pointer interconvertible

[yumetodo]

pointer interconvertible

[yumetodo]

異なるオブジェクト型へのポインタ間のキャストは以下で定義されています。https://t.co/QqzA00iyhI
ここで現れる static_cast について、結果の型の有効なオブジェクトを指すようになる条件が pointer-interconvertible を使って定められています。https://t.co/9O5hRHfjnt

— Kazutoshi SATODA (@k-satoda) November 29, 2020

https://timsong-cpp.github.io/cppwp/n4861/expr.reinterpret.cast#7

An object pointer can be explicitly converted to an object pointer of a different type.⁶⁴
When a prvalue v of object pointer type is converted to the object pointer type “pointer to cv T”, the result is static_­cast<cv T*>(static_­cast<cv void*>(v)).
[ Note: Converting a prvalue of type “pointer to T1” to the type “pointer to T2” (where T1 and T2 are object types and where the alignment requirements of T2 are no stricter than those of T1) and back to its original type yields the original pointer value.
— end note
]

64. The types may have different cv-qualifiers, subject to the overall restriction that a reinterpret_­cast cannot cast away constness. ⮥

https://timsong-cpp.github.io/cppwp/n4861/expr.static.cast#13

A prvalue of type “pointer to cv1 void” can be converted to a prvalue of type “pointer to cv2 T”, where T is an object type and cv2 is the same cv-qualification as, or greater cv-qualification than, cv1.
If the original pointer value represents the address A of a byte in memory and A does not satisfy the alignment requirement of T, then the resulting pointer value is unspecified.
Otherwise, if the original pointer value points to an object a, and there is an object b of type T (ignoring cv-qualification) that is pointer-interconvertible with a, the result is a pointer to b.
Otherwise, the pointer value is unchanged by the conversion.
[ Example:

T* p1 = new T;
const T* p2 = static_cast<const T*>(static_cast<void*>(p1));
bool b = p1 == p2;  // b will have the value true.

— end example
]