Answer to question 4.8 from the FAQ

[=?ISO-8859-15?Q?Jean=2DFran=E7ois?= Lemaire]

Hello,

In the answer to question 4.8 I see this code (copied and pasted):

-------------------------
void f(ipp)
int **ipp;
{
static int dummy = 5;
*ipp = &dummy;
}
....

int *ip;
f(&ip);
-------------------------

I'm confused about the two first lines. Should'nt the first one be
written 'void f(**ipp)' and the second one scrapped altogether?

If not, I don't understand how the above can be legal.

JFL
--
Jean-François Lemaire

[Eric Sosman]

Jean-François Lemaire wrote:

Hello,

In the answer to question 4.8 I see this code (copied and pasted):

-------------------------
void f(ipp)
int **ipp;
{
static int dummy = 5;
*ipp = &dummy;
}
...

int *ip;
f(&ip);
-------------------------

I'm confused about the two first lines. Should'nt the first one be
written 'void f(**ipp)' and the second one scrapped altogether?

ITYM `void f(int **ipp)'.

If not, I don't understand how the above can be legal.

Question 11.3 has a useful hint, and 11.4 is worth
a look, too.

--
Er*********@sun.com

[=?ISO-8859-15?Q?Jean=2DFran=E7ois?= Lemaire]

On Friday 4 January 2008 17:28, Eric Sosman wrote:

Jean-François Lemaire wrote:

>In the answer to question 4.8 I see this code (copied and pasted):

-------------------------
void f(ipp)
int **ipp;
{
static int dummy = 5;
*ipp = &dummy;
}
...

int *ip;
f(&ip);
-------------------------

I'm confused about the two first lines. Should'nt the first one be
written 'void f(**ipp)' and the second one scrapped altogether?

ITYM `void f(int **ipp)'.

IID (Indeed I Did).

>If not, I don't understand how the above can be legal.

Question 11.3 has a useful hint, and 11.4 is worth
a look, too.

OK, I understand now. I'm not used to reading the old style syntax and
would have never thought it was simply that.

Thanks for pointing me in the right direction.

JFL
--
Jean-François Lemaire

[Keith Thompson]

Jean-Francois Lemaire <jf*******@skynet.bewrites:

In the answer to question 4.8 I see this code (copied and pasted):

-------------------------
void f(ipp)
int **ipp;
{
static int dummy = 5;
*ipp = &dummy;
}

[...]

That's an old-style function definition; it predates the ANSI
standard, but it's still permitted, even in C99.

What I don't know is why the FAQ still uses it here. I see no good
reason not to use a prototype. Probably it's just an oversight. I've
sent e-mail to Steve Summit.

(Sorry about mangling your name; this environment isn't handling
non-ASCII characters very well.)

--
Keith Thompson (The_Other_Keith) <ks***@mib.org>
[...]
"We must do something. This is something. Therefore, we must do this."
-- Antony Jay and Jonathan Lynn, "Yes Minister"

[=?ISO-8859-15?Q?Jean=2DFran=E7ois?= Lemaire]

On Friday 4 January 2008 21:26, Keith Thompson wrote:

Jean-Francois Lemaire <jf*******@skynet.bewrites:

>In the answer to question 4.8 I see this code (copied and pasted):

-------------------------
void f(ipp)
int **ipp;
{
static int dummy = 5;
*ipp = &dummy;
}

[...]

That's an old-style function definition; it predates the ANSI
standard, but it's still permitted, even in C99.

What I don't know is why the FAQ still uses it here. I see no good
reason not to use a prototype. Probably it's just an oversight. I've
sent e-mail to Steve Summit.

Yes, this can be confusing for new users of the language, the intended
audience of the FAQ, who are less likely to have encountered such a
function definition. At least it was confusing for me.

(Sorry about mangling your name; this environment isn't handling
non-ASCII characters very well.)

No excuse needed, I can assure you.

JFL
--
Jean-François Lemaire