c pthread passing array of type int

Question

I am passing an array of type int pthread_create and getting error:

  histogram.c:138:3: warning: passing argument 3 of
 ‘pthread_create’ from incompatible   pointer type [enabled by default]
  expected ‘void * (*)(void *)’ but argument is of type ‘void * (*)(int *)’

  void *output_results();
  pthread_create(&t2, NULL, output_results, (void *)bins);

  void *output_results(int *bins) {
      some code
  }

Simon · Accepted Answer · 2013-10-08 17:47:35Z

6

Should be

void *output_results(void*);
pthread_create(&t2, NULL, output_results, (void *)bins);

void *output_results(void *data) {
    int *bins = (int*)data;
    // some code
}

The error message is pretty clear: the function should be of type void * (*)(void *) and not void * (*)(int *) (plus your prototype for output_results was not matching its definition).

answered Oct 8, 2013 at 17:47

Simon

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2 Comments

Jed I Over a year ago

didnt think of that, why didn't the cast work in the pthread_create ?

Simon Over a year ago

You were casting the fourth argument of pthread_create whereas the problem is about the third one: the function pointer. The prototype of pthread_create requires the third argument to be of type void * (*)(void *).

Brian Cain · Accepted Answer · 2013-10-08 17:48:39Z

0

The compilation error is because pthread_create expects void *output_results(void *bins), but you have int *bins.

Also, the declaration of output_results you're using does not match its definition.

answered Oct 8, 2013 at 17:48

Brian Cain

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