[Home]  [Edit this page]  [Recent Changes]  [Special Pages]  [Help] 

---

CppVoid

---

(C++) void

Keyword denoting that either

• The function returns nothing
• The function takes no arguments (in C)
• The function takes no arguments (in C++)
• The function returns a pointer of unknown type.

The function returns nothing

void sayHello()
{
  std::cout << "Hello world" << std::endl;
}

The function takes no arguments (in C)

(From the C++ MessageBoard, http://www.programmersheaven.com/c/MsgBoard/read.asp?Board=3&MsgID=339047&Setting=P0030F0001, thanks to stober)

In C, int myFunction(void); is the declaration of a function taking no arguments. In C++, int myFunction(); is preferred (see below) to specify this. In C, however, there is a difference between the two, as in C, int myFunction(); denotes a function declaration taking ANY number of unspecified parameter.

Here a (modified) example submitted by stober:

void func1();
void func2(void);
int main()
{
  int a = 0;
  int b = 0;
  func1();
  func1(a);  
  func1(a,b);
  func2(a); //Error on this line! func2 has no arguments!
}

The function takes no arguments (in C++)

This is called 'an abomination' by Bjarne Stroustrup (the creator of C++), Dennis Ritchie, the co-creator of C, and Doug McIlroy, head of the research department where Unix was born [1,3]. In [1] Bjarne Stroustrup gives the following code as example:

int f(void) ; // error: abomination
int g() ; // g takes no argument

The function returns a pointer of unknown data type

void* someFunction();

( Sorry, I haven't got a better example. I need to look in some Win32 API for one).

Avoid void* except in low-level code [2]

See void* for more details.

'void' links

• C
• C#

References

• 1) Bjarne Stroustrup. 2002. Sibling rivalry: C and C++. The C/C++ Users Journal of July, August and September 2002.
• 2) Bjarne Stroustrup. The C++ Programming Language (3rd edition).ISBN: 0-201-88954-4 Chapter 5.8.7: 'Avoid void* except in low-level code'.
• 3) http://www.parashift.com/c++-faq-lite/newbie.html#faq-29.4

[Edit this page]  [Page history]  [What links here]  [Discuss this topic]  [Printer Friendly]