Remove misleading XOR

[Timm Bäder]

On 24/02/2021 14:16, Mark Wielaard wrote:
> Hmmm. I am not sure why that doesn't work. What if you make them
> explicitly unsinged (adding u at the end). Or does it simply ignore
> the values and just warn because it sees the macro name and not an
> explicit number?
> 
> I think I don't really understand anymore what this warning is warning
> about.  Could you give an example of where this would flag something
> that we would like to fix?

I found https://gcc.gnu.org/bugzilla/show_bug.cgi?id=90885, which has a
few more use-cases (in the form of tweets but anyway). GCC might also
get this warning in the future.

For the clang implementation, see https://reviews.llvm.org/D63423

So it only seems to warn for 2 ^ x because that's a common error:

#define NO_RESIZING 0x0u
#define CLEANING    0x2u
int main(void) {
   unsigned p = CLEANING ^ NO_RESIZING;
   unsigned j = NO_RESIZING ^ CLEANING;
   unsigned k = 17 ^ 3;
}

This code only warns for the declaration of p.


> Maybe it is easiest to just suppress this warning, when is it enabled?

That's fine with me, I just didn't want to add compiler-specific flags
but I guess we can just check for -Wno-xor-used-as-pow and add that when
the compiler supports it.



- Timm

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