tmp/tmptqamvkid/{from.md → to.md}
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#### Safely-derived pointers <a id="basic.stc.dynamic.safety">[[basic.stc.dynamic.safety]]</a>
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A *traceable pointer object* is
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- an object of an object pointer type
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- an object of an integral type that is at least as large as
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`std::intptr_t`, or
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- a sequence of elements in an array of narrow character type
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[[basic.fundamental]]
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match those of some object pointer type.
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A pointer value is a *safely-derived pointer* to
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- the value returned by a call to the C++standard library
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of `::operator new(std::{}size_t)` or
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`::operator new(std::size_t, std::align_val_t)` ;[^
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- the result of taking the address of an object (or one of its
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subobjects) designated by an lvalue resulting from indirection through
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a safely-derived pointer value;
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- the result of well-defined pointer arithmetic
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safely-derived pointer value;
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- the result of a well-defined pointer conversion ([[conv.ptr]],
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[[expr.cast]]) of a safely-derived pointer value;
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- the result of a `reinterpret_cast` of a safely-derived pointer value;
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- the result of a `reinterpret_cast` of an integer representation of a
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safely-derived pointer value;
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- the value of an object whose value was copied from a traceable pointer
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object, where at the time of the copy the source object contained a
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@@ -49,17 +51,15 @@ An implementation may have *relaxed pointer safety*, in which case the
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validity of a pointer value does not depend on whether it is a
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safely-derived pointer value. Alternatively, an implementation may have
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*strict pointer safety*, in which case a pointer value referring to an
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object with dynamic storage duration that is not a safely-derived
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pointer value is an invalid pointer value unless the referenced complete
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object has previously been declared reachable
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[[util.dynamic.safety]]).
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[*Note
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passing it to a deallocation function) is undefined, see
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safely-derived pointer value. — *end note*]
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It is *implementation-defined* whether an implementation has relaxed or
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strict pointer safety.
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##### Safely-derived pointers <a id="basic.stc.dynamic.safety">[[basic.stc.dynamic.safety]]</a>
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A *traceable pointer object* is
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- an object of an object pointer type [[basic.compound]], or
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- an object of an integral type that is at least as large as
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`std::intptr_t`, or
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- a sequence of elements in an array of narrow character type
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[[basic.fundamental]], where the size and alignment of the sequence
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match those of some object pointer type.
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A pointer value is a *safely-derived pointer* to an object with dynamic
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storage duration only if the pointer value has an object pointer type
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and is one of the following:
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- the value returned by a call to the C++ standard library
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implementation of `::operator new(std::{}size_t)` or
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`::operator new(std::size_t, std::align_val_t)` ;[^16]
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- the result of taking the address of an object (or one of its
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subobjects) designated by an lvalue resulting from indirection through
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a safely-derived pointer value;
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- the result of well-defined pointer arithmetic [[expr.add]] using a
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safely-derived pointer value;
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- the result of a well-defined pointer conversion ([[conv.ptr]],
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[[expr.type.conv]], [[expr.static.cast]], [[expr.cast]]) of a
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safely-derived pointer value;
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- the result of a `reinterpret_cast` of a safely-derived pointer value;
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- the result of a `reinterpret_cast` of an integer representation of a
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safely-derived pointer value;
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- the value of an object whose value was copied from a traceable pointer
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object, where at the time of the copy the source object contained a
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validity of a pointer value does not depend on whether it is a
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safely-derived pointer value. Alternatively, an implementation may have
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*strict pointer safety*, in which case a pointer value referring to an
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object with dynamic storage duration that is not a safely-derived
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pointer value is an invalid pointer value unless the referenced complete
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object has previously been declared reachable [[util.dynamic.safety]].
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[*Note 6*: The effect of using an invalid pointer value (including
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passing it to a deallocation function) is undefined, see [[basic.stc]].
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This is true even if the unsafely-derived pointer value might compare
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equal to some safely-derived pointer value. — *end note*]
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It is *implementation-defined* whether an implementation has relaxed or
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strict pointer safety.
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