Question

It’s my understanding that uint64_t defined by C99 (stdint.h) is defined to be 8 bytes (= 64 bits) of length, thus allowing for a maximum value of 2^64 – 1. However, when I try the following code snippet, the uint64_t overflows, even though it’s nowhere near 2^64 – 1:

uint64_t Power10(int exponent)
{
    int i = 1;
    uint64_t ret = 10;
    while(i < exponent)
    {
        ret *= 10;
        ++i;
    }

    return ret;
}

Help would be very much appreciated.

Answer 1

You need to print with "%" PRIu64 conversion. Don’t forget to add the right include!

#include <inttypes.h>
int main(void) {
    printf("Power10(12) is %" PRIu64 "\n", Power10(12));
    return 0;
}