In C/C++ why does the do while(expression); need a semi colon?

Question

My guess is it just made parsing easier, but I can't see exactly why.

So what does this have ...

do
{
  some stuff
}
while(test);

more stuff

that's better than ...

do
{
  some stuff
}
while(test)

more stuff

Answer 1

Because you're ending the statement. A statement ends either with a block (delimited by curly braces), or with a semicolon. "do this while this" is a single statement, and can't end with a block (because it ends with the "while"), so it needs a semicolon just like any other statement.

Answer 2

While I don't know the answer, consistency seems like the best argument. Every statement group in C/C++ is either terminated by

1. A semicolon
2. A brace

Why create a construct which does neither?

Answer 3

In C/C++ whitespace don't contribute to structure (like e.g. in python). In C/C++ statements must be terminated with a semicolon. This is allowed:

do
{
  some stuff; more stuff; even more stuff;
}
while(test);

Answer 4

C is semicolon-terminated (whereas Pascal is semicolon-separated). It would be inconsistent to drop the semicolon there.

I, frankly, hate the reuse of the while for the do loop. I think repeat-until would have been less confusing. But it is what it is.

Answer 5

It's because while statements are valid within a do-while loop.

Consider the different behaviors if the semicolon weren't required:

int x = 10;
int y = 10;

do 
  while(x > 0)
    x--;
while(x = y--);