CLion "Expression can be simplified" message on bitwise operation

Question

I was working on a C project and i wrote the following line to check if the most significant bit of an int8_t is 1:

if (f & 0b10000000 == 0b10000000) {

and CLion threw up a warning, telling me 'Expression can be simplified to "f != 0"'

Would I be right in saying this is incorrect? I read over bitwise operations to be sure and I still feel like these are not equivalent operations, for instance f = 1 would return false with my expression, but this message is making me doubt myself.

Thanks for any help you can give!

Answer 1

The bitwise "and" operator & has lower precedence than ==.

Therefore, your expression if (f & 0b10000000 == 0b10000000) is equivalent to if (f & (0b10000000 == 0b10000000)).

If you just want to test bit 7, try if (f & 0b10000000). Any non-zero value will be treated as "true".

Also, yes: CLion is wrong. Your original expression is equivalent to if (f & 1), which tests bit 0 (probably not what you intended).