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190+ 最終更新日時(UTC):
191+ < span itemprop ="datePublished " content ="2025-07-07T13:40:35 ">
192+ 2025年07月07日 13時40分35秒
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198+ が更新
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207+ < span class ="fa fa-fw fa-pencil "> </ span > 編集
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214+
215+ < div class ="identifier-type "> function</ div > < div class ="header "> <cstdlib></ div > < h1 itemprop ="name "> < span class ="namespace " title ="namespace std "> std::</ span > < span class ="token "> free</ span > </ h1 >
216+ < div itemprop ="articleBody "> < p > < div class ="codehilite "> < pre > < span > </ span > < code > < span class ="k "> namespace</ span > < span class ="n "> std</ span > < span class ="p "> {</ span >
217+ < span class ="kt "> void</ span > < span class ="n "> free</ span > < span class ="p "> (</ span > < span class ="kt "> void</ span > < span class ="o "> *</ span > < span class ="n "> ptr</ span > < span class ="p "> )</ span > < span class ="k "> noexcept</ span > < span class ="p "> ;</ span >
218+ < span class ="p "> }</ span >
219+ </ code > </ pre > </ div >
220+ </ p >
221+ < h2 > 概要</ h2 >
222+ < p > < code > malloc</ code > 、< code > calloc</ code > 、< code > aligned_alloc</ code > 、< code > realloc</ code > で確保されたメモリ領域を解放する。</ p >
223+ < p > 解放済みのポインタを再度 < code > free</ code > に渡したり、アクセスしたりするときの< 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 "> 動作は未定義</ a > となる。</ p >
224+ < p > ポインタが< code > nullptr</ code > の場合、この関数は何も実行しない。</ p >
225+ < p > 解放されたポインタに再びアクセスする場合、< 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 > を引き起こす恐れがある。</ p >
226+ < h2 > 備考</ h2 >
227+ < p > この関数はスレッドセーフである。</ p >
228+ < h2 > 実装例</ h2 >
229+ < p > < div class ="yata " id ="de861629ea07af793bea02332b251fbfec19b586 "> < div class ="codehilite "> < pre > < span > </ span > < code > < span class ="kt "> int</ span > < span class ="nf "> main</ span > < span class ="p "> (</ span > < span class ="kt "> void</ span > < span class ="p "> )</ span >
230+ < span class ="p "> {</ span >
231+ < span class ="kt "> int</ span > < span class ="o "> *</ span > < span class ="n "> p1</ span > < span class ="o "> =</ span > < span class ="n "> malloc</ span > < span class ="p "> (</ span > < span class ="mi "> 10</ span > < span class ="o "> *</ span > < span class ="k "> sizeof</ span > < span class ="o "> *</ span > < span class ="n "> p1</ span > < span class ="p "> );</ span >
232+ < span class ="n "> free</ span > < span class ="p "> (</ span > < span class ="n "> p1</ span > < span class ="p "> );</ span > < span class ="c1 "> // p1のメモリを解放</ span >
233+
234+ < span class ="kt "> int</ span > < span class ="o "> *</ span > < span class ="n "> p2</ span > < span class ="o "> =</ span > < span class ="n "> calloc</ span > < span class ="p "> (</ span > < span class ="mi "> 10</ span > < span class ="p "> ,</ span > < span class ="k "> sizeof</ span > < span class ="o "> *</ span > < span class ="n "> p2</ span > < span class ="p "> );</ span >
235+ < span class ="kt "> int</ span > < span class ="o "> *</ span > < span class ="n "> p3</ span > < span class ="o "> =</ span > < span class ="n "> realloc</ span > < span class ="p "> (</ span > < span class ="n "> p2</ span > < span class ="p "> ,</ span > < span class ="mi "> 1000</ span > < span class ="o "> *</ span > < span class ="k "> sizeof</ span > < span class ="o "> *</ span > < span class ="n "> p3</ span > < span class ="p "> );</ span >
236+ < span class ="k "> if</ span > < span class ="p "> (</ span > < span class ="n "> p3</ span > < span class ="p "> )</ span >
237+ < span class ="n "> free</ span > < span class ="p "> (</ span > < span class ="n "> p3</ span > < span class ="p "> );</ span > < span class ="c1 "> // realloc により新しい領域が確保された場合、それを解放</ span >
238+ < span class ="k "> else</ span >
239+ < span class ="n "> free</ span > < span class ="p "> (</ span > < span class ="n "> p2</ span > < span class ="p "> );</ span > < span class ="c1 "> // realloc が失敗した場合は元の領域を解放</ span >
240+ < span class ="p "> }</ span >
241+ </ code > </ pre > </ div >
242+ </ div > </ p >
243+ < h3 > 出力</ h3 >
244+ < p > < pre > < code >
245+ </ code > </ pre > </ p >
246+ < h2 > 関連項目</ h2 >
247+ < ul >
248+ < li > < code > < a href ="aligned_alloc.html "> aligned_alloc</ a > </ code > :指定したアライメントでメモリを確保する</ li >
249+ < li > < code > < a href ="malloc.html "> malloc</ a > </ code > :メモリを確保する</ li >
250+ < li > < code > < a href ="calloc.html "> calloc</ a > </ code > :メモリを確保する(0で初期化する)</ li >
251+ < li > < code > < span href ="https://cpprefjp.github.io/reference/cstdlib/realloc.md.nolink "> realloc</ span > </ code > :メモリを再確保する</ li >
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