &thread1, NULL, lineOne, (void *)IPlist); //(void *) &
  iret2 = pthread_create( &thread2, NULL, lineTwo, NULL); 

  pthread_join( thread1, NULL);
  pthread_join( thread2, NULL);


}

Answer 1

you could handle SIGINT, but it doesn’t matter, your code already corrupts the memory by the time you want to do that extra free() call.

to find the problem compile it with -g and run it with valgrind.