C: declaring void parameters

jrtayloriv · 02-11-2005, 01:54 PM

What does it mean when you pass type void to a C function? For instance when I say int init_module(void), does this do anything different than if I had just said int init_module()? Or, does it have some side effect that I need to know about?

thanks,
jrtayloriv

Hko · 02-11-2005, 02:03 PM

As far as I know, there's no difference, except for maybe old compilers didn't accept: int init_module().

jim mcnamara · 02-11-2005, 02:04 PM

No side effect - normal use is to call the function like this

Code:

foo();

Don't use the "void" part. Some compilers will not like it.

perfect_circle · 02-11-2005, 02:05 PM

Quote:

For instance when I say int init_module(void), does this do anything different than if I had just said int init_module()?

I think that it's basically the same when you write the body a function that does not have any arguments:
int func()
{

}.

But When you have a fuction,
let's say
int func(int a)
{...................
........................
.....................
........................
...............
}

You may declare it somewhere in a code or a header file as:
int func(); //you don't say nothing about the arguments, this is legal
but i think it is wrong to use:
int func(void); //this function has arguments and this is wrong.

This is what i think. I may be wrong

perfect_circle · 02-11-2005, 02:20 PM

basically this is what i mean:

Code:

skalkoto@darkstar:~$ cat code.c
#include <stdio.h>

int main()
{
        void func(void);
        func(3);
return 0;
}

void func(int a)
{
        printf("Nothing\n");
}
skalkoto@darkstar:~$ gcc code.c
code.c: In function `main':
code.c:6: error: too many arguments to function `func'
skalkoto@darkstar:~$ cat code1.c
#include <stdio.h>

int main()
{
        void func();
        func(3);
        return 0;
}

void func(int a)
{
        printf("Nothing\n");
}
skalkoto@darkstar:~$ gcc code1.c
skalkoto@darkstar:~$ ./a.out
Nothing
skalkoto@darkstar:~$

when you declare somewhere a function func(), this means you don't say anything about it's aguments.
On the otherhand func(void) means NO ARGUMENTS

P.S. When i started learning c you could not use a function if the body of the function was in the same file but under
the calling point of the function without declaring the function above the calling piont. Nowdays gcc has not those problems.
I miss those old days, everything was so clear.