A pointer to an in-depth parse function pointer and return function

The following is a detailed analysis of the function pointer and the return function of the pointer, the need for friends can come to refer to the next

Let's take a look at the following two codes:
1: Originating from Stl-sgi source <stl_alloc.h>

Copy Code code as follows:


static void (*__set_malloc_handler (*__f) ()) ()


{


void (*__old) () =__malloc_alloc_oom_handler;


__malloc_alloc_oom_handler=__f;


return (__old);


}

<sginal.h> under the 2:linux

Copy Code code as follows:


void (*signal (int sig_num, void (*handler) (int)) (int)

As a C + + master may be a look at it, the following to analyze, the analysis of the method used is from the inside out of the analytical method

For example 1 analysis is as follows:
1 The innermost is void (*_f) () The _f is a pointer, combined with the right () to indicate that it is a function, in conjunction with the leftmost void, indicating that it is a function pointer.

2) using a typedef to define void (*_f) () to facilitate the analysis of the following

Typedef void (*f) ()

3 So the code above can be turned into the following form
Static Void (*__set_malloc_handler (f)) ()

4 and then from the outside analysis __set_malloc_handler (f F) First and () combined to indicate that it is a function, the parameter type F, and then to the left of the * binding, indicating that the function returns a pointer type, that is, static void (*) (), so is a function pointer

5) can get the code function named __set_malloc_handler, accept a return value is NULL, the parameter is NULL function pointer as a parameter, and finally return a function pointer, the same return value and parameters are null, very around the mouth:

For example 2 analysis is as follows
1 from inside to outside is void (* handler) (int) Read the 1, it is easy to know that this is a function pointer, the return value is null, the argument is empty

2 to make a macro definition of void (*handler) (int) to facilitate understanding
Typedef Void (*handle) (int)

3) So the function becomes void (*signal (Intsig_num,handler Handler)) (int)

4 from the Inside Outward analysis signal (int sig_num,handlerhandler) is a function, with two parameters, the return value is *, that is a pointer, the return value of void (*) (int) is also a function pointer of a handler type

5 To sum up, the function name of code 2 is signal, accept two parameters, return a function pointer of handler type.

Other code analysis is similar to the following examples:

Copy Code code as follows:


1:void * (* (*f) (int)) [10];


analysis is as follows (* (*F) (int)-&gt;void * (*) [10]


2:void * (*f) (int) [10]


analysis is as follows (*F) (int)-&gt;void *[10]

And some of them are basically similar deformations.