Confusing clone passing down argument - c++

Question

So basically I am solving the famous "Philosopher dining" problem, 5 philosopher is generating out using clone. The point is I want each philosopher to hold a id (from 0 to 4). I plan to do it using clone passing down argument. Here is the code (I omit some sub function)
void philoshopher(void* arg)
{
int i = &arg;
while (TRUE)
{
printf("Philosopher %d is thinking", i);
take_forks(i);
printf("Philosopher %d is eating", i);
sleep(2);
put_forks(i);
}
}
int main(int argc, char **argv)
{
int i;
int a[N] = {0,1,2,3,4};
void* arg;
/*
struct clone_args args[N];
void* arg = (void*)args;
*/
if (sem_init(&mutex, 1, 1) < 0)
{
perror(NULL);
return 1;
}
for (i=0;i<N;i++)
{ if (sem_init(&p[i], 1, 1) < 0)
{
perror(NULL);
return 1;
}
}
int (*philosopher[N])() ;
void * stack;
for (i=0; i<N; i++)
{
if ((stack = malloc(STACKSIZE)) == NULL)
{
printf("Memorry allocation error");
return 1;
}
int c = clone(philosopher, stack+STACKSIZE-1, CLONE_VM|SIGCHLD, &a[i]);
if (c<0)
{
perror(NULL);
return 1;
}
}
//Wait for all children to terminate
for (i=0; i<4; i++)
{
wait(NULL);
}
return 0;
}
After compile out, I get this error:
passing argument 1 of ‘clone’ from incompatible pointer type [enabled by default]
expected ‘int (*)(void *)’ but argument is of type ‘int (**)()’
I also try to cast this to a void pointer but still same result:
void* arg;
....
arg = (void*)(a[i]);
int c = clone(...., arg);
Anyone know how to fix this. Thanks for your help.

Answer 1

You aren't declaring your function pointer correctly. It should look like this:
int (*philosopher[N])(void*);
Basically when you're declaring function pointers you have to specify the argument type, because pointers to functions that accept different types are (thankfully!) incompatible with each other.
I think you also need to remove the & before a[i] in the function call. That's giving you a pointer to a function pointer, and it just expects a plain function pointer apparently.