Sandra Loosemore <[email protected]> writes:
> On 10/6/25 19:03, Andrew Pinski wrote:
>> On Mon, Oct 6, 2025 at 5:58 PM Sam James <[email protected]> wrote:
>>>
>>> CCP interacts poorly with -Wuninitialized in some cases by assuming a value
>>> which stops us warning about it (false negatives). Inform users about this
>>> infamous interaction.
>>>
>>> gcc/ChangeLog:
>>> PR tree-optimization/18501
>>>
>>> * doc/invoke.texi (-Wuninitialized): Mention interaction with CCP.
>>> ---
>>> We give some 'more effective' notes like this for -ftree-vrp. What do you
>>> think?
>> Not a fan at all of the "more effective" here. Since unlike the other
>> effective notes which are about turning on optimizations, this is
>> about turning them off.
>> Maybe the following is better:
>> ```
>> -Wmaybe-uninitialized is known not to warn in many situations (false
>> negatives) due to some optimizations (like cpp, -ftree-ccp).
>> ```
>
> Yeah, my initial reaction was that "more effective" didn't really
> explain what the problem was. I think it would be better to phrase
> this more directly in the active voice, something like
I admit I chose somewhat "stub phrasing" because I wanted to see if
people were OK with the idea of "docs accommodating known, long-term
bugs" ;)
>
> Some optimizations interfere with @option{-Wmaybe-uninitialized} and
> may cause false negatives. In particular, disabling the conditional
> constant propagation pass with @option{-fno-tree-ccp} gives more
> accurate diagnostics.
I like that.
>
> ??
>
> -Sandra
