#include <stdio.h>
#include <stdlib.h>
#include <stdbool.h>
#include <assert.h>

#define dbg_log(n) (printf("%s == %d\n", (#n), (n)))

int double_it(int n) {
    // return n * 2;   // normal way
    int n_times_2 = n;
    for(int i = 0; i <= n; i++) {   // BUG!!!  «i <= n»  should be «i < n»
        n_times_2 += 1;
        dbg_log(i);         // becomes (printf("%s == %d", ("i"), (i)))
        dbg_log(n_times_2);
        dbg_log(n);
        dbg_log(n * 2);     // becomes (printf("%s == %d", ("n * 2"), (n * 2)))
    }
    return n_times_2;
}

int main(int argc, char* argv[]) {
    printf("double_it(5) == %d\n", double_it(5));
    return EXIT_SUCCESS;
}
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