Is there a guarantee of stdout auto-flush before exit? How does it work?

Question

Here is the code (valid C and C++)

#include 

int main() {
    printf(\"asfd\");
    // LINE 1
    return 0;
}

If in line 1

Answer 1

This is accomplished by these two sections in the C++ language specification:

[basic.start.main]

A return statement in main has the effect of leaving the main function and calling exit with the return value as the argument.

and

[lib.support.start.term]

The function exit has additional behavior in this International Standard:

• ...
• Next, all open C streams with unwritten buffered data are flushed.
• ...