Thread: Question with size_t and ssize_t

Originally Posted by Dante404

When I use the function printf() with a and b they seem to print the same number, but I don't understand why. To me, they seem to do the same thing as the int data type, but I think I'm missing something.

These kinds of claims are usually best made with some code to demonstrate what you tried and the output you received. For example, I compiled and ran:

Code:

#include <stdio.h>

int main(void)
{
    const ssize_t a = -1;
    const size_t b = (size_t) a;
    printf("ssize_t: %ld\nsize_t: %zu\n", a, b);
    return 0;
}

The output was:

Code:

ssize_t: -1
size_t: 18446744073709551615

which of course contradicts your claim that "they seem to print the same number".

Originally Posted by Dante404

Moreover, how does (size_t) affect the value of a in "size_t b = (size_t) a"?

It performs a cast, which is not absolutely necessary since there is an implicit conversion from signed integer types to unsigned integer types, but is still good to highlight that such a conversion is happening.

printf requires a format spec. Which did you use? The proper format for size_t is %zu. The proper one for ssize_t is %zd.
When you assign -1 to an unsigned value it's interpreted as the maximum value (kind of like starting an odometer at all 0's and turning it back one click).