Tricky typedef

What is the purpose of this?

typedef unsigned * (*item)(void* yyy);

cdecl: C gibberish <-> English
It's a function pointer.

What is the difference then between the a bove to the ordinary way?
The ordinary way is: typedef void (Item_t)(int)
What can be the usage of this?

Do you have some context for the question?

> What can be the usage of this?
Typedef'ing a function pointer is very common.

Primarily because they're quite complicated to get right, and they get very verbose in a hurry.
So summarising a whole bunch of ( ) and * into a single word makes good sense.


Typedef'ing a function is basically unheard of.

Trying to explain the declaration... This:

Code:

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unsigned int func( void *p );

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Is a function named func which returns an unsigned int and takes a pointer to void as argument, right?

This:

Code:

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unsigned int *func(void *p);

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Is the same, but returns a pointer to unsigned int. So, this other one is a pointer to a function which returns a pointer to unsigned int and takes a pointer to void as argument:

Code:

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unsigned int *(*funcptr)(void *);

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Now we can transform this declaration in a typedef:

Code:

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typedef unsigned int *(*funcptr_T)(void *);

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And use the type funcptr_T, instead of that complicated declaration, for example:

Code:

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typedef unsigned int *(*funcptr_T)(void *);

unsigned int *f( void *p ) { ... do something... }
unsigned int *g( void *p ) { ... do something else ... }

unsigned int *example( unsigned int n, void *arg )
{
  // table with pointers to functions.
  const static funcptr_T fptr[] = { f, g };

  if ( n < 2 )
    return fptr[n](arg);  // indirect call through a pointer.
  return NULL;
}

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Thanks flp1969, this is helpful