Do I need to use "void" parameter?

[mac]

I'm reading a chapter of my book, but in the examples it lists

Code: Select all

int variable(void)

instead of omitting the parameter when there is none.

Should this be redundant? Should I follow it anyway since it's written in the book?

[iansjack]

Try compiling this snippet of code:

Code: Select all

void test()
{
};

void test2(void)
{
};

int main(void)
{
        test(3);
        test2(3);
}

What error(s) do you get? Can you see why it might be better to use the "void" declaration?

[matt11235]

If you don't specify any parameters, it will allow you to call the method with anything as a parameter.
By putting void, you're telling it not to do that.

[mac]

Try compiling this snippet of code:
...
What error(s) do you get? Can you see why it might be better to use the "void" declaration?

Yes, I definitely see that.

Output:
"error: too many arguments to function 'test2' "

[Geri]

you dont have to use it

[Sik]

I can definitely see where the confusion comes from.

For function declarations in C, leaving nothing between parenthesis tells the compiler to not bother checking, meaning it'll take anything (bad idea!), so you need to pass void to explicitly tell the compiler that it takes nothing instead. I don't remember if newer versions of the language change this behavior to be like C++'s (see below).

In C++, leaving the parenthesis empty means exactly not taking any arguments (as if you had passed void).

In other words: welcome to some legacy quirk from old language implementations that stuck around for newer ones.

EDIT: tl;dr include it to be safe.

[Love4Boobies]

That "void" isn't a parameter. At any rate, what you're looking at are old-style declarations. Before C89 got standardized, C used to only work like this:

Code: Select all

void foo();

void foo(x, y)
int x;
char y;
{
    // bla bla bla
}

Although they're still around so as not to break legacy code, you don't want to use them because your arguments will have no type checking.

[obiwac]

I can definitely see where the confusion comes from.

For function declarations in C, leaving nothing between parenthesis tells the compiler to not bother checking, meaning it'll take anything (bad idea!), so you need to pass void to explicitly tell the compiler that it takes nothing instead. I don't remember if newer versions of the language change this behavior to be like C++'s (see below).

In C++, leaving the parenthesis empty means exactly not taking any arguments (as if you had passed void).

In other words: welcome to some legacy quirk from old language implementations that stuck around for newer ones.

EDIT: tl;dr include it to be safe.

Why is it a necessarily bad idea? It works either way.

[iansjack]

Why is it a necessarily bad idea? It works either way.

Because the two appear to mean the same, but actually have very different meanings.

[obiwac]

Oh ok.