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[libc++][hardening] Update documentation in the light of P3878. #166294

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[libc++][hardening] Update documentation in the light of P3878. #166294

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10 changes: 5 additions & 5 deletions libcxx/docs/Hardening.rst
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Original file line number Diff line number Diff line change
Expand Up @@ -305,11 +305,11 @@ Notes:
behavior; the ``observe`` semantic is meant to make adopting hardening easier
but should not be used outside of the adoption period;
- C++26 wording for Library Hardening precludes a conforming Hardened
implementation from using the Contracts ``ignore`` semantic when evaluating
hardened preconditions in the Library. Libc++ allows using this semantic for
hardened preconditions, but please be aware that using ``ignore`` does not
produce a conforming "Hardened" implementation, unlike the other semantics
above.
implementation from using a Contracts' non-terminating semantic (i.e.,
``ignore`` or ``observe``) when evaluating hardened preconditions in the
Library. Libc++ allows using these semantics for hardened preconditions, but
please be aware that using ``ignore`` or ``observe`` does not produce
a conforming "Hardened" implementation, unlike the terminating semantics above.
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@philnik777 philnik777 Nov 4, 2025

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Suggested change
a conforming "Hardened" implementation, unlike the terminating semantics above.
a "Hardened" implementation, unlike the terminating semantics above.

Would be better IMO - we're not a hardened implementation in these cases so there isn't much of a point in claiming "we're a non-conforming implementation", which makes it sound like we're just technically not.


The default assertion semantics are as follows:

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8 changes: 4 additions & 4 deletions libcxx/include/__config
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Expand Up @@ -193,10 +193,10 @@ _LIBCPP_HARDENING_MODE_DEBUG
// Notes:
// - Continuing execution after a hardening check fails results in undefined behavior; the `observe` semantic is meant
// to make adopting hardening easier but should not be used outside of this scenario;
// - C++26 wording for Library Hardening precludes a conforming Hardened implementation from using the Contracts
// `ignore` semantic when evaluating hardened preconditions in the Library. Libc++ allows using this semantic for
// hardened preconditions, however, be aware that using `ignore` does not produce a conforming "Hardened"
// implementation, unlike the other semantics above.
// - C++26 wording for Library Hardening precludes a conforming Hardened implementation from using a Contracts'
// non-terminating semantic (i.e., `ignore` or ``observe``) when evaluating hardened preconditions in the Library.
// Libc++ allows using these semantics for hardened preconditions, however, be aware that using `ignore` or `observe`
// does not produce a conforming "Hardened" implementation, unlike the terminating semantics above.
// clang-format off
# define _LIBCPP_ASSERTION_SEMANTIC_IGNORE (1 << 1)
# define _LIBCPP_ASSERTION_SEMANTIC_OBSERVE (1 << 2)
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