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174+ < span itemprop ="name "> 不完全型へのポインタに対するdeleteを不適格とする [P3144R2]</ span >
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190+ 最終更新日時(UTC):
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192+ 2025年04月25日 08時13分12秒
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196+ < span itemprop ="name "> Akira Takahashi</ span >
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198+ が更新
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215+ < h1 itemprop ="name "> < span class ="token "> 不完全型へのポインタに対するdeleteを不適格とする [P3144R2]</ span > < span class ="cpp cpp26 " title ="C++26で追加 "> (C++26)</ span > </ h1 >
216+ < div itemprop ="articleBody "> < p > </ p >
217+ < p > このページはC++26に採用される見込みの言語機能の変更を解説しています。</ p >
218+ < p > のちのC++規格でさらに変更される場合があるため関連項目を参照してください。</ p >
219+ < p > </ p >
220+ < h2 > 概要</ h2 >
221+ < p > 宣言のみで定義がない< a class ="cpprefjp-defined-word " data-desc ="型のサイズを決定できない、完全には定義されていない型。例えば先行宣言のみのクラス型、要素数不明の配列型、`void`など。クラス定義内部ではそのクラス自身は不完全型 "> 不完全型</ a > へのポインタへの< code > delete</ code > は、これまで< a class ="cpprefjp-defined-word " data-desc ="未定義の動作。処理系は予期せぬ動作をする可能性がある。要するに動作保証対象外。undefined behavior (UB)。 " href ="../../implementation-compliance.html#dfn-undefined-behavior "> 未定義動作</ a > を引き起こす操作になっていた。</ p >
222+ < p > C++26ではこれを< a class ="cpprefjp-defined-word " data-desc ="プログラムが適格でないこと。コンパイルエラーなどになる " href ="../../implementation-compliance.html#dfn-ill-formed "> 不適格</ a > とし、コンパイル時エラーとする。</ p >
223+ < p > < div class ="codehilite "> < pre > < span > </ span > < code > < span class ="k "> class</ span > < span class ="nc "> C</ span > < span class ="p "> ;</ span > < span class ="c1 "> // 不完全型の宣言</ span >
224+ < span class ="n "> C</ span > < span class ="o "> *</ span > < span class ="n "> cp</ span > < span class ="o "> =</ span > < span class ="k "> nullptr</ span > < span class ="p "> ;</ span > < span class ="c1 "> // 不完全型へのポインタはOK</ span >
225+ < span class ="k "> delete</ span > < span class ="n "> cp</ span > < span class ="p "> ;</ span > < span class ="c1 "> // C++23:未定義動作, C++26:コンパイルエラー</ span >
226+ </ code > </ pre > </ div >
227+ </ p >
228+ < h2 > 参照</ h2 >
229+ < ul >
230+ < li > < a href ="https://open-std.org/jtc1/sc22/wg21/docs/papers/2024/p3144r2.pdf " target ="_blank "> P3144R2 Deleting a Pointer to an Incomplete Type Should be Ill-formed</ a > </ li >
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