Array of pointers (to structs)

Question

I'm trying to do something like this

typedef struct _thingy_t
{
    int num;
} thingy_t;

void go(int idk)
{
    // normally I could just do
    thingy_t* ary[idk];
    // but I need the array to be global    
}

I need an array of pointers to structs of size idk

Is using a 'double pointer' declared outside of the function the best way to go about this? And what about malloc'ing space for the structs?

Answer 1

You can declare as global and then allocate memory inside function.

if you want to allocate memory for array.

void go(int);  

thingy_t *data=NULL; 
main()
{

   //read idk value.
   go(idk);

}
void go(int idk)
{
        data = malloc(idk * sizeof(thingy_t) );
       // when you allocate memory with the help of malloc , That will have scope even after finishing the function.

}   

---

if you want to allocate memory for array of pointers.

thingy_t **data=NULL;

int main()
{
    int i,idk=10;
    go(idk);

    for(i=0;i<10;i++)
       {
       data[i]->num=i;
       printf("%d ",data[i]->num );
       }

return 0;
}

void go(int idk)
{
   int i=0;
   data=malloc(idk *sizeof( thingy_t * ));
   for ( i = 0; i<idk ; i++) {
      data[i]=malloc(sizeof( thingy_t));
   }
}  

---

Don't forgot to free() the memory which is allocated with malloc.