tmp/tmpu7tzulft/{from.md → to.md}
RENAMED
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### Pointer safety <a id="util.dynamic.safety">[[util.dynamic.safety]]</a>
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A complete object is *declared reachable* while the number of calls to
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`declare_reachable` with an argument referencing the object exceeds the
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number of calls to `undeclare_reachable` with an argument referencing
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the object.
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``` cpp
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void declare_reachable(void* p);
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```
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*Preconditions:* `p` is a safely-derived
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pointer [[basic.stc.dynamic.safety]] or a null pointer value.
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*Effects:* If `p` is not null, the complete object referenced by `p` is
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subsequently declared reachable [[basic.stc.dynamic.safety]].
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*Throws:* May throw `bad_alloc` if the system cannot allocate additional
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memory that may be required to track objects declared reachable.
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``` cpp
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template<class T> T* undeclare_reachable(T* p);
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```
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*Preconditions:* If `p` is not null, the complete object referenced by
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`p` has been previously declared reachable, and is live [[basic.life]]
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from the time of the call until the last `undeclare_reachable(p)` call
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on the object.
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*Returns:* A safely derived copy of `p` which compares equal to `p`.
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*Throws:* Nothing.
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[*Note 1*: It is expected that calls to `declare_reachable(p)` will
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consume a small amount of memory in addition to that occupied by the
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referenced object until the matching call to `undeclare_reachable(p)` is
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encountered. Long running programs should arrange that calls are
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matched. — *end note*]
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``` cpp
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void declare_no_pointers(char* p, size_t n);
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```
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*Preconditions:* No bytes in the specified range are currently
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registered with `declare_no_pointers()`. If the specified range is in an
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allocated object, then it is entirely within a single allocated object.
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The object is live until the corresponding `undeclare_no_pointers()`
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call.
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[*Note 2*: In a garbage-collecting implementation, the fact that a
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region in an object is registered with `declare_no_pointers()` should
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not prevent the object from being collected. — *end note*]
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*Effects:* The `n` bytes starting at `p` no longer contain traceable
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pointer locations, independent of their type. Hence indirection through
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a pointer located there is undefined if the object it points to was
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created by global `operator new` and not previously declared reachable.
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[*Note 3*: This may be used to inform a garbage collector or leak
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detector that this region of memory need not be traced. — *end note*]
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*Throws:* Nothing.
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[*Note 4*: Under some conditions implementations may need to allocate
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memory. However, the request can be ignored if memory allocation
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fails. — *end note*]
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``` cpp
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void undeclare_no_pointers(char* p, size_t n);
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```
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*Preconditions:* The same range has previously been passed to
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`declare_no_pointers()`.
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*Effects:* Unregisters a range registered with `declare_no_pointers()`
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for destruction. It shall be called before the lifetime of the object
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ends.
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*Throws:* Nothing.
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``` cpp
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pointer_safety get_pointer_safety() noexcept;
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```
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*Returns:* `pointer_safety::strict` if the implementation has strict
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pointer safety [[basic.stc.dynamic.safety]]. It is
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*implementation-defined* whether `get_pointer_safety` returns
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`pointer_safety::relaxed` or `pointer_safety::preferred` if the
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implementation has relaxed pointer safety.[^1]
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