Thread: Pointers vs. Pointers to pointers

I keep seeing code that uses the the same function twice, but one copy of the function will use pointers to an array, and another will use pointers to pointers to an array.

Is there a difference in execution between these two methods, or is it just preference?

Please show some examples to illustrate your question.

Jim

Code:

      int compA(const void* item1, const void* item2) {
      const Emp* emp1 = (const Emp*) item1;
      const Emp* emp2 = (const Emp*) item2;
      
      unsigned char buff1[BuffSize + 1];
      unsigned char buff2[BuffSize + 1];
    
      strcpy(buff1, emp1->lname);
      strcat(buff1, emp1->fname);
      strcpy(buff2, emp2->lname);
      strcat(buff2, emp2->fname);
   
      return strcmp(buff1, buff2);
    }

and

Code:

    int compB(const void* item1, const void* item2) {
      const Emp** emp1 = (const Emp**) item1;
      const Emp** emp2 = (const Emp**) item2;
    
   unsigned char buff1[BuffSize + 1];
   unsigned char buff2[BuffSize + 1];
   
      strcpy(buff1, (*emp1)->lname);
      strcat(buff1, (*emp1)->fname);
      strcpy(buff2, (*emp2)->lname);
      strcat(buff2, (*emp2)->fname);
    
      return strcmp(buff1, buff2);
   }

Or

Code:

 void dump_emps1(Emp a[ ], unsigned n) {
   102   int i;
        char buffer[BuffSize + 1];
        for (i = 0; i < n; i++) {
        to_string(&a[i], buffer);
        printf("%s\n", buffer);
      }  
    }

and

Code:

       void dump_emps2(Emp* a[ ], unsigned n) {
       int i;
       char buffer[BuffSize + 1];
       for (i = 0; i < n; i++) {
       to_string(a[i], buffer);
       printf("%s\n", buffer);
      }
   }

Eww.

>> Do you not feel "Eww" about the original code duplication?
>> How was that not the ideal solution, care to elaborate?

I'd rather just decide on one way to allocate Emp structures, to be honest. Other than that, nothing is wrong.