[out.ptr.t][inout.ptr.t] Get rid of TBAA-violating implication #8740
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On many platforms, we can just reuse the object/value representation of the raw pointer stored within `(in)out_ptr_t` for `operator void**`. However, directly use of `reinterpret_cast` violates the strict aliasing rule ([basic.lval]/11). At the time when `out_ptr_t` and `inout_ptr_t` were added to C++23, there was not yet any standard utility bypassing the strict aliasing rule, and thus the notes had to indicate core UB and were only applicable for implementations that didn't aggressively perform type-based aliasing analysis (TBAA). Luckily, `start_lifetime_as` was added later, making it possible to reuse value representation without UB. This PR uses `start_lifetime_as` in the notes, and thus makes them probably applicable for implementations that have compatible representations for `T*` and `void*`. Note that `start_lifetime_as` can cause conflicts on object creation, but conflicts are already allowed in [out.ptr.t]/5 and [inout.ptr.t]/5.
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On many platforms, we can just reuse the object/value representation of the raw pointer stored within
(in)out_ptr_tforoperator void**. However, directly use ofreinterpret_castviolates the strict aliasing rule ([basic.lval]/11). At the time whenout_ptr_tandinout_ptr_twere added to C++23, there was not yet any standard utility bypassing the strict aliasing rule, and thus the notes had to indicate core UB and were only applicable for implementations that didn't aggressively perform type-based aliasing analysis (TBAA).Luckily,
start_lifetime_aswas added later, making it possible to reuse value representation without UB. This PR usesstart_lifetime_asin the notes, and thus makes them probably applicable for implementations that have compatible representations forT*andvoid*.Note that
start_lifetime_ascan cause conflicts on object creation, but conflicts are already allowed in [out.ptr.t]/5 and [inout.ptr.t]/5.