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cexpressionnumeric-limits

(~INT_MAX && INT_MAX) returns 1?

I am under the impression that INT_MAX will turn on all 32 bits of an int. If I negate that and 'and' it with itself, I should be comparing all 0s with all 1s and get back false. What am I missing?

int x = INT_MAX;
x = ~x && INT_MAX;
printf("x = %d\n", x); /*Returns 1*/
x = 0;
x = ~x && INT_MAX;
printf("x = %d\n", x); /*Returns 1*/

Edit: Oh wow I was flipping the sign bit as well. Using UNIT_MAX is giving me the result I needed. Thank you, everyone!

Solution

  • You're working with signed ints here; ~INT_MAX == INT_MIN (edit: for two's complement, which is what every modern processor uses), not 0. In C, all values except 0, including negatives, will evaluate to true when used in a conditional.

    If you switch to unsigned types everything should work as expected since ~UINT_MAX == 0.