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I have recently installed XUbuntu 11.10 64bit, but I am having problem compiling the most simple pthread example.

Here is the code pthread_simple.c:

#include <stdio.h>
#include <pthread.h> 
main()  {
  pthread_t f2_thread, f1_thread; 
  void *f2(), *f1();
  int i1,i2;
  i1 = 1;
  i2 = 2;
void *f1(int *x){
  int i;
  i = *x;
  printf("f1: %d",i);
void *f2(int *x){
  int i;
  i = *x;
  printf("f2: %d",i);

And here is the compile command

gcc -lpthread pthread_simple.c

The results:

lptang@tlp-linux:~/test/test-pthread$ gcc -lpthread pthread_simple.c 
/tmp/ccmV0LdM.o: In function `main':
pthread_simple.c:(.text+0x2c): undefined reference to `pthread_create'
pthread_simple.c:(.text+0x46): undefined reference to `pthread_create'
pthread_simple.c:(.text+0x57): undefined reference to `pthread_join'
pthread_simple.c:(.text+0x68): undefined reference to `pthread_join'
collect2: ld returned 1 exit status

Does anyone know what's causing the problem?

share|improve this question
Is it stackexchange's fault that you have empty includes in the first two lines? There should be an #include <pthread.h> – Frg Mar 4 '12 at 13:24
Yes, I used the pre environment. It should now display correctly. – chtlp Mar 4 '12 at 13:27
Tried gcc -pthread...? – sr_ Mar 4 '12 at 13:42
BTW, please compile with -Wall, you're missing headers. (And sr_ is correct.) – Mat Mar 4 '12 at 13:43
Thanks. I changed -lpthread to -pthread and it worked. – chtlp Mar 4 '12 at 13:51

3 Answers 3

up vote 12 down vote accepted

In the latest versions of gcc compiler require that libraries follow the object or source files.

So to compile this it should be:

gcc pthread_sample.c -lpthread

Normally though pthread code is compiled this way:

gcc -pthread pthread_sample.c
share|improve this answer
Thanks, it does the trick! – chtlp Mar 4 '12 at 13:49

compile code using following command

gcc filename.c -lpthread -lrt
share|improve this answer
Hi! It would be helpful if you could edit your answer to explain why it works, and to highlight why you think it adds something the already accepted answer doesn't cover. – dhag Apr 8 at 4:28
gcc -o exectable_namme pthread_sample.c -lpthread
share|improve this answer
It would be helpful to edit your answer to explain why this is different from the already accepted answer. – roaima Nov 20 at 11:17

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