Spiral rule and 'declaration follows usage' for parsing C expressions

Question

This question follows this other question about C declaration. Reading the answer to this question, I read about the spiral rule and I also understood what "declaration follows usage" means.

Ok so far. But then I read this declaration:

char *(*(*a[N])())(); 

and I was wondering how to parse it with the "declaration follows usage" 'rule'. Especially for the array part.

What I read is:

(*(*a[N])()) 

is a function () returning a char *, then, dereferencing the following

(*a[N])() // 1

is this 'function returning a char*', and so 1 is a 'pointer to a function returning char *' then I would say 'when (*a[N]) is called, it is [previous declaration]'. At this point we have (*a[N]) is a function returning a pointer to a function returning char *.

But then I don't know how to apply this rule to distinguish between the 'pointer to array' and 'array of pointer'.

Can someone clarify this ?

Other question: what are the rule of "precedence" in such declarations, between & (in C++), *, and [] ? [maybe "precedence" is not the correct term]

---

To check if I understood the 'spiral rule' correctly, I also parse this expression bellow, tell me if I am wrong.

       +-----------+
       | +------+  |
       | | +-+  |  |
       | | ^ |  |  |
char* (*(* a[N])())(); 
    ^  ^ ^   ^  ^  ^
    |  | |   |  |  |
    |  | +---+  |  |
    |  +--------+  |
    +--------------+

For me it is easier (loop by loop):

• a is an array of N ...
• pointer to function returning ...
• pointer to function returning ...
• char *

But I am maybe missing something which in that case let me obtain the correct answer but that could be wrong in another more complicated case.

Answer 1

You just have to build it up in steps.

char *X();  // X =~ (*(*a[N])())

Function returning char*

char *(*Y())();  // Y =~ (*a[N])

Function returning pointer to function returning char*.

In a declaration, just as in an expression (declaration follow usage), postfix [] has a higher precedence that unary * so *a[N] is equivalent to *(a[N]), not (*a)[N].

char *(*(*Z)())();  // Z =~ a[N]

Pointer to function returning pointer to function returning char*.

char *(*(*a[N])())();

Array of N pointers to functions returning a pointer to function returning char*.