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174+ < span itemprop ="name "> 文字列リテラルの文字エンコーディング失敗を不適格とする [P1854R4]</ span >
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190+ 最終更新日時(UTC):
191+ < span itemprop ="datePublished " content ="2025-04-04T07:20:26 ">
192+ 2025年04月04日 07時20分26秒
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195+ < span itemprop ="author " itemscope itemtype ="http://schema.org/Person ">
196+ < span itemprop ="name "> Akira Takahashi</ span >
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198+ が更新
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200+
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204+ < span class ="fa fa-fw fa-clock-o fa-flip-horizontal "> </ span > 履歴
205+ </ a >
206+ < a class ="edit " target ="_blank " href ="https://github.com/cpprefjp/site/edit/master/lang/cpp26/making_non-encodable_string_literals_ill-formed.md ">
207+ < span class ="fa fa-fw fa-pencil "> </ span > 編集
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214+
215+ < h1 itemprop ="name "> < span class ="token "> 文字列リテラルの文字エンコーディング失敗を不適格とする [P1854R4]</ 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< a href ="#relative-page "> 関連項目</ a > を参照してください。</ p >
219+ < p > </ p >
220+ < h2 > 概要</ h2 >
221+ < p > C++23では、以下のような1ワイド文字に収まらないリテラルが< 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 > (コンパイルエラー) になるよう仕様変更された。</ p >
222+ < p > < div class ="codehilite "> < pre > < span > </ span > < code > < span class ="kt "> wchar_t</ span > < span class ="n "> a</ span > < span class ="o "> =</ span > < span class ="sa "> L</ span > < span class ="sc "> '🤦'</ span > < span class ="p "> ;</ span > < span class ="c1 "> // C++20:OK, C++23:OK \U0001f926</ span >
223+ < span class ="kt "> wchar_t</ span > < span class ="n "> b</ span > < span class ="o "> =</ span > < span class ="n "> L</ span > < span class ="err "> '</ span > < span class ="n "> ab</ span > < span class ="err "> '</ span > < span class ="p "> ;</ span > < span class ="c1 "> // C++20:OK, C++23:NG マルチキャラクタリテラル</ span >
224+ < span class ="kt "> wchar_t</ span > < span class ="n "> c</ span > < span class ="o "> =</ span > < span class ="n "> L</ span > < span class ="err "> '</ span > < span class ="n "> e</ span > < span class ="err "> ́'</ span > < span class ="p "> ;</ span > < span class ="c1 "> // C++20:OK, C++23:NG \u0065\u0301</ span >
225+ </ code > </ pre > </ div >
226+ </ p >
227+ < p > C++26ではさらに、文字列リテラルとしてエンコーディングできない文字の扱いが< a class ="cpprefjp-defined-word " data-desc ="処理系定義の動作。処理系によって事前に定めた動作をする " href ="../../implementation-compliance.html#dfn-implementation-defined-behavior "> 実装定義</ a > でコンパイラーに任されていたものを、< 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 > になるよう仕様変更する。</ p >
228+ < p > < div class ="codehilite "> < pre > < span > </ span > < code > < span class ="kt "> wchar_t</ span > < span class ="n "> ao</ span > < span class ="o "> =</ span > < span class ="n "> L</ span > < span class ="err "> '\</ span > < span class ="n "> x123456789abcdef0</ span > < span class ="err "> '</ span > < span class ="p "> ;</ span > < span class ="c1 "> // C++23:実装定義, C++26:NG (範囲外)</ span >
229+ < span class ="kt "> char16_t</ span > < span class ="n "> ap</ span > < span class ="o "> =</ span > < span class ="n "> u</ span > < span class ="err "> '\</ span > < span class ="n "> x12345678</ span > < span class ="err "> '</ span > < span class ="p "> ;</ span > < span class ="c1 "> // C++23:実装定義, C++26:NG (範囲外)</ span >
230+ </ code > </ pre > </ div >
231+ </ p >
232+ < p > また、マルチ文字リテラル (ひとつの文字リテラルに4文字まで入れられて値が< a class ="cpprefjp-defined-word " data-desc ="処理系定義の動作。処理系によって事前に定めた動作をする " href ="../../implementation-compliance.html#dfn-implementation-defined-behavior "> 実装定義</ a > なもの。例として< code > 'intl'</ code > ) については、単一のコードユニットにエンコードされるもののみ許可される。</ p >
233+ < h2 > 関連項目</ h2 >
234+ < ul >
235+ < li > < a href ="../cpp23/remove_non_encodable_wide_character_literals_and_multicharacter_wide_character_literals.html "> C++23 1ワイド文字に収まらないワイド文字リテラルを禁止する</ a > </ li >
236+ </ ul >
237+ < h2 > 参照</ h2 >
238+ < ul >
239+ < li > < a href ="http://open-std.org/jtc1/sc22/wg21/docs/papers/2023/p1854r4.pdf " target ="_blank "> P1854R4 Making non-encodable string literals ill-formed</ a > </ li >
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