#include <stdio.h>


int main () {
    int vIn_a, vIn_b, vIn_c;
    char vOperator;

    
    printf("Please enter a number\n");
    scanf("%d", vIn_a); 
    printf("Please enter a number\n");
    scanf("%d", vIn_b);
    printf("Please enter a Operator\n");
    scanf("%c", vOperator);

    switch(vOperator){
        case ' ':
            vIn_c = (vIn_a   vIn_b); 
            break;
        case '-':
            vIn_c = (vIn_a - vIn_b);
            break;
        case '/':
            vIn_c = (vIn_a / vIn_b);
            break;
        case '*':
            vIn_c = (vIn_a * vIn_b);
            break;
    }
    printf("Result: %d %c %d = %d", vIn_a, vOperator, vIn_b, vIn_c);
    return 0;
}

Just trying to figure this out, i ran gdb. But not sure what my debugger is telling me at this point. Maybe im overlooking it? Debugger: Program received signal SIGSEGV, Segmentation fault. 0x00007ffff7c60d36 in ?? () from /usr/lib/libc.so.6

So what is causing this segmentation fault guys? Im learning C and im lost.

Thanks in advance.

CodePudding user response：

When you use scanf(), you don't pass the variable into which you want to store the value, you pass a pointer to the variable.

So, for instance, instead of scanf("%d", vIn_a);, you need scanf("%d", &vIn_a); - note the '&'!

The effect of the scanf() calls, as you wrote them, was to pass an arbitrary number (whatever random content was in the uninitialised vIn_a and vIn_b) into scanf(). It treated those random(ish) integer values as pointers. So when it wrote the user-contributed value into the "pointer" it has been passed, it had the effect of:

*(int *)vIn_a = user_entered_value;

If you know your way around pointers, you'll know this is a recipe for disaster!

There are two more gotchas:

1. Your '/' operator doesn't check whether its divisor (vIn_b) is zero, so it would be easy to crash with a divide-by-zero error if the user selected zero for vIn_b and '/' for the operator.

2. You don't have a default: clause in your switch statement, so if the user types something other than the operator characters you're checking for, vIn_c will contain random rubbish as it's uninitialised by the time it's printed.

CodePudding user response：

You can use scanf function with &. For example; scanf("%d", &vIn_a);

For documentation : https://cplusplus.com/reference/cstdio/scanf/