I took a C Advanced Course on Udemy, and there is a question from there: What will be the output of the following code?

#include <stdio.h>

int main(void){
    static int i=5;
    if(--i){
        main();
        printf("%d ", i);
    }
}

The right answer is 4 3 2 1, but when I run this code in my IDE (and online compilers), it prints 0 0 0 0. In the course lector uses cygwin compiler and I have g . May it be the reason of the inconsistency? Also I'm wondering if if(--i) method is faster then for loop by the concept of performance?

Thank you.

CodePudding user response：

The posted code shall print 0 0 0 0 because the printf is after the recursive call, i.e.

    main();            // Recursive call
    printf("%d ", i);  // Print after

If you instead do:

    printf("%d ", i);  // Print before
    main();            // Recursive call

the output will be 4 3 2 1

So I think your lector used the last form and you used the first form, i.e. different code, different results

CodePudding user response：

The reason is main() is called before printf("%d ", i). So when if block is executed, main() function is called before printing the value of i and it's continue to do so until if-condition is false. Here if-condition became false when i is equal to 0. When the if-contidion is false the function return to the previous state from where it have been called and then print the value of i, which is now 0.

To print 4 3 2 1, print the values before calling main() funtion like bellow

int main(void){
static int i=5;
if(--i){
    printf("%d ", i);
    main();
}

}