On Sat, Nov 9, 2024, 11:19 AM Sad Clouds via Gcc <gcc@gcc.gnu.org> wrote:
> Hello, I don't know if this is a known GCC bug or intentional design,
> but code like this:
>
> double value = 0.0;
> ...
> if (value == 0.0)
> {
> ...
> }
>
> Results in the following warning with gcc-12.2.0:
>
> "... warning: comparing floating-point with ‘==’ or ‘!=’ is unsafe"
>
> Even though there is nothing unsafe here and comparison to floating
> point 0.0 value is well defined.
>
> The LLVM clang seems to handle this correctly and does not produce any
> warnings with -Wfloat-equal option.
>
> Is there any way to silence GCC without disabling -Wfloat-equal?
>
You can use the diagnostic pragma to disable it directly for the statement.
But I will note comparing double even against 0 can be problematic. You
might not get exactly 0 in some cases with things like FMA or when using
x87 instructions set.
That is it still unsafe. Why clang does not warn is for them to answer.
> Thanks.
>
