Library function strlen Source code reproduction and attention problems

First directly on the source:

size_t strlen (const char * str) {const char *eos = Str;while (*eos++); return (eos-str-1);}

You can see that the strlen is using a new char* pointer, which traverses backwards to find the next element in the end of the string. Then calculate the distance.

But notice here that a little size_t is actually unsigned int type. Therefore, you cannot use strlen (a)-strlen (b) when comparing the two string length size. Because two unsigned integer subtraction is not a negative number, the result is an integer regardless of how it is obtained. That is, strlen (a) is always greater than strlen (b).

You can use the expression strlen (a) > strlen (b) to determine the size of two strings, and you cannot use strlen (a)-strlen (b) > 0

Library function strlen Source code reproduction and attention problems