Semicolon at the ends of if-statements and functions in C

Question

I just ran into some code that overuse semicolons, or use semicolon for different purposes that I am not aware of.

I found semicolons at the end of if-statements and at the end of functions. For instance:

  int main (int argc, char * argv[]) {
       // some code

       if (x == NULL) {
           // some code
       };  <-----

       // more code

       return 0;
  }; <---

It is compiling with cc, not gcc. What do those semicolons do? I'm assuming that there is no difference because the compiler would just consider it as empty statement.

Answer 1

They do nothing. They're a sign of someone who doesn't understand the language terribly well, I suspect.

If this is source code you notionally "own", I would remove the code and try to have a gentle chat with the person who wrote it.

Answer 2

that's dummy statememt. You sample is identical to

if (x == NULL) {
 // some code
 do_something_here();
}

/* empty (dummy statement) here */ ;

// more code
some_other_code_here();

Answer 3

You are right, the compiler considers them empty statements. They are not needed, I guess the programmer somehow thought they were.

Answer 4

These semicolons are not needed (as you said, they are empty statements). Your code compiles with gcc, providing that 'x' is defined (check http://www.codepad.org). There's no reason why a C compiler would refuse to compile your code.

Answer 5

The first semicolon (after the if-statement) is just an empty expression which does nothing. I fail to see any point of having it there.

The second semicolon (after the function) is an error since it is outside of any block of code. The compiler should give a warning.

Answer 6

I think that the author may have been going for something like:

if(condition for tbd block)
    ;
else {
    //Some code here
}

which you might do if you were scaffolding code and still wanted it to compile. There's a good chance that it's just an error as Jon suggests though.

Answer 7

These semicolons are useless as others have pointed out already. The only thing I want to add is that IMO, these are optimized out anyway i.e., compiler doesn't generate any real code for these.