pthread & its bug

pthread & its bug

[Mohsen Pahlevanzadeh]

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Dear all,

I'm newbie in multithread programming.I'm practicing that.Now i have
written following code :

My code :

#include <stdio.h>
#include <stdlib.h>
#include <pthread.h>
int g1=0;
int g2=0;
void task1(int *counter);
void task2(int *counter);
int main(int argc,char *argv[])
{
    pthread_t *thr1,*thr2;
    int ret;

    if ((ret = pthread_create(&thr1,NULL,(void *)task1,(void *)&g1)))
    {
        perror("pthread_create : task1");
        exit(EXIT_FAILURE);
    }

    if ((ret = pthread_create(&thr2,NULL,(void *)task2,(void *)&g2)))
    {
        perror("pthread_create : task2");
        exit(EXIT_FAILURE);
    }


    pthread_join(thr2,NULL);
    pthread_join(thr1,NULL);

    cleanup(g1,g2);
    exit(EXIT_SUCCESS);
}//end of main program
void task1(int *counter)
{
    while(*counter < 5 ){
        printf("task1 count: %d\n",*counter);
        (*counter)++;
    }//end of while
}//end of task1 function

void task2(int *counter)
{
    while(*counter < 5 ){
        printf("task2 count: %d\n",*counter);
        (*counter)++;
    }//end of while
}//end of task1 function
void cleanup(int counter1,int counter2)
{
    printf("Total iterations: %d\n",counter1+counter2);
}//end of cleanup function
///////////////////////////END OF
CODE////////////////////////////////////////////////////////

Now when i compile it, I receive following errors:

mohsen@debian:~/test/learning/pthread$ make
gcc -c  test.c
In file included from test.c:3:
/usr/include/pthread.h:285: error: conflicting types for ‘pthread_t’
/usr/include/bits/pthreadtypes.h:152: error: previous declaration of
‘pthread_t’ was here
/usr/include/pthread.h:286: error: conflicting types for ‘pthread_attr_t’
/usr/include/bits/pthreadtypes.h:54: error: previous declaration of
‘pthread_attr_t’ was here
/usr/include/pthread.h:287: error: conflicting types for ‘pthread_key_t’
/usr/include/bits/pthreadtypes.h:82: error: previous declaration of
‘pthread_key_t’ was here
/usr/include/pthread.h:289: error: conflicting types for
‘pthread_mutexattr_t’
/usr/include/bits/pthreadtypes.h:102: error: previous declaration of
‘pthread_mutexattr_t’ was here
/usr/include/pthread.h:290: error: conflicting types for ‘pthread_mutex_t’
/usr/include/bits/pthreadtypes.h:95: error: previous declaration of
‘pthread_mutex_t’ was here
/usr/include/pthread.h:291: error: conflicting types for
‘pthread_condattr_t’
/usr/include/bits/pthreadtypes.h:79: error: previous declaration of
‘pthread_condattr_t’ was here
/usr/include/pthread.h:292: error: conflicting types for ‘pthread_cond_t’
/usr/include/bits/pthreadtypes.h:72: error: previous declaration of
‘pthread_cond_t’ was here
test.c: In function ‘main’:
test.c:13: warning: passing argument 1 of ‘pthread_create’ from
incompatible pointer type
test.c:19: warning: passing argument 1 of ‘pthread_create’ from
incompatible pointer type
test.c:26: warning: passing argument 1 of ‘pthread_join’ from
incompatible pointer type
test.c:27: warning: passing argument 1 of ‘pthread_join’ from
incompatible pointer type
test.c: At top level:
test.c:48: warning: conflicting types for ‘cleanup’
test.c:29: warning: previous implicit declaration of ‘cleanup’ was here
make: *** [main.o] Error 1
mohsen@debian:~/test/learning/pthread$

//////////////////////////////////////


I have retrieved libdir & includedir with pthread_config command.

Please help me .....

Yours,Mohsen
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RE: pthread & its bug

[John (Eljay) Love-Jensen]

Hi Mohsen,

Your inquiry is off topic for this forum.  I do not say this to chastize you.  I say it because you may get better / faster / more accurate information from a more appropriate forum that is pthread savvy.

There are a whole bunch of errors in your test source code.

For example, the pthread_create's third parameter takes a function pointer to a function that looks like:

void* task(void* ptr);

You are passing in a function pointer to a function that looks like:

void task(int* counter);

And you are casting the function pointer to a data pointer:

(void*)task1

That doesn't fit.

Another example, pthread_create's first parameter takes a pointer to a pthread_t.  You are passing in a poiter to a pointer to a pthread_t.  (And that pointer-to-a-pointer has not been allocated anywhere.)

That doesn't fit.

Work through all the mismatched data types, and then see where things end up.  GCC helps you, by emitting a lot of warnings and errors.  Heed them.

Don't forget to:

gcc test.c -lpthread

HTH,
--Eljay

Re: pthread & its bug

[bjorn rohde jensen]

John (Eljay) Love-Jensen wrote:
> Hi Mohsen,
> 
> Your inquiry is off topic for this forum.  I do not say this to chastize you.  I say it because you may get better / faster / more accurate information from a more appropriate forum that is pthread savvy.
> 
> There are a whole bunch of errors in your test source code.
> 
> For example, the pthread_create's third parameter takes a function pointer to a function that looks like:
> 
> void* task(void* ptr);
> 
> You are passing in a function pointer to a function that looks like:
> 
> void task(int* counter);
> 
> And you are casting the function pointer to a data pointer:
> 
> (void*)task1
> 
> That doesn't fit.
> 
> Another example, pthread_create's first parameter takes a pointer to a pthread_t.  You are passing in a poiter to a pointer to a pthread_t.  (And that pointer-to-a-pointer has not been allocated anywhere.)
> 
> That doesn't fit.
> 
> Work through all the mismatched data types, and then see where things end up.  GCC helps you, by emitting a lot of warnings and errors.  Heed them.
> 
> Don't forget to:
> 
> gcc test.c -lpthread
> 
> HTH,
> --Eljay

You might want to define your task functions to have the type expected
by phtread_create instead of casting them, something like;

void *task1(void *p)
{
  int *counter=(int *)p;

    while(*counter < 5 ){
        printf("task1 count: %d\n",*counter);
        (*counter)++;
    }

    return NULL;
}

The type system is there to help you, dont cast things unless you really
need to.