Complex declarations

Question

How do I interpret complex declarations like:

int * (* (*fp1) (int) ) [10]; ---> declaration 1
int *( *( *[5])())(); --------> declaration 2
         


        

Answer 1

Start with the leftmost identifier and work your way out, remembering that absent any explicit grouping [] and () bind before *, e.g:

    *a[]                 -- is an array of pointer
  (*a)[]                 -- is a pointer to an array
    *f()                 -- is a function returning pointer
  (*f)()                 -- is a pointer to a function

Thus, we read int *(*(*fp1)(int))[10] as:

         fp1                     -- fp1
        *fp1                     -- is a pointer
       (*fp1)(int)               -- to a function
                                      taking an int parameter
      *(*fp1)(int)               -- returning a pointer
     (*(*fp1)(int))[10]          -- to a 10-element array
    *(*(*fp1)(int))[10]          -- of pointer 
int *(*(*fp1)(int))[10]          -- to int

The declaration int *(*(*[5])())() presents a bit of a challenge since there's no identifier; you typically see this in function declarations where a parameter is of that type:

void foo(int *(*(*[5])())(), double);

It's the same principle as the unnamed int parameter in the declaration of fp1. The array gives us the clue, you can also look for the leftmost inner grouping of parentheses.

                         -- unnamed
         [5]             -- is a 5-element array ([] binds before *)
        *[5]             -- of pointers
       (*[5])()          -- to functions
      *(*[5])()          -- returning pointers
     (*(*[5])())()       -- to functions
    *(*(*[5])())()       -- returning pointers
int *(*(*[5])())()       -- to int