What is the use of while(0) statement in C?

Question

While(0) means dont enter into it, but why you want to have while(0) in c code. Any suggestion.

Asked in the interview today.

Answer 1

You are right. But some times while(0) (do ... while(0)) is used for error checking and to avoid deep nested if's.
Typical C Style coding as we dont have exception in C.

Example:
do {
// do something
if (error) {
break;
}
// do something else
if (error) {
break;
}
// etc..
} while (0);

Answer 2

As Pushkar pointed out while(0){} is a null statement and is not used and even if you use compiler may optimize it. The only case is do..while(0) where one more possibility is the following (Credit: SO)

#define FOO(x) { foo(x); bar(x); }

Using this in an if statement would require that you omit the semicolon, which is counterintuitive:

if (condition)
    FOO(x)
else
    ...

If you define FOO like this:

#define FOO(x) do { foo(x); bar(x); } while (0)

then the following is syntactically correct:

if (condition)
    FOO(x);
else
    ....