CODEWITHSUNDEEP
cgcccompilationlinkerpthreads
Dago
Dago

Reputation: 808

No input files or undefined reference when compiling C on Ubuntu

i am trying to compile this code in C. I am using

 gcc -o -pthread test1.c

I am using Linux. Unfortunately I get:

undefined reference to `pthread_create'
 undefined reference to `thread_join'
  collect2: error: ld returned 1 exit status

When I try to compile:

    #include <stdio.h>
    #include <pthread.h>
    #include <stdlib.h>


    void* thread_func(void* parameter){

        int i =0;
        for(i=0; i<5;i++)
        {
            printf("%d\n", i);
        }

      return 0;


    }


 int main (int argc, char *argv)
 {
     pthread_t thread_handle;
     int ret = pthread_create(&thread_handle,0,thread_func,0);
     if(ret != 0) {
        printf("Create thread failed! error: %d",ret);
        return 1;
      }

      thread_join(thread_handle,0);

      return 0;

}

When I use the second solution from here: Undefined reference to pthread_create in Linux

I get another error. I am in the directory where my test1.c .

no input files





ADDIN ERRORS:
1)using gcc -o someFile -pthread test1.c
-undefined reference to `thread_join'
2)gcc -o -pthread test1.c
-undefined reference to `thread_join'
-undefined reference to `pthread_create'

3)gcc test1.c -o test1.o -I. -lpthread 
- undefined reference to `thread_join'
4)gcc -pthread -o test.c
- no input files

I would be grateful for help because I can't learn threads because I can't compile it.

Upvotes: 0

Views: 989

Answers (3)

geert3
geert3

Reputation: 7321

Word after option -o is the output file, i.e. you specified -pthread to be the output file. Change to gcc -o someFile -pthread test1.c should do the trick. Your executable output file would then be someFile.

Upvotes: 1

user3629249
user3629249

Reputation: 16540

The linker takes things in the order written on the command line.

So, in your example, when the linker gets to your .o file, and needs to find the external reference for the pthread calls, it has nothing to look in.

You could try:

gcc test1.c -o test1.o -I. -lpthread

The -I. says to look for #include "header.h" files in the current directory the -lpthread says to use the libpthread.a library file.

Upvotes: 0

antonpuz
antonpuz

Reputation: 3316

try compiling with -lpthread

gcc -lpthread test1.c -o test1

Upvotes: 0

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