strcpy函数，带有指向字符数组的指针

Question

In the code below the result is stack overflow. Though null character is there with both the strings, so the strcpy loop should terminate as the source string has null character. Why stack overflow occurs??

#include <stdio.h>
#include<strings.h>
int main(void) {
    char *str="Hello world";
    char *str1="Good morning";
    strcpy(str,str1);
    printf("%s",str);
    return 0;
}

Answer 1

The error isn't stack overflow, but modifying a string literal.

str is a pointer that points to a string literal "Hello world" , and modifying a string literal is undefined behavior.

Change str to:

char str[100] = "Hello world";