They are comparable because they both address the needs of Functional
Safety as per p3578 <http://wg21.link/p3578>. SG23 took a poll on whether
they're better than macros see P3297 <http://wg21.link/P3297>.

I think it's not a leap of logic that EWG has strong consensus to pass
P2900 precisely because they feel it's strictly better than macros.

Cheers,

On Mon, Oct 20, 2025 at 12:58 PM John Spicer <jhs_at_[hidden]> wrote:

> We have never taken a poll of whether P2900 is better then macro solutions.
>
> Could you explain why you think contracts and macro-based solutions are
> comperable?
>
> John.
>
> On Oct 20, 2025, at 3:09 PM, Ryan McDougall <mcdougall.ryan_at_[hidden]>
> wrote:
>
> I’m saying we have decades of experience with macro based systems, which
> defines the floor of features/expectations. The consensus is P2900 is
> better taken as a whole. There are things i think should be different with
> p2900, but p2900 represents consensus. There has been no evidence put
> forward that there is a more correct course. Based on those decades of
> experience here are no outstanding questions that having a TS would answer.
>
> If i am wrong, please list precise questions that a TS would answer. “We
> don’t have enough experience” is a statement.
>
> Cheers,
>
> On Mon, Oct 20, 2025 at 11:54 AM John Spicer <jhs_at_[hidden]> wrote:
>
>> You keep saying things like we have “decades of experience with
>> macro-based systems”.
>>
>> If contracts were remotely similar to macro-based systems, we would not
>> be having this discussion.
>>
>> The problem is that contracts are *vastly* different.
>>
>> If you put P2900 and macro-based systems in the same set, that means you
>> don’t understand one or the other.
>>
>> John.
>>
>> On Oct 20, 2025, at 2:22 PM, Ryan McDougall via SG21 <
>> sg21_at_[hidden]> wrote:
>>
>> The "course corrections" do not actually suggest a future course (beyond
>> asserting without evidence"we need more experience" and kicking the can
>> down the road to a TS) -- we've had years for alternative proposals to be
>> put forward, and none have surpassed P2900.
>>
>> We *do* have decades of experience with macro-based systems, we *do* have
>> decades of experience building software at scale (see Software
>> Engineering at Google <https://abseil.io/resources/swe-book>), and we
>> *do* know who our users are (see P1995 and P3297) -- and while there are
>> many variations on contracts, P2900 represents our best consensus
>> interpretation of those decades of experience. Not all of these decisions
>> were everyone's first choice, but P2900 is the consensus. There is no
>> evidence that any other option would improve that.
>>
>> Multiple papers, like P2900 and P3578 <http://wg21.link/p3578> explain
>> exactly who the feature is for, and how and why each of these design
>> choices were made. There is no reason to believe the current course is
>> incorrect, or that another course would be more correct.
>>
>> On Mon, Oct 20, 2025 at 4:58 AM Ville Voutilainen via SG21 <
>> sg21_at_[hidden]> wrote:
>>
>>> On Mon, 20 Oct 2025 at 14:34, Timur Doumler via SG15
>>> <sg15_at_[hidden]> wrote:
>>> > Given the above, it seems to me like opposing C++26 contract
>>> assertions because you want that checks are always on / always enforced is
>>> kinda like this:
>>> >
>>> > – Alice: "I want safer roads for pedestrians." (reasonable and good
>>> request)
>>> > – Bob: "Here's a proposal to fund bike lanes in the city." (reasonable
>>> and good proposal roughly in the same area but with a different goal)
>>> > – Alice: "But bike lanes don't add more crosswalks or reduce speed
>>> limits. So they don't make roads safer for pedestrians. Therefore, we
>>> should not build bike lanes."
>>> >
>>> > Here, Alice is committing a logical fallacy. Just because bike lanes
>>> are not useful for Alice, it doesn't mean that they're not useful for Bob,
>>> and taking away bike lanes from Bob does nothing to give Alice what she
>>> wants.
>>>
>>> The colorful analogy doesn't include considerations where providing
>>> bike lanes for Bob and doing nothing else is not entirely harmless for
>>> the pedestrians Alice is focused on.
>>>
>>> It's also incorrect in its suggestion that bike lanes are not useful
>>> for Alice. Nobody has said that P2900 isn't useful. That's why it's
>>> included
>>> in *every* *single* *one* of the currently active proposals suggesting
>>> course corrections.
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>>>
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>>
>>
>>
>