Error in passing an element of vector of structures to pthread_create()

Question

I have to create a vector of structures and pass a structure element as the first argument of pthread_create() function.

The code snippet is as follows:

struct example
{
int myint;
pthread_t thread;
};

int main()
{
.............
vector<example> obj;
int count = 1;
while(count < n)
{
int *thread_id = new int(count);                  
pthread_create(&(obj[count].thread), NULL, worker_routine, thread_id);
count = count+1;
........................
.........................
    }
}

I have only included the parts of code that I think has triggered the following error:

Program received signal SIGSEGV, Segmentation fault.
0x00007ffff7629e4f in __pthread_create_2_1 (newthread=<optimized out>, attr=<optimized out>, 
start_routine=<optimized out>, arg=<optimized out>) at pthread_create.c:631
631 pthread_create.c: No such file or directory.

Answer 1

Your problem is with vector. Because in the vector you did not add any element and you are trying to access like below.

obj[count].thread //obj does not have any element

Make changes like below:-

struct example e1, e2, e3,e4,e5;
obj.push_back(e1);
obj.push_back(e2);
obj.push_back(e3);
obj.push_back(e4);
obj.push_back(e5);

while(count < 5)
{
     int *thread_id = new int(count);                  
     pthread_create(&(obj[count].thread), NULL, worker_routine, thread_id);
     struct example e;
     obj.push_back(e);

One more option:- struct example e1; vector obj(e1); int count = 1; while(count < n) { int *thread_id = new int(count);
pthread_create(&(obj[count].thread), NULL, worker_routine, thread_id);

Better use C++ style of multi threading it is much easier:-

struct example
{
   int myint;

  void operator()()
  {
      std::cout<<"I am thread :"<<myint<<std::endl;     
  }       
};

int main()
{
   struct example exmp;
   exmp.myint = 1;
   std::thread t1(exmp);
   t1.join();
   return 0;
}