c - Why no semicolon gives errors but too many of them don't?

Question

Consider this C code:

#include <stdio.h>;

int main(void) {
    puts("Hello, world!");; ;
    ;
    return 0; ;
    ; ;
};

Here I've put semicolons almost everywhere possible. Just for fun. But surprisingly it worked! I got a warning about the semicolon after include but other absolutely wrong semicolons worked. If I forget to put a semicolon after puts, I'll get the following error

error: expected ';' before 'return'

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Why don't lots of wrong and useless semicolons cause errors? To my mind they should be treated as syntax errors.

Answer 1

A single semicolon constructs a null statement. It's not only legal, it's also useful in some cases, for instance, a while/ for loop that doesn't need a real body. An example:

while (*s++ = *t++)
    ;

C11 6.8.3 Expression and null statements

A null statement (consisting of just a semicolon) performs no operations.

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The only syntax error is this line:

#include <stdio.h>;