C上strcmp（）中的分段错误

Question

My program to compare strings fails with Segmentation Fault after the second input:

#include<stdio.h>

#include<string.h>

int main (void)

{       
    char* input1;
    char* input2;
    printf("type something: ");
    scanf("%s", &input1);

    printf("type something: ");
    scanf("%s", &input2);

    if(strcmp(input1, input2) == 0)
    {
        printf("u type the same thing\n");  
    }
    else
    {
        printf("u not type the same thing\n");
    }

}

output:

sekai92@sekai92-VirtualBox:~/Desktop/C_CPP$ make compare
clang -Wall -Werror -ggdb     compare.c   -o compare
sekai92@sekai92-VirtualBox:~/Desktop/C_CPP$ ./compare 
type something: hello
type something: hello
Segmentation fault (core dumped)

Answer 1

input and input1 are uninitialized pointers. This causes to undefined behaviour (C language standard term).

You need to allocate meory using malloc() or calloc() . Or simply use local arrays:

char input[SIZE]; 
char input1[SIZE];