About typedef -- define the function pointer or define function model?

[robin liu]

What's the difference between these two declarations ?

1) typedef void (*pf)(void);
2) typedef void f(void);

the first declaration is define a function pointer, what is the second ?
define a function model?

And can use the second declaration to define a function pointer as follow:

typedef void f(void);
f *pf;

Whether the two declarations of pf1 are both pointer to a function?

1) typedef void (*pf)(void);
pf pf1;
2) typedef void f(void);
f *pf1;

if yes, which is better? and I saw many codes used the second declaration,
what is its' advantage or disadvantage?


Thanks in advance!



(e-mail address removed) from china

 

[Richard Heathfield]

robin liu said:

What's the difference between these two declarations ?

1) typedef void (*pf)(void);
2) typedef void f(void);

the first declaration is define a function pointer,

No, it defines a synonym for an existing function pointer type.

what is the second ? define a function model?

No, it defines a synonym for an existing function type.

And can use the second declaration to define a function pointer as follow:

typedef void f(void);
f *pf;
Yes.

Whether the two declarations of pf1 are both pointer to a function?

1) typedef void (*pf)(void);
pf pf1;
2) typedef void f(void);
f *pf1;
Yes.

if yes, which is better? and I saw many codes used the second declaration,
what is its' advantage or disadvantage?

The advantage of the second is that it does not hide a pointer
characteristic inside a typedef. The * reminds us that here be dragons,
which can be a useful hint. So I use the second form.

 

[robin liu]

Thank Richard very much!!

And your explaination is very detailed and clear. According to it, I think
I have understand the different between the two declarations
and I believe I can use them better from now.

Thanks again!!

 

[Robin Liu]

After review my post news, I found that I make a big mistake.

Thanks to richard, you are right. The first declaration I said defines a
synonym for an existing function
pointer type, and the second defines a synonym for an existing function
type.

Thanks and apologize for my mistake once again !!