gcc warning line number mismatch

[neelabhg]

When compiling the following program (from https://computing.llnl.gov/tutorials/pthreads/samples/hello.c):

/******************************************************************************
* 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);
}

gcc outputs this:

program.c: In function 'main':
program.c:43:15: warning: unused parameter 'argc' [-Wunused-parameter]
  int main(int argc, char *argv[])
               ^
program.c:43:27: warning: unused parameter 'argv' [-Wunused-parameter]
  int main(int argc, char *argv[])
                           ^

The last line of the program is line 38, but the warning appears on line 43.

Why? Even if this has to do with gcc, it still affects our user experience, and so I thought this needed to be brought to attention.

[wchill]

First I thought this was likely editor related. When I copy paste the above example into the editor, it gets transformed into this:

/******************************************************************************
 * * 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);
 }

Note the extra asterisks in the comments and the space at the beginning of each line.

I did try disabling "Autoindent code" in the editor options - it fixes the above issue but doesn't fix the issue with the compiler output.

However, if you open program.c in the VM, there's an extra blank line in between every line. And if you watch the code get transmitted to the VM during compilation, those blank lines are there also. So likely we need to inspect the module that handles this.

[neelabhg]

Great catch. BTW, I opened issue #99 earlier for the comment block + auto indentation problem you mentioned.

[wchill]

If you compile the program without that comment block, it actually seems to work fine

#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);
}

program.c: In function 'main':
program.c:27:14: warning: unused parameter 'argc' [-Wunused-parameter]
  int main(int argc, char *argv[])
               ^
program.c:27:26: warning: unused parameter 'argv' [-Wunused-parameter]
  int main(int argc, char *argv[])
                           ^