Identify Trap in Signed vs Unsigned Comparison

#include <stdio.h>
#include <stdint.h>

int safe_compare(int8_t a, uint8_t b) {
    // Your logic here
    if(a & 0x80) return 1; // Since b is a uint8_t number it can never be less than zero.

    return (a<b) ? 1 : 0;
}

int main() {
    int8_t a;
    uint8_t b;
    scanf("%hhd %hhu", &a, &b);
    printf("%d", safe_compare(a, b));
    return 0;
}