Solved

C++ multithreading code does not compile

Posted on 2013-01-16
4
409 Views
Last Modified: 2013-01-16
Hello experts!

I am using ubuntu and geanie.
I try to compile following code:


/******************************************************************************
* FILE: hello.c
* DESCRIPTION:
*   A "hello world" Pthreads program.  Demonstrates thread creation and
*   termination.
* AUTHOR: Blaise Barney
* LAST REVISED: 08/09/11
******************************************************************************/
#include <pthread.h>
#include <stdio.h>
#include <stdlib.h>
#define NUM_THREADS      5

void *PrintHello(void *threadid)
{
   long tid;
   tid = (long)threadid;
   printf("Hello World! It's me, thread #%ld!\n", tid);
   pthread_exit(NULL);
}

int main(int argc, char *argv[])
{
   pthread_t threads[NUM_THREADS];
   int rc;
   long t;
   for(t=0;t<NUM_THREADS;t++){
     printf("In main: creating thread %ld\n", t);
     rc = pthread_create(&threads[t], NULL, PrintHello, (void *)t);
     if (rc){
       printf("ERROR; return code from pthread_create() is %d\n", rc);
       exit(-1);
       }
     }

   /* Last thing that main() should do */
   pthread_exit(NULL);
}


I get error messages:


g++ -Wall -o "main" "main.cxx" (in directory: /home/jacek/Documents/cpp/wlasne/MultiThreading/4)
/tmp/ccvE3G41.o: In function `main':
main.cxx:(.text+0x85): undefined reference to `pthread_create'
collect2: ld returned 1 exit status
Compilation failed.

What do I do wrong?

Thank you

panJames
0
Comment
Question by:panJames
  • 2
  • 2
4 Comments
 
LVL 31

Accepted Solution

by:
Zoppo earned 500 total points
ID: 38783034
Hi panJames,

I guess you need to link 'pthread' library into your program. Try adding -lpthread to the command line ...

Hope that helps,

ZOPPO
0
 

Author Comment

by:panJames
ID: 38783126
g++ -Wall -o -lpthread "main" "main.cxx" (in directory: /home/jacek/Documents/cpp/wlasne/MultiThreading/4)
g++: error: main: No such file or directory
Compilation failed.
0
 

Author Comment

by:panJames
ID: 38783131
g++ -Wall -o -lpthread "%e" "%f"
0
 
LVL 31

Expert Comment

by:Zoppo
ID: 38783141
Hi,

you should not add this directly after -o. The argument after -o is the name of the resulting executable.

ZOPPO
0

Featured Post

Efficient way to get backups off site to Azure

This user guide provides instructions on how to deploy and configure both a StoneFly Scale Out NAS Enterprise Cloud Drive virtual machine and Veeam Cloud Connect in the Microsoft Azure Cloud.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Little introduction about CP: CP is a command on linux that use to copy files and folder from one location to another location. Example usage of CP as follow: cp /myfoder /pathto/destination/folder/ cp abc.tar.gz /pathto/destination/folder/ab…
Linux users are sometimes dumbfounded by the severe lack of documentation on a topic. Sometimes, the documentation is copious, but other times, you end up with some obscure "it varies depending on your distribution" over and over when searching for …
Learn how to navigate the file tree with the shell. Use pwd to print the current working directory: Use ls to list a directory's contents: Use cd to change to a new directory: Use wildcards instead of typing out long directory names: Use ../ to move…
The viewer will learn how to use the return statement in functions in C++. The video will also teach the user how to pass data to a function and have the function return data back for further processing.

810 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question