Spiral rule and 'declaration follows usage' for parsing C and C++ declarations

问题

This question follows this other question about C declarations. 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 rules 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 below; please 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.

回答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*.

来源：https://stackoverflow.com/questions/3707096/spiral-rule-and-declaration-follows-usage-for-parsing-c-and-c-declarations