c++有符号变量和无符号变量相加的结果

#include <stdio.h>

char getChar(int x,int y)
{
    char c;
    unsigned int a = x;
    (a+y>10)?(c=1):(c=2);
    return c;
}

int main()
{
    char c1 = getChar(7, 4);
    char c2 = getChar(7, 3);
    char c3 = getChar(7, -7);
    char c4 = getChar(7, -8);
    
    printf("c1=%d\n",c1);
    printf("c1=%d\n",c2);
    printf("c1=%d\n",c3);
    printf("c1=%d\n",c4);
    return 0;
    
    
}