Date: Wed, 15 Oct 2025 03:48:02 +0000
[Tom]
*
If you mean that libc++ isn't specifically calling the C++26 contract violation handler, I agree.
We are in violent agreement - assuming we are both trying to refer to facts teetered to reality.
-- Gaby
________________________________
From: Tom Honermann <tom_at_[hidden]>
Sent: Tuesday, October 14, 2025 4:43:09 PM
To: sg21_at_[hidden] <sg21_at_[hidden]>; sg15_at_[hidden] <sg15_at_[hidden]>
Cc: Gabriel Dos Reis <gdr_at_[hidden]>
Subject: Re: [isocpp-sg21] [isocpp-sg15] P3835 -- Different contract checking for different libraries
On 10/14/25 4:35 PM, Gabriel Dos Reis via SG21 wrote:
The existing practice doesn't demonstrate any of that.
I'm afraid I don't know precisely what you are referring to by "any of that".
If you mean that libc++ isn't specifically calling the C++26 contract violation handler, I agree. But I can clearly see that a change to do so would involve a trivial change to the libc++ source code.
Tom.
-- Gaby
________________________________
From: Tom Honermann <tom_at_[hidden]><mailto:tom_at_[hidden]>
Sent: Tuesday, October 14, 2025 4:32:42 PM
To: sg21_at_[hidden]<mailto:sg21_at_[hidden]> <sg21_at_[hidden]><mailto:sg21_at_[hidden]>; sg15_at_[hidden]<mailto:sg15_at_[hidden]> <sg15_at_[hidden]><mailto:sg15_at_[hidden]>
Cc: Gabriel Dos Reis <gdr_at_[hidden]><mailto:gdr_at_[hidden]>
Subject: Re: [isocpp-sg21] [isocpp-sg15] P3835 -- Different contract checking for different libraries
On 10/14/25 4:17 PM, Gabriel Dos Reis via SG21 wrote:
[Tom]
* They are, or will be, once either of P3290 (Integrating Existing Assertions With Contracts)<https://wg21.link/p3290> or P3400 (Specifying Contract Assertion Properties with Labels)<https://wg21.link/p3400> is adopted.
If that conjecture is true, then I would recommend to wait for those papers to be implemented, with deployment experience and adopted before phrasing the hardened standard library in terms of contracts.
I find the existing practice as demonstrated by libc++ both sufficient and compelling. I accept that you may feel differently.
Tom.
-- Gaby
From: SG15 <sg15-bounces_at_[hidden]><mailto:sg15-bounces_at_[hidden]> On Behalf Of Tom Honermann via SG15
Sent: Tuesday, October 14, 2025 4:00 PM
To: sg21_at_[hidden]<mailto:sg21_at_[hidden]>; Ville Voutilainen via SG15 <sg15_at_[hidden]><mailto:sg15_at_[hidden]>
Cc: Tom Honermann <tom_at_[hidden]><mailto:tom_at_[hidden]>
Subject: Re: [isocpp-sg15] [isocpp-sg21] P3835 -- Different contract checking for different libraries
On 10/14/25 3:21 PM, Ran Regev via SG21 wrote:
On Tue, Oct 14, 2025, 21:47 Ville Voutilainen via SG15 <sg15_at_[hidden]<mailto:sg15_at_[hidden]>> wrote:
On Tue, 14 Oct 2025 at 21:42, Ryan McDougall <mcdougall.ryan_at_[hidden]<mailto:mcdougall.ryan_at_[hidden]>> wrote:
>
> And there are existing deployments where it's not desired and not a requirement...
That doesn't mean that hardening should be possible to be turned off
by a contract evaluation semantic choice
One of the fundamental aspects of p2900 is that the person who write the contract is not the one who selects the semantics for the application.
Is this aspect of contracts aligned with hardened libraries needs? The discussion seems to reveal that not. And therefore the draft paper mentioned earlier seems to be correct - contracts are not good fit for standard library hardening.
They are, or will be, once either of P3290 (Integrating Existing Assertions With Contracts)<https://wg21.link/p3290> or P3400 (Specifying Contract Assertion Properties with Labels)<https://wg21.link/p3400> is adopted.
Tom.
applying to other code. Or more in the opposite direction, it doesn't
mean that the choice of a contract evaluation semantic
for other code should turn the hardening off.
> The original sin is thinking that any one engineer knows all domains and anything that doesn't fit their preconceptions is universally wrong.
Funny, you seem to be the only person in this discussion stating that
something is universally wrong, or otherwise I have misunderstood
what you think "patently false" means.
>P2900 has been in development for a long time, and is useful and needed. The idea it's "unsafe" shows a lack of understanding of what that word means.
Oh sure, it's a likely story that the critics of P2900 simply
misunderstand something. In fact, a story so unlikely that it's safe
to say it's patently false.
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*
If you mean that libc++ isn't specifically calling the C++26 contract violation handler, I agree.
We are in violent agreement - assuming we are both trying to refer to facts teetered to reality.
-- Gaby
________________________________
From: Tom Honermann <tom_at_[hidden]>
Sent: Tuesday, October 14, 2025 4:43:09 PM
To: sg21_at_[hidden] <sg21_at_[hidden]>; sg15_at_[hidden] <sg15_at_[hidden]>
Cc: Gabriel Dos Reis <gdr_at_[hidden]>
Subject: Re: [isocpp-sg21] [isocpp-sg15] P3835 -- Different contract checking for different libraries
On 10/14/25 4:35 PM, Gabriel Dos Reis via SG21 wrote:
The existing practice doesn't demonstrate any of that.
I'm afraid I don't know precisely what you are referring to by "any of that".
If you mean that libc++ isn't specifically calling the C++26 contract violation handler, I agree. But I can clearly see that a change to do so would involve a trivial change to the libc++ source code.
Tom.
-- Gaby
________________________________
From: Tom Honermann <tom_at_[hidden]><mailto:tom_at_[hidden]>
Sent: Tuesday, October 14, 2025 4:32:42 PM
To: sg21_at_[hidden]<mailto:sg21_at_[hidden]> <sg21_at_[hidden]><mailto:sg21_at_[hidden]>; sg15_at_[hidden]<mailto:sg15_at_[hidden]> <sg15_at_[hidden]><mailto:sg15_at_[hidden]>
Cc: Gabriel Dos Reis <gdr_at_[hidden]><mailto:gdr_at_[hidden]>
Subject: Re: [isocpp-sg21] [isocpp-sg15] P3835 -- Different contract checking for different libraries
On 10/14/25 4:17 PM, Gabriel Dos Reis via SG21 wrote:
[Tom]
* They are, or will be, once either of P3290 (Integrating Existing Assertions With Contracts)<https://wg21.link/p3290> or P3400 (Specifying Contract Assertion Properties with Labels)<https://wg21.link/p3400> is adopted.
If that conjecture is true, then I would recommend to wait for those papers to be implemented, with deployment experience and adopted before phrasing the hardened standard library in terms of contracts.
I find the existing practice as demonstrated by libc++ both sufficient and compelling. I accept that you may feel differently.
Tom.
-- Gaby
From: SG15 <sg15-bounces_at_[hidden]><mailto:sg15-bounces_at_[hidden]> On Behalf Of Tom Honermann via SG15
Sent: Tuesday, October 14, 2025 4:00 PM
To: sg21_at_[hidden]<mailto:sg21_at_[hidden]>; Ville Voutilainen via SG15 <sg15_at_[hidden]><mailto:sg15_at_[hidden]>
Cc: Tom Honermann <tom_at_[hidden]><mailto:tom_at_[hidden]>
Subject: Re: [isocpp-sg15] [isocpp-sg21] P3835 -- Different contract checking for different libraries
On 10/14/25 3:21 PM, Ran Regev via SG21 wrote:
On Tue, Oct 14, 2025, 21:47 Ville Voutilainen via SG15 <sg15_at_[hidden]<mailto:sg15_at_[hidden]>> wrote:
On Tue, 14 Oct 2025 at 21:42, Ryan McDougall <mcdougall.ryan_at_[hidden]<mailto:mcdougall.ryan_at_[hidden]>> wrote:
>
> And there are existing deployments where it's not desired and not a requirement...
That doesn't mean that hardening should be possible to be turned off
by a contract evaluation semantic choice
One of the fundamental aspects of p2900 is that the person who write the contract is not the one who selects the semantics for the application.
Is this aspect of contracts aligned with hardened libraries needs? The discussion seems to reveal that not. And therefore the draft paper mentioned earlier seems to be correct - contracts are not good fit for standard library hardening.
They are, or will be, once either of P3290 (Integrating Existing Assertions With Contracts)<https://wg21.link/p3290> or P3400 (Specifying Contract Assertion Properties with Labels)<https://wg21.link/p3400> is adopted.
Tom.
applying to other code. Or more in the opposite direction, it doesn't
mean that the choice of a contract evaluation semantic
for other code should turn the hardening off.
> The original sin is thinking that any one engineer knows all domains and anything that doesn't fit their preconceptions is universally wrong.
Funny, you seem to be the only person in this discussion stating that
something is universally wrong, or otherwise I have misunderstood
what you think "patently false" means.
>P2900 has been in development for a long time, and is useful and needed. The idea it's "unsafe" shows a lack of understanding of what that word means.
Oh sure, it's a likely story that the critics of P2900 simply
misunderstand something. In fact, a story so unlikely that it's safe
to say it's patently false.
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Received on 2025-10-15 03:48:12