condition is false but even then its printing size of s

Question

#include<stdio.h>
#include<string.h>

void printlen(char *s,char *t){
    int c=0;
    int len=((strlen(s)-strlen(t)>c)?strlen(s):strlen(t));
    printf("%d",len);
}

void main(){

char *x="abc";
char *y="defgh";
   printlen(x,y);

}

strlen(s) is 3 and strlen(t) is 5, so why is strlen(s)-strlen(t)>c evaluating to true?

Answer 1

The strlen function returns a value of type size_t which is unsigned.

So subtracting unsigned 3 from unsigned 5 results in a very large unsigned number. This number is greater than 0 so the condition is true, causing strlen(s) to be evaluated and assigned to len.

The result of the subtraction should be cast to int to properly store a signed value.

int len=(((int)(strlen(s)-strlen(t))>c)?strlen(s):strlen(t));

Better yet, cast the result of each strlen to avoid an out-of-range conversion from unsigned to signed which is implementation defined:

int len= ((int)strlen(s)-(int)strlen(t))>c)?strlen(s):strlen(t);