Re: What is your opinion about unsigned int u = -2 ?

On 11/08/2024 21:53, James Kuyper wrote:

On 8/11/24 16:08, Vir Campestris wrote:
...

"Converting -1 to an unsigned type always sets all the bits"
>
In any normal twos complement architecture that's the case. But there
are a few oddballs out there where -1 is +1, except that the dedicated
sign bit is set.

 There may be hardware where that is true, but a conforming
implementation of C targeting that hardware cannot use the hardware's
result. It must fix up the result produced by the hardware to match the
result required by the C standard.
 

On 11/08/2024 21:45, Richard Damon wrote:
 >
 > But, when that -1 value is converted to an unsigned type, that VALUE
 > will be adjusted modulo the appropriate power of two.
 >
 > signed to unsigned conversion works on VALUE, not bit pattern, so is
 > invariant with the representation of the negative values.
 >
 > Yes, in a union with a signed and unsigned, the type punning will let
 > you see the representation of the types, but assignment works on values.
Ah, thank you both. It's academic interest only of course!
Andy