naming threads, using typedef/struct - c++

Question

I am creating a program to practice using threads. I am trying to name them so that when the program is run, you can clearly see "Flight 1 is taking off..." or "Flight 6 is landing..." and so on. I would like every thread to have a flyTime (so I know what order they will use the runway in) which will be randomly generated. I have tried and am having difficulty using struct/typedef to give each pthread these characteristics so i can say for example flight.flyTime and use it throughout the program. Here is the relevant part of my code without my landing/takeoff functions:
#include <pthread.h>
#include <stdio.h>
#include <cstdlib>
#include <iostream>
#include <queue>
#define NUM_THREADS 8 //8 flights
pthread_mutex_t runway1lock;
void *FlightID(void *flightid){
long fid;
fid = (long)flightid;
pthread_exit(NULL);
}
typedef struct{ //each plane has these characteristics
long fid;
int StartState; // if start=1 ==> taking off:::if start=2 ==> landing
int flyTime; //fly == randomly generated time (order)
}FLIGHTS;
FLIGHTS flights[NUM_THREADS];
int StartState(flights[NUM_THREADS]){
int startState;
for (int i=0; i<=NUM_THREADS; i++){
startState = rand() % 1+2;
}
std::string start;
if(startState == 1){
start = "Taking off";
}
if(startState == 2){
start = "Landing";
}
for (int t=0; t<NUM_THREADS; t++){
std::cout << "Start State for Flight# " << FlightID << " is " << start << std::endl;
}
return startState;
}
int main(int argc, char *argv[]){
// pthread_t flights[NUM_THREADS]; //pthread_t keeps a thread ID after the thread is created with pthread_create()
//it's like an index on a vector of threads
int rc;
long t;
for (t=1; t<=NUM_THREADS; t++){ //loop creates threads(flights)
printf("In main: Creating flight %1d\n", t);
rc = pthread_create(&flights[t], NULL, FlightID, (void *)t);
if (rc){
printf("ERROR: return code from pthread_create() is %d\n", rc);
return (-1);
}
printf("Created flight %1d\n", t);
StartState(flights[t]); //gives every flight a start state
if(StartState(flights[t])==1){
std::cout << "Flight # " << &flights[t] << " is listed as waiting at the gate." << std::endl;
//go to takeoff function and go through switch case
}
if(StartState(flights[t])==2){`enter code here`
std::cout << "Flight # " << &flights[t] << " is listed as waiting to land." << std::endl;
//go to landing function and go through switch case
}
}
pthread_exit(NULL);
}

Answer 1

There is a code snippet below that represents how I would implement it.
You should also take a look at pthread_key_create, pthread_getspecific and pthread_setspecific. This is a set of functions that allow you to have data, specific to each thread, stored in the thread's memory context. It may come in handy for in your code, later on.
typedef struct{
long fid;
int StartState;
int flyTime;
} FLIGHTS;
FLIGHTS** flights = new FLIGHTS*[NUM_THREADS];
pthread_key_t pkey:
void *FlightID(void *flightid){
long fid;
fid = (long)flightid;
FLIGHTS* flight = new FLIGHTS();
flight->fid = fid;
flights[fid] = flight;
pthread_setspecific(pkey, flight);
int startState;
for (int i=0; i<=NUM_THREADS; i++){
startState = rand() % 1+2;
}
std::string start;
if(startState == 1){
start = "Taking off";
}
if(startState == 2){
start = "Landing";
}
for (int t=0; t<NUM_THREADS; t++){
std::cout << "Start State for Flight# " << fid << " is " << start << std::endl;
}
flight->StartState = startState;
}
int main(int argc, char* argv[]) {
pthread_key_create(&pkey, NULL);
for (t=1; t<=NUM_THREADS; t++){
rc = pthread_create(&flights[t], NULL, FlightID, (void *)t);
if (rc){
printf("ERROR: return code from pthread_create() is %d\n", rc);
return (-1);
}
printf("Created flight %1d\n", t);
}
}
Also, I don't know if I'm understanding your code correctly or if you just have some coding errors on it, so I leave you with some questions or remarks that could be mistakes/bugs:
1) You invoke pthread_exit in the start callback function:
void *FlightID(void *flightid){
long fid;
fid = (long)flightid;
pthread_exit(NULL);
}
2) You pass to the << operator a function with no return value:
std::cout << "Start State for Flight# " << FlightID << " is " << start << std::endl;
3) You invoke the same function 3 times just to get the return value. Shouldn't it be int state = StartState(flights[i]) and then test the state variable value?
StartState(flights[t]); //gives every flight a start state
if(StartState(flights[t])==1){
std::cout << "Flight # " << &flights[t] << " is listed as waiting at the gate." << std::endl;
//go to takeoff function and go through switch case
}
if(StartState(flights[t])==2){`enter code here`
std::cout << "Flight # " << &flights[t] << " is listed as waiting to land." << std::endl;
//go to landing function and go through switch case
}
4) You can't define a function like this:
int StartState(flights[NUM_THREADS]){