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Bacardi34

Cant get get pthreading working

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Hi, im trying to learn about using threads and i made a simple program like one in a tutorial i am reading through. problem is that i cant get it to compile. here is my program.
[source=cpp]
#include <stdio.h>
#include <pthread.h>

void * work( )
{
  int i;
  for( i = 0; i < 11; i++ )
    {
      fprintf( stdout, "%d\n", i );
      usleep( 1000 );
    }

  pthread_exit(0);
  return;
}


int main()
{
  pthread_t t1, t2;

  pthread_create(&t1, 0, work, (void *)0);
  pthread_create(&t2, 0, work, (void *)0);

  pthread_join(t1, 0);
  pthread_join(t2, 0);

  return 0;
}

and here is my makefile multithread.o: multithread.c gcc ${OPT} -c multithread.c multithread: multithread.o gcc ${OPT} -o multithread multithread.o when i go make multithread i get errors saying: gcc -O3 -g -o multithread multithread.o multithread.o(.text+0x17): In function `main': /home/brain/testproj/multithread.c:26: undefined reference to `pthread_create' multithread.o(.text+0x29):/home/brain/testproj/multithread.c:27: undefined reference to `pthread_create' multithread.o(.text+0x36):/home/brain/testproj/multithread.c:29: undefined reference to `pthread_join' multithread.o(.text+0x42):/home/brain/testproj/multithread.c:30: undefined reference to `pthread_join' Any idea why it cant link correctly? i tried doing -l /usr/lib/libpthread.a but that had no effect. Thanks for the help!

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I beleieve it should just be

gcc -O3 -g -lpthread multithread.o -o multithread

Of course a lot of it depends on how your compiler is set up but in the general case that is how it works. The -l flag automatically adds lib to the front and .a to the end.
So if you did -l/usr/lib/libpthread.a it will become lib/usr/lib/libpthread.a.a

If you want to specify a library directory you use the -L option like
-L/usr/lib -lpthread

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