significance

[nkumar85]

Hi,

I have seen in many of open source codes the do-while(0). Can anybody let me know when this is useful and whats the significance of constructing such code?

do
{
...........
...........
}while(0);

[Disch]

It allows you to mimic a goto command. Personally I find it pretty sloppy:

do
{
  if(something)
  {
    continue;  // exits the loop
  }

  if(something_else)
  {
    break;  // also exits the loop
  }
}while(0);

[rapidcoder]

Using break and continue is sloppy; while(0) or while(1) are just a consequences of it ;)

[kooth]

The do-while construct is useful when you want to run something at least once, and in this case, only once, because the while( 0 ) will end the do-while.

[1yR4jE8b]

@Disch
I'd rather just use goto instead of that monstrosity.

[Disch]

rapidcoder wrote:

Using break and continue is sloppy;

It's true they can be sloppy, that isn't to say they're always sloppy. Often times they are very practical.

kooth wrote:

The do-while construct is useful when you want to run something at least once, and in this case, only once, because the while( 0 ) will end the do-while.

The thing is, if you want something to run once and only once, you don't need any loop at all. Which is why the do{}while(0); construct is kind of ridiculous.

[nkumar85]

Hi All,

Thank you for the participation.

I found links on this.

http://c2.com/cgi/wiki?TrivialDoWhileLoop
http://stackoverflow.com/questions/154136/why-are-there-sometimes-meaningless-do-while-and-if-else-statements-in-c-c-macr


So one reason is what Disch said about.
One more reason is to keep code tidy, i.e. to allow semicolon after MACRO in some cases.

Refer links for details

[Duthomhas]

It is also very useful in macro expansions...