threadDeath2.cc

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#include <iostream>
#include <string>
#include <pthread.h>

using namespace std;

void *myfunc(void *arg);

struct func_params
{
  void *(*user_func)(void *);
  void *argument;
  void *other_info;
};

void *func(void *arg)
{
  //grab the parameters for redability (demonstration purposes)
  struct func_params *params = (struct func_params *)arg;

  //print out other info from the paramater structure
  cout << (char *)params->other_info << endl;

  //call the user function with the intended argument (void *)
  void *return_value = params->user_func(params->argument);

  //exit thread
  pthread_exit(return_value);

  return NULL;
}

int main(int argc, char *argv[])
{
  //track the thread ID
  pthread_t tid;

  //capture the return value of our user defined function (ultimately
  //from a call from pthread_exit in our wrapper function).
  void **ret;

  //create a string to pass to our user defined function
  string arg("string from main");
  
  //create a func_params object to pass to our wrapper function
  struct func_params params;

  //set the members of the func_params object
  params.user_func = myfunc;    // pointer to user defined function
  params.argument = &arg;       // object passed to user function

  //more data -for demonstration 
  params.other_info = (void *)"literal string in main params"; 

  //create the thread (passing our wrapper function as the function
  //argument)
  pthread_create(&tid, (pthread_attr_t *)NULL, func, (void *)&params);

  //join the thread -simple enough
  pthread_join(tid, ret);

  //check the return value 
  if(*ret != NULL)
    {
      //if the contents of the pointer to a pointer (ret) is not NULL...

      //print the contents -casting it as what we expect it to be
      cout << *((string *)(string *)*ret) << endl;

      //delete the pointer because we don't want memory leaks
      delete ((string *)(string *)*ret);
    }

  //arg falls out of scope and is handled by the string destructor
  //after return.

  //exit normally
  return(0);
}

void *myfunc(void *arg)
{
  //print out the argument passed in
  cout << *(string *)arg << endl;
  
  //allocate for a new string object
  string *s = new string("string from myfunc");

  //display our string: for demonstration
  cout << "myfunc returning:" << *s <<endl;

  //pthread_exit((void *)s);    // BAD, BAD, BAD

  //return the object as a void pointer
  return( (void *)s);
}