c++ - pthread loop overwriting pointers -

i writing simple barbershop c/c++ project classes, pthreads, mutex, , conds running issue when create new customer object in loop:

void barbershop::simulate() { barber.start(); // start barber int custid = 1; while(1) {     customer c(custid, *this);     customers.push_back(c);     c.start();     sleep(3);     custid++; } 

}

void customer::start() {     pthread_create(&thread, null, &customer::run, this); }  void* customer::run(void *ptr) {     customer* data = reinterpret_cast<customer*>(ptr);     while(1) {         printf("customer %d running...\n", data->id);         sleep(3);     } } 

when run program create threads fine whenever make new thread overwrite id's in other threads. output:

customer 1 running... 1 sec customer 1 running... 2 sec customer 1 running... 3 sec customer 2 running... 4 sec customer 2 running... 4 sec 

in loop say:

customer c(...); 

does not create new instance each loop iteration? why subsequent threads overwrite this?

update

class customer { private:     pthread_t thread;     pthread_cond_t cond;     pthread_mutex_t mutex;     static void* run(void *args);     int id;     barbershop *bs; public:     customer(int _id, barbershop &_bs);     ~customer();     void start(); };   customer::customer(int _id, barbershop &_bs) { id = _id; bs = &_bs; } 

update 2: pthread id's

customer 1 running...[3066383168] customer 2 running...[3057990464] customer 2 running...[3057990464] customer 3 running...[3049597760] customer 3 running...[3049597760] customer 3 running...[3049597760] customer 3 running...[3049597760] customer 4 running...[3049597760] customer 4 running...[3041205056] customer 4 running...[3041205056] customer 4 running...[3041205056] customer 5 running...[3041205056] customer 4 running...[3041205056] customer 5 running...[3032812352] customer 5 running...[3032812352] 

in following segment

while(1) {     customer c(custid, *this);     customers.push_back(c);     c.start();     sleep(3);     custid++; } 

class instance c local scope of while loop. @ end of each iteration of loop, c destroyed.

so, when customers.push_back(c) copy of class taken (see (default) copy constructor) , added customers list. means when c.start() copy pushed onto vector has not been started, instance local loop. @ end of loop iteration of loop c destroyed. loop starts again , new c created.

edit: see martin james' , casey 's comments why behavior you're seeing happening