What return type do sizeof() have?

Question

#include <stdio.h>
int main() {
printf("float: %ld \n", sizeof(float));
printf("double: %lu \n", sizeof(double));
printf("char: %ld \n", sizeof(char));
return 0;
}

//why is sizeof return type working with both %lu and %ld format specifier

Answer 1

Naively speaking, it is illogical to try to represent size measurement by using negative number. So size measurement fits the characteristics of unsigned integer family.

You *probably* may find incorrect or unexpected result when using signed integer %ld specifier when the size of the object to analyse (by sizeof) surpass the maximum value of signed integer data range.