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

When main() exits, all open streams are closed... to include stdout. Closing the open stream flushes stdout and what you've written to the buffer gets committed with or without the newline.