[libc++] Apply post-commit review comments for unique_ptr<T[]> hardening (#111704)

[libc++] Correctly handle custom deleters in hardened unique_ptr<T[]> (#110685)

It turns out that we can never do bounds-checking for unique_ptrs with
custom deleters, except when converting from a

[libc++] Correctly handle custom deleters in hardened unique_ptr<T[]> (#110685)

It turns out that we can never do bounds-checking for unique_ptrs with
custom deleters, except when converting from a unique_ptr with a default
deleter to one with a custom deleter.

If we had an API like `std::make_unique` that allowed passing a custom
deleter, we could at least get bounds checking when the unique_ptr is
created through those APIs, but for now that is not possible.

Fixes #110683

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[libc++] Add an ABI setting to harden unique_ptr<T[]>::operator[] (#91798)

This allows catching OOB accesses inside `unique_ptr<T[]>` when the size
of the allocation is known. The size of the alloca

[libc++] Add an ABI setting to harden unique_ptr<T[]>::operator[] (#91798)

This allows catching OOB accesses inside `unique_ptr<T[]>` when the size
of the allocation is known. The size of the allocation can be known when
the unique_ptr has been created with make_unique & friends or when the
type necessitates an array cookie before the allocation.

This is a re-aplpication of 45a09d181 which had been reverted in
f11abac6 due to unrelated CI failures.

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[libc++] Add an ABI setting to harden unique_ptr<T[]>::operator[] (#91798)

This allows catching OOB accesses inside `unique_ptr<T[]>` when the size
of the allocation is known. The size of the alloc

[libc++] Add an ABI setting to harden unique_ptr<T[]>::operator[] (#91798)

This allows catching OOB accesses inside `unique_ptr<T[]>` when the size
of the allocation is known. The size of the allocation can be known when
the unique_ptr has been created with make_unique & friends or when the
type necessitates an array cookie before the allocation.

show more ...