Re: Strange function use

On Thu, 03 Aug 2006 12:17:14 +0200, Christian Christmann
<plfriko@xxxxxxxx> wrote in comp.lang.c:

On Thu, 03 Aug 2006 02:51:39 -0700, lovecreatesbeauty wrote:


Christian Christmann wrote:
1 int foo( int f )
2 {
3 return f;
4 }
5
6 int main( void )
7 {
8 int a, b, foo();

int a, b, foo( int );

9 a = 10;
10 b = foo( a );
11
12 return 0;
13 }

I don't understand the use of function "foo" in line 8.
What's it's purpose? It's called without assigning it's
return value to any variable. Furthermore, I wonder
return value to any variable. Furthermore, I wonder
why this function use is allowed at all. According to
the function prototype "foo" expects an integer argument
that is in line 8 not given. Compiling the code with
"gcc -Wall -ansi" does not issue any warning/errors.

int foo( ); /*int foo( int );*/

It's not a function use/call, foo() occurs inside a declaration. It's a
function prototype declaration.

But it's a declaration that deviates from the declaration
given in line 1. There's no function "foo" defined without
any parameters, so why is the declaration from line 8
accepted by a compiler?

Part of your confusion is based on a misunderstanding of this:

int foo(int);

....regardless of the fact that it as at block scope rather than file
scope.

The declaration (not prototype) above declares foo to be a function
that returns an int and accepts an unspecified but fixed number and
type of arguments.

It most specifically is NOT a prototype for a function that takes no
arguments. In another language that stole much of an earlier version
of C, these two declarations are equivalent:

int foo();
int foo(void);

....that is not the case in real, genuine, C.

--
Jack Klein
Home: http://JK-Technology.Com
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