How to fix invalid conversion error while using pthread_create()?

[bajajv]

Hi,
My code is -

void func1(void* arg)
{
  printf("In child thread.\n");
}
 
int main()
{
  int ret;
  pthread_t tid; 
  void (*start_routine) (void*);
  start_routine = &func1;
  ret = pthread_create(&tid, NULL, start_routine, attr);
  printf("In main thread.\n");
  return 0;
}
 

I am getting the error - Invalid conversion from
void (*) (void*) to void* (*) (void*)
I did not understand why this extra * is coming into picture?

[horace1]

I think the function should be

void* func1(void* arg)
{
  printf("In child thread.\n");
}
 

and 10 should be

  void *start_routine (void*);
 

[bajajv]

well no, it is not working.

if we change line 10, will start_routine be still a function pointer, because it doesn't have that * now inside the braces?

[horace1]

you are correct, looking again line 10 should be

  void *(*start_routine) (void*);
 

[bajajv]

I did not understood one thing.. why do i need to make my func1 returning void* and the function pointer type as void* (*start_routine) (void*)?

[horace1]

if you look at the specification
http://pubs.opengroup.org/onlinepubs...ad_create.html

of pthread_create

int pthread_create(pthread_t *thread, const pthread_attr_t *attr,
    void *(*start_routine)(void*), void *arg);
 

the third parameter is a pointer to a function which takes a single parameter pointer to void and returns a pointer to void as a function result. Hence start_routine must be

void* func1(void* arg)
 

[bajajv]

hmm.. I should have checked that first..
thanks for the help...