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Grumble wrote:

> Hello everyone,
>
> I've come across some strange code. Here it is, stripped down:
>
> int main(void)
> {
> int *foo;
> int *bar();
> foo = bar(0);
> return 0;
> }
>
> $ gcc-3.4.3 -c -Wall -ansi -pedantic -O mini.c
> /* NO WARNING */
>
> If I understand correctly, line 2 in main() is a function prototype
> which declares 'bar' as a function taking an unspecified number of
> parameters, and returning a pointer to int?
>
> Can function prototypes really appear anywhere in the code?

No. They are declarations, and declarations can't appear "anywhere".
But they can appear at block start, even in C89.

> I suppose the better way to write that code would be:
>
> int *bar();
> int main(void)
> {
> int *foo;
> foo = bar(0);
> return 0;
> }
>
> Would you agree?

I would agree, but that's a constraint of style, not language.

--
Chris "electric hedgehog" Dollin

Chris Dollin wrote:

> Grumble wrote:
>
>> I've come across some strange code. Here it is, stripped down:
>>
>> int main(void)
>> {
>> int *foo;
>> int *bar();
>> foo = bar(0);
>> return 0;
>> }
>>
>> If I understand correctly, line 2 in main() is a function prototype
>> which declares 'bar' as a function taking an unspecified number of
>> parameters, and returning a pointer to int?
>>
>> Can function prototypes really appear anywhere in the code?
>
> No. They are declarations, and declarations can't appear "anywhere".
> But they can appear at block start, even in C89.
>
>> I suppose the better way to write that code would be:
>>
>> int *bar();
>> int main(void)
>> {
>> int *foo;
>> foo = bar(0);
>> return 0;
>> }
>>
>> Would you agree?
>
> I would agree, but that's a constraint of style, not language.

In the first example, the function declaration only has block scope.

Thus, the following code is incorrect:

int main(void)
{
int *foo;
int *bar(int,int);
foo = bar(1,2);
return 0;
}

int *baz(void) { return bar(3,4); }

$ gcc-3.4.3 -c -Wall -ansi -pedantic -O1 toto2.c
toto2.c: In function `baz':
toto2.c:9: warning: implicit declaration of function `bar'

Do people actually use local function declarations?

--
Regards, Grumble

On Wed, 19 Jan 2005 15:32:10 +0100, Grumble <>
wrote:

>Chris Dollin wrote:
>
>> Grumble wrote:
>>
>>> I've come across some strange code. Here it is, stripped down:
>
>Do people actually use local function declarations?

Apparently they do, but don't ask me why. I have seen this often in a
particular body of legacy code I'm working with. A function handling a
file will often declare

FILE *fp, *fopen();

(That's before I clean them up, of course

--
Al Balmer
Balmer Consulting

In article <cslopn$hs0$>, Chris Dollin <> writes:
> Grumble wrote:
>
> > I've come across some strange code. Here it is, stripped down:
> >
> > int main(void)
> > {
> > int *foo;
> > int *bar();
> > foo = bar(0);
> > return 0;
> > }
> >
> > If I understand correctly, line 2 in main() is a function prototype
> > which declares 'bar' as a function taking an unspecified number of
> > parameters, and returning a pointer to int?
> >
> > Can function prototypes really appear anywhere in the code?
>
> No. They are declarations, and declarations can't appear "anywhere".
> But they can appear at block start, even in C89.

Not if they're declarations of functions with static linkage. See
ISO 9899-1990 6.5.1:

The declaration of an identifier for a function that has block
scope shall have no explicit storage-class specifier other than
extern.

(This is part of the semantics of storage-class specifiers, not a
constraint, so it's not required to produce a diagnostic.)

This means that you cannot prototype a static function at block
scope.

I agree with Chris that even for functions with external linkage,
declarations at block scope are a poor idea; they accomplish little
(in practice, it's rarely useful to restrict the scope of a function
identifier), and since the same can't be done for static-linkage
functions, you'd end up with inconsistent placement of prototypes,
which can't help readability.

--
Michael Wojcik

Viewers are bugs for famous brands.
-- unknown subtitler, Jackie Chan's _Thunderbolt_