Question

I am very new to the linux OS so I am trying to design a shared library witch will start a thread i have the followin code :

1. The function init_log doesn’t raise a segmentation fault it doesn’t display noting in the log though can some one tell me why ?

2. The function pthread_create raises a segmentation fault i use derror() to print that in the log!

---

void __attribute__ ((constructor)) setup();

void init_log()
{
    setlogmask(LOG_UPTO(LOG_NOTICE));
    openlog("TRACKER",LOG_CONS | LOG_PID | LOG_NDELAY, LOG_LOCAL1);
}

    void loop()
    {
        while (0 == 0)
        {
            syslog(LOG_NOTICE,"OK BOSS");
            sleep(1000);
        }
    }

    void setup()
    {
        pthread_t thread_id;
        init_log();
        syslog(LOG_NOTICE,"LIB LOADED"); // this doesn't display
        pthread_create(&thread_id,0,&loop,(void*)(NULL));
    }

COMPILER LINKER PARAMS

**** Build of configuration Debug for project gt_trackers ****

make all 
Building target: libgt_trackers.so
Invoking: GCC C Linker
gcc -shared -o "libgt_trackers.so"  ./main.o   
Finished building target: libgt_trackers.so

**** Build Finished ****

Answer 1

The function void loop() should be void *loop (void *)

and the call the pthread_create should be

pthread_create(&thread_id,0,loop,NULL); 

The prototype for pthread_create is as below. You should match the prototype of your loop function with “start_routine” mentioned below.

int pthread_create(pthread_t *thread, const pthread_attr_t *attr,
                   void *(*start_routine) (void *), void *arg);

The other point is that, just providing the name of a function is sufficient to pass it’s address. No need to add an & before it.

Link to Pthread Tutorial: https://computing.llnl.gov/tutorials/pthreads/

As pointed out by alk, no need to typecast “NULL” also. Thanks alk. : )