回答編集履歴
2
refinement
answer
CHANGED
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@@ -10,6 +10,6 @@
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> An object pointer can be explicitly converted to an object pointer of a different type. 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))`. [...]
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----
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本題からはそれますが、変換先の型のアライメント要件によっては「未規定(unspecified)のポインタ値」（≠ 未定義(undefined)）となる可能性があります。[C++17 [static.cast]/13](https://timsong-cpp.github.io/cppwp/n4659/expr#static.cast-13)
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本題からはそれますが、変換先のオブジェクト型`T`のアライメント要件によっては「未規定(unspecified)のポインタ値」（≠ 未定義(undefined)）となる可能性があります。[C++17 [static.cast]/13](https://timsong-cpp.github.io/cppwp/n4659/expr#static.cast-13)
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> 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.
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1
appendix
answer
CHANGED
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@@ -7,4 +7,9 @@
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また、異なるオブジェクト型へのポインタ間の変換それ自体はwell-definedです。[C++17 [expr.reinterpret.cast]/p7](https://timsong-cpp.github.io/cppwp/n4659/expr.reinterpret.cast#7)
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> An object pointer can be explicitly converted to an object pointer of a different type. 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))`. [...]
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10
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> An object pointer can be explicitly converted to an object pointer of a different type. 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))`. [...]
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----
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13
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+
本題からはそれますが、変換先の型のアライメント要件によっては「未規定(unspecified)のポインタ値」（≠ 未定義(undefined)）となる可能性があります。[C++17 [static.cast]/13](https://timsong-cpp.github.io/cppwp/n4659/expr#static.cast-13)
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> 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.
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