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Passing a parameter to a thread

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• Passing a parameter to a thread
  • The function executed by a thread can have one parameter

    Multiple parameters:

    Multiple parameters can be passed by passing the address of a data structure as the parameter

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  • To accomodate different types of parameter, the casting (type conversion) operation is usually needed

  • Example: passing an integer parameter to a thread

    /* -------------------------------------------------------- Worker thread will receive an INTEGER input parameter -------------------------------------------------------- */ void *worker(void *arg) { int *p; // Pointer (reference, address) to an integer variable int x; // An integer variable p = (int *) arg; // Casting "(void *)" type to "(int *)" x = *p cout << "Hi, my input parameter is " << x << endl; return(NULL); /* Thread exits (dies) */ }

    /* -------------------------------------------------------- Main creates thread and passes param to new thread -------------------------------------------------------- */ int main(int argc, char *argv[]) { pthread_t tid; int param; // Integer param = 12345; pthread_create(&tid[i], &attr, worker, & param); pthread_join(tid, NULL); // Wait for the thread to end... }

    • Example Program: (Pass parameter to thread) --- click here        
      • Compile with: g++ -pthread param.C

    Try changing the type from int to float Only in main Only in worker In both main and worker You will see that they must agree !