semicolon after the for loop block

Question

#include <iostream>

int main() {
    for( int i = 0; i < 5; ++i) {
        std::cout << "Hello" << std::endl;
    };
}

Is there any case that the semicolon after the for loop would affect the program ?

You could add 100 semicolons and it wouldn't have an effect. Would probably result in identical compiled code. — Carcigenicate, Jun 06 '17 at 15:19
Off topic, but It can be useful inside a `switch` nevertheless. Check the third answer of [this topic](https://stackoverflow.com/questions/92396/why-cant-variables-be-declared-in-a-switch-statement) if it interests you. — Badda, Jun 06 '17 at 15:24
This doesn't address the question, but do you really need the extra stuff that `std::end` does? `'\n'` ends a line. — Pete Becker, Jun 06 '17 at 23:54

dbush · Accepted Answer · 2017-06-06T15:30:54.007

1

The semicolon is an empty expression statement.

From section 6.2 of the C++ standard

The expression is a discarded-value expression (Clause 5). All side effects from an expression statement are completed before the next statement is executed. An expression statement with the expression missing is called a null statement. [ Note: Most statements are expression statements — usually assignments or function calls. A null statement is useful to carry a label just before the } of a compound statement and to supply a null body to an iteration statement such as a while statement (6.5.1). —end note ]

This will be more clear with some reformatting:

#include <iostream>

int main(){
    for(int i=0; i<5; ++i){
        std::cout <<"Hello"<<std::endl;
    }
    ;
}

The presence of this null statement has no effect on the program.

edited Jun 06 '17 at 15:30

answered Jun 06 '17 at 15:20

dbush

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Let's cite the C++ standard when the question is about C++. – Lightness Races in Orbit Jun 06 '17 at 15:21
1

@BoundaryImposition The question was tagged for both, so I initially went with C. The code itself is obviously C++, so I removed the C tag and changed the reference. – dbush Jun 06 '17 at 15:24
@dbush thank you for the answer – Konstantinos Mavrogiannis Jun 06 '17 at 15:33
@dbush: Good stuff. Unfortunately, C++ only tells us what the construct is called. – Lightness Races in Orbit Jun 06 '17 at 17:11

score 0 · Answer 2 · answered Jun 06 '17 at 15:19

0

No.

The semicolon is not even "attached" to the loop; it's just an empty statement sitting there, effectively on its own.

answered Jun 06 '17 at 15:19

Lightness Races in Orbit

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I don't know why recent GCCs don't warn on this; IME, older ones did. – Lightness Races in Orbit Jun 06 '17 at 15:20
clang-tidy will hepfully point it out. – Jesper Juhl Jun 06 '17 at 15:34

score 0 · Answer 3 · answered Jun 06 '17 at 15:20

0

It doesn't change anything. It just evaluates to an empty statement.

It's completely harmless. Just a bit of pointless clutter.

answered Jun 06 '17 at 15:20

Jesper Juhl

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semicolon after the for loop block

3 Answers3