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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!



from china

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.

--
Richard Heathfield
"Usenet is a strange place" - dmr 29/7/1999
http://www.cpax.org.uk
email: rjh at above domain (but drop the www, obviously)

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!!


"Richard Heathfield" <> ????
news:LKadne-...
> 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.
>
> --
> Richard Heathfield
> "Usenet is a strange place" - dmr 29/7/1999
> http://www.cpax.org.uk
> email: rjh at above domain (but drop the www, obviously)

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 !!




"Richard Heathfield" <> ????
news:LKadne-...
> 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.
>
> --
> Richard Heathfield
> "Usenet is a strange place" - dmr 29/7/1999
> http://www.cpax.org.uk
> email: rjh at above domain (but drop the www, obviously)