CODEWITHSUNDEEP
cscanf
zg303
zg303

Reputation: 97

Why is sscanf acting this way?

I thought that I understood C but i am having a hard time just writing a simple addition code for practice. When I run this code, int a is 0 every time. However, int b works fine. The idea here is that the input to the program is 8 + 9. Why does sscanf not recognize variable a?

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

int plus(int a, int b){
    return (a + b);
}

int main()
{
    int a, b;
    char input[100], op;

    printf("...I am ZOLO...\n");
    printf("...The most vercatile calculator known to man...\n");
    printf("...Please enter your query:");
    fgets(input, sizeof(input), stdin);
    sscanf(input, "%d %s %d", &a, &op, &b);

    printf("%d + %d = %d...", a, b, plus(a, b)); 

    return 0;
}

Upvotes: 0

Views: 133

Answers (1)

torek
torek

Reputation: 488183

Jonathon Reinhart has the correct answer. In this case, it's not just the undefined behavior problem, it's the fact that the compiler managed to allocate op just before a (in internal memory order) and your machine uses little-endian byte order so that the '\0' character stored after op wipes out the value that was previously stored to a.

Upvotes: 1

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