What is the output of the following script? Why? How can it be fixed to get the expected output?
#define __STDC_FORMAT_MACROS
#include <inttypes.h>
#include <stdio.h>
int main() {
uint64_t testvar;
testvar = 1<<30;
printf("2^30 = %" PRIu64 "\n", testvar);
testvar = 1<<31;
printf("2^31 = %" PRIu64 "\n", testvar);
return 0;
}
. . . . . . . . . . . . . . . . .
Answer
2^30 = 1073741824
2^31 = 18446744071562067968
Expected output
2^30 = 1073741824
2^31 = 2147483648
Explanation
1<<30 does a bitshift for int, not for uint64_t
How to fix it
Add a typecast:
#define __STDC_FORMAT_MACROS
#include <inttypes.h>
#include <stdio.h>
int main() {
uint64_t testvar;
testvar = 1<<30;
printf("2^30 = %" PRIu64 "\n", testvar);
testvar = ((uint64_t) 1)<<31;
printf("2^31 = %" PRIu64 "\n", testvar);
return 0;
}