CODEWITHSUNDEEP
c++
REA_ANDREW
REA_ANDREW

Reputation: 10764

What is the meaning of having void in the constructor definition?

Given the following code:

#pragma once

class B
{
public:

    B(void)
    {
    }

    ~B(void)
    {
    }
};

I know I can also write this:

#pragma once

class B
{
public:

    B()
    {
    }

    ~B()
    {
    }
};

What is the purpose of having void in the first example? Is it some type of practice that states the constructor take zero parameters?

Upvotes: 17

Views: 14883

Answers (4)

TofuBeer
TofuBeer

Reputation: 61536

A long time ago you did something like this in C (my pre-ISO C is rusty :) ):

void foo(a, b)
   int a, 
   int b
{
}

while C++ was being created the name mangling required the types of the arguments, so for C++ it was changed to:

void foo(int a, int b)
{
}

and this change was brought forward to C.

At this point, I believe to avoid breaking existing C code this:

void foo()

and this:

void foo(void)

meant two very different things, () means do not check for the argument number or type, and (void) means takes no arguments. For C++ () meaning not to check anything was not going to work so () and (void) mean the same thing in C++.

So, for C++ () and (void) were always the same thing.

At least that is how I remember it... :-)

Upvotes: 11

JD Isaacks
JD Isaacks

Reputation: 57994

I just wanted to add that when you use void after the parameters like function():void it is used to indicate that the function does not return a value.

Upvotes: 0

dirkgently
dirkgently

Reputation: 111200

The two are same, at least in C++. In C, providing an empty pair of parentheses typically means an unspecified parameter list (as opposed to an empty parameter list). C++ does not have this problem.

How can a correct answer get downvoted so many times? Yet another SO bug?

Upvotes: 45

Annerajb
Annerajb

Reputation: 932

afaik if you pass void into the constructor or any function as the argument it means that the function dosnt take any argument so example a and b are equal. but i am not sure if any of them change the function signature in any way or make it run faster etc.

Upvotes: 0

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