Adding a `;` at the end of while loop

Question

#include<stdio.h>

int main()
{
    int i=5;
    while(i--)
    {
        printf("%d\n",i);
    };
    printf("Out of loop\n");
    return 0;
}

This code works fine! Does ; at the end of a loop not mean anything? So even if we add it, we don't have any problems? Just curious! I think adding ; at the end of a loop doesn't make any sense.

the extra `;` is the termination of an "empty statement". Adding `;;` after the `}` would add two empty statements. — wildplasser, Dec 03 '14 at 10:57
Note that, in `do { /* code */ } while ( /* condition */ );`, the trailing `;` is *not* an empty statement, but required. — DevSolar, Dec 03 '14 at 11:06

score 10 · Accepted Answer · answered Dec 03 '14 at 10:59

It "works", but it's an empty statement so it changes the structure of your program.

Consider this:

if (foo())
  while (bar())
  {
    foo_some_more()
  }
else
{
  do_something_about_it();
}

The above works since the while is a single statement, and thus the else is still able to "find" the if properly. If you add a semi-colon after the while-loop's closing brace, you break that structure and it will no longer compile.

So, although empty statements can look harmless, they are not so they really should be avoided. Plus: they add pointless confusion to the code, of course.

score 6 · Answer 2 · edited May 23 '17 at 12:32

6

The ; here is considered as an empty statement or null statement.

Sample

int i = 0;;

For more information, you can check this question.

^{Word of Caution: Don't consider this as a thumb rule. There are cases where the representation may appear same, but they are not null statement but part of a syntax. Example: do..while loop}

edited May 23 '17 at 12:32

Community

1
1

answered Dec 03 '14 at 10:56

Natasha Dutta

3,242
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Bathsheba · Answer 3 · 2014-12-03T11:14:33.857

4

A superfluous ; is an empty statement and is redundant in this particular instance.

One instance where you're required to use an empty statement is in a switch to a final branch that does nothing:

switch (expression)
{
    case 1:
       /*Some statements here or empty*/
    case 2:
    ;  /*A statement is required between here and the closing brace
         An empty statement will suffice.*/
}

You ought to avoid using superfluous empty statements; they can emit bugs (particularly if you enclose your code in if statements during a refactoring effort), and older compilers will complain. Using excess semicolons in macros is particularly pernicious.

edited Dec 03 '14 at 11:14

answered Dec 03 '14 at 11:01

Bathsheba

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Errr... how is the semicolon required there? – DevSolar Dec 03 '14 at 11:05
Try compiling without it ;-) – Bathsheba Dec 03 '14 at 11:06
I put in another case. Principle still holds though. – Bathsheba Dec 03 '14 at 11:10
@DevSolar True, but there must be a statement between the last case and the closing brace. – Klas Lindbäck Dec 03 '14 at 11:11

score 1 · Answer 4 · answered Dec 03 '14 at 12:09

1

These are Perfectly Valid, They are called Empty statements,They do nothing.

int main()
{
  ;
  ;
  ;
  ;
  {
  }
  return 0;
}

answered Dec 03 '14 at 12:09

Mysterious Jack

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score 0 · Answer 5 · answered Dec 03 '14 at 14:16

As stated by various users above, the relevant semi-colon is an empty statement and has no effect.

This however is a slightly different story:

#include <stdio.h>

int main()
{
    int i=5;    
    while(i--); //<--- Put the semi-colon here and see what you get.
    {
        printf("%d\n",i);
    }    
    printf("Out of loop\n");    
    return 0;   
}

score 0 · Answer 6 · edited Jan 10 '15 at 18:31

0

#include<stdio.h>

int main()
{

    int i=5;
    while(i--)
    {
        printf("%d\n",i);
    }/*blank statement*/;
    printf("Out of loop\n");
    return 0;
}

it's just a blank statement. above The braces itself tells end of the block so then it would treat the ; as blank stament

edited Jan 10 '15 at 18:31

Rizier123

58,877
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answered Jan 07 '15 at 06:51

Janakiram Reddy

85
3
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Adding a `;` at the end of while loop

6 Answers6