Why doesn't this code show the "reached out of memory" error here?

Question

I tried to reach out of the array's memory in my compare function. To my surprise, it works, however, I think there should be a memory error. Could someone have a look and give me an answer?

#include <stdio.h>
int string_compare(const char* w1, const char* w2, unsigned int len){
    for(int i = 0; i < len; i++){
        if(w1[i] != w2[i]){
            return 0;
        }
    }
    return 1;
}
int main(){
    printf("%d\n",string_compare("Hello'\0' world!", "Hello",10));
}

Answer 1

It works, while I think there should be a memory error.

There is no memory error.

Compare stops at index since w1[5] != w2[5] is true. w1[5] is a ', not a null character.

---

Perhaps OP wanted to compare "Hello\0 world!", "Hello"?

Now that will have trouble with index6, which is beyond "Hello" and incurs undefined behavior. "It works," might happen, might fail, It is UB.

---

A proper string compare would stop when character differ or a null character is detected.

// if(w1[i] != w2[i]){
if(w1[i] != w2[i] || w1[i] == 0){