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<header data-kunai-mdinfo="{"meta": {"header": ["memory"], "namespace": ["std"], "class": ["shared_ptr"], "id-type": ["function"], "cpp": ["cpp11"]}, "sources": [{"id": "2c065dc109ebb79554cf786f320995e7069d65ba", "source": "#include <cassert>\n#include <memory>\n#include <utility>\n\nstruct X {\n int i;\n\n X(int i = 0)\n : i(i) {}\n};\n\nint main()\n{\n // (1)\n // \u30c7\u30d5\u30a9\u30eb\u30c8\u69cb\u7bc9\u3002\n // \u7a7a\u306eshared_ptr\u30aa\u30d6\u30b8\u30a7\u30af\u30c8\u3092\u69cb\u7bc9\u3059\u308b\n std::shared_ptr<int> p1;\n assert(p1.get() == nullptr);\n assert(p1.use_count() == 0);\n\n // (2)\n // \u30dd\u30a4\u30f3\u30bf\u306e\u6240\u6709\u6a29\u3092\u53d7\u3051\u53d6\u308b\u3002\n std::shared_ptr<int> p2(new int(3));\n assert(*p2.get() == 3);\n assert(p2.use_count() == 1);\n\n // (3)\n // \u30dd\u30a4\u30f3\u30bf\u306e\u6240\u6709\u6a29\u3068\u3001\u30c7\u30ea\u30fc\u30bf\u3092\u53d7\u3051\u53d6\u308b\u3002\n // \u30ea\u30bd\u30fc\u30b9\u89e3\u653e\u6642\u306b\u3001delete p\u306e\u4ee3\u308f\u308a\u306b\u30c7\u30ea\u30fc\u30bf\u304c\u547c\u3070\u308c\u308b\u3002\n std::shared_ptr<int> p3(new int(3), std::default_delete<int>());\n assert(*p3.get() == 3);\n assert(p3.use_count() == 1);\n\n // (4)\n // \u30dd\u30a4\u30f3\u30bf\u306e\u6240\u6709\u6a29\u3001\u30c7\u30ea\u30fc\u30bf\u3001\u30a2\u30ed\u30b1\u30fc\u30bf\u3092\u53d7\u3051\u53d6\u308b\u3002\n // \u30a2\u30ed\u30b1\u30fc\u30bf\u306f\u5185\u90e8\u7684\u306brebind\u3055\u308c\u308b\u306e\u3067\u3001\u8981\u7d20\u578b\u306f\u306a\u3093\u3067\u3082\u3044\u3044\u3002\n std::shared_ptr<int> p4(new int(3),\n std::default_delete<int>(),\n std::allocator<void>());\n assert(*p4.get() == 3);\n assert(p4.use_count() == 1);\n\n // (5)\n // \u30c7\u30ea\u30fc\u30bf\u3092\u53d7\u3051\u53d6\u308a\u3001\n // \u30cc\u30eb\u30dd\u30a4\u30f3\u30bf\u3092\u6240\u6709\u3059\u308bshared_ptr\u30aa\u30d6\u30b8\u30a7\u30af\u30c8\u3092\u69cb\u7bc9\u3059\u308b\u3002\n std::shared_ptr<int> p5(nullptr, std::default_delete<int>());\n assert(p5.get() == nullptr);\n assert(p5.use_count() == 1);\n\n // (6)\n // \u30c7\u30ea\u30fc\u30bf\u3068\u30a2\u30ed\u30b1\u30fc\u30bf\u3092\u53d7\u3051\u53d6\u308a\u3001\n // \u30cc\u30eb\u30dd\u30a4\u30f3\u30bf\u3092\u6240\u6709\u3059\u308bshared_ptr\u30aa\u30d6\u30b8\u30a7\u30af\u30c8\u3092\u69cb\u7bc9\u3059\u308b\u3002\n std::shared_ptr<int> p6(nullptr,\n std::default_delete<int>(),\n std::allocator<void>());\n assert(p6.get() == nullptr);\n assert(p6.use_count() == 1);\n\n // (7)\n // \u8981\u7d20\u578b\u306e\u30e1\u30f3\u30d0\u3078\u306e\u30dd\u30a4\u30f3\u30bf\u3092\u5171\u6709\u3059\u308b\u3002\n std::shared_ptr<X> p7_org(new X(3));\n std::shared_ptr<int> p7(p7_org, &(p7_org->i));\n assert(*p7.get() == 3); // p7\u306fi\u3078\u306e\u30dd\u30a4\u30f3\u30bf\u3092\u6240\u6709\u3059\u308b\n assert(p7.use_count() == p7_org.use_count()); // \u6240\u6709\u6a29\u306f\u30b3\u30d4\u30fc\u5143\u306eshared_ptr\u3068\u5171\u6709\u3059\u308b\n\n // (8)\n // \u4ed6\u306eshared_ptr\u3068\u30ea\u30bd\u30fc\u30b9\u3092\u5171\u6709\u3059\u308b\n std::shared_ptr<int> p8_org(new int(3));\n std::shared_ptr<int> p8 = p8_org;\n assert(p8.get() == p8_org.get()); // p8_org\u3068o8\u306f\u30ea\u30bd\u30fc\u30b9\u3092\u5171\u6709\u3059\u308b\n assert(p8.use_count() == 2); // \u6240\u6709\u8005\u306f2\u4eba\n\n // (10)\n // \u4ed6\u306eshared_ptr\u304b\u3089\u30ea\u30bd\u30fc\u30b9\u3092\u79fb\u52d5\u3059\u308b\n std::shared_ptr<int> p10_org(new int(3));\n std::shared_ptr<int> p10 = std::move(p10_org);\n assert(*p10.get() == 3);\n assert(p10.use_count() == 1);\n assert(p10_org.use_count() == 0);\n\n // (12)\n // weak_ptr\u304b\u3089\u69cb\u7bc9\n std::shared_ptr<int> p12_org(new int(3));\n std::weak_ptr<int> w12(p12_org);\n if (std::shared_ptr<int> p12 = w12.lock()) {\n assert(*p12.get() == 3);\n assert(p12.use_count() == 2);\n }\n else {\n assert(false);\n }\n\n // (14)\n // unique_ptr\u304b\u3089\u30ea\u30bd\u30fc\u30b9\u3092\u79fb\u52d5\u3059\u308b\n std::unique_ptr<int> p14_org(new int(3));\n std::shared_ptr<int> p14 = std::move(p14_org);\n assert(*p14.get() == 3);\n assert(p14.use_count() == 1);\n assert(p14_org.get() == nullptr);\n\n // (15)\n // \u7a7a\u306eshared_ptr\u3092\u69cb\u7bc9\u3059\u308b\n std::shared_ptr<int> p15 = nullptr;\n assert(p15.get() == nullptr);\n assert(p15.use_count() == 0);\n}\n"}, {"id": "aeea5eb56732373f2f78659358ab9977b87216cb", "source": "#include <cassert>\n#include <memory>\n#include <string>\n#include <utility>\n\nstruct Person {\n std::string name;\n int age;\n};\n\nint main()\n{\n std::shared_ptr<std::string> name;\n {\n std::shared_ptr<Person> person(new Person{\"Alice\", 25});\n\n // (7)\n // person\u3068\u6240\u6709\u6a29\u3092\u5171\u6709\u3057\u3064\u3064\u3001\u30e1\u30f3\u30d0\u5909\u6570name\u3092\u6307\u3059shared_ptr\u30aa\u30d6\u30b8\u30a7\u30af\u30c8\u3092\u69cb\u7bc9\u3059\u308b\n name = std::shared_ptr<std::string>(person, &person->name);\n assert(name.use_count() == 2);\n assert(*name == \"Alice\");\n }\n\n // person\u306f\u7834\u68c4\u3055\u308c\u305f\u304c\u3001name\u304c\u6240\u6709\u6a29\u3092\u3082\u3063\u3066\u3044\u308b\u305f\u3081\u3001\n // Person\u30aa\u30d6\u30b8\u30a7\u30af\u30c8\u5168\u4f53\u304c\u307e\u3060\u7834\u68c4\u3055\u308c\u3066\u3044\u306a\u3044\n assert(name.use_count() == 1);\n assert(*name == \"Alice\");\n\n // (16)\n // \u6240\u6709\u6a29\u3092\u79fb\u52d5\u3057\u3064\u3064\u3001\u30e1\u30f3\u30d0\u5909\u6570age\u3092\u6307\u3059shared_ptr\u30aa\u30d6\u30b8\u30a7\u30af\u30c8\u3092\u69cb\u7bc9\u3059\u308b\u3002\n // \u6240\u6709\u6a29\u306e\u79fb\u52d5\u306f\u30b3\u30f3\u30b9\u30c8\u30e9\u30af\u30bf\u306e\u4e2d\u3067\u884c\u308f\u308c\u308b\u305f\u3081\u3001\n // \u5b9f\u5f15\u6570&person->age\u306e\u8a55\u4fa1\u306f\u79fb\u52d5\u306e\u5f71\u97ff\u3092\u53d7\u3051\u306a\u3044\n std::shared_ptr<Person> person(new Person{\"Bob\", 30});\n std::shared_ptr<int> age(std::move(person), &person->age);\n assert(person.use_count() == 0);\n assert(person.get() == nullptr);\n assert(*age == 30);\n}\n"}], "page_id": ["reference", "memory", "shared_ptr", "op_constructor"]}">
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<div class="identifier-type">function</div><div class="header"><memory></div><h1 itemprop="name"><span class="namespace" title="namespace std">std::</span><span class="class" title="class shared_ptr">shared_ptr::</span><span class="token">コンストラクタ</span><span class="cpp cpp11" title="C++11で追加">(C++11)</span></h1>
<div itemprop="articleBody"><p><div class="codehilite"><pre><span></span><code><span class="k">constexpr</span>
<span class="n">shared_ptr</span><span class="p">()</span><span class="w"> </span><span class="k">noexcept</span><span class="p">;</span><span class="w"> </span><span class="c1">// (1) C++11</span>
<span class="k">template</span><span class="w"> </span><span class="o"><</span><span class="k">class</span><span class="w"> </span><span class="nc">Y</span><span class="o">></span>
<span class="k">explicit</span>
<span class="n">shared_ptr</span><span class="p">(</span><span class="n">Y</span><span class="o">*</span><span class="w"> </span><span class="n">p</span><span class="p">);</span><span class="w"> </span><span class="c1">// (2) C++11</span>
<span class="k">template</span><span class="w"> </span><span class="o"><</span><span class="k">class</span><span class="w"> </span><span class="nc">Y</span><span class="o">></span>
<span class="k">constexpr</span><span class="w"> </span><span class="k">explicit</span>
<span class="n">shared_ptr</span><span class="p">(</span><span class="n">Y</span><span class="o">*</span><span class="w"> </span><span class="n">p</span><span class="p">);</span><span class="w"> </span><span class="c1">// (2) C++26</span>
<span class="k">template</span><span class="w"> </span><span class="o"><</span><span class="k">class</span><span class="w"> </span><span class="nc">Y</span><span class="p">,</span><span class="w"> </span><span class="k">class</span><span class="w"> </span><span class="nc">Deleter</span><span class="o">></span>
<span class="n">shared_ptr</span><span class="p">(</span><span class="n">Y</span><span class="o">*</span><span class="w"> </span><span class="n">p</span><span class="p">,</span>
<span class="w"> </span><span class="n">Deleter</span><span class="w"> </span><span class="n">d</span><span class="p">);</span><span class="w"> </span><span class="c1">// (3) C++11</span>
<span class="k">template</span><span class="w"> </span><span class="o"><</span><span class="k">class</span><span class="w"> </span><span class="nc">Y</span><span class="p">,</span><span class="w"> </span><span class="k">class</span><span class="w"> </span><span class="nc">Deleter</span><span class="o">></span>
<span class="k">constexpr</span>
<span class="n">shared_ptr</span><span class="p">(</span><span class="n">Y</span><span class="o">*</span><span class="w"> </span><span class="n">p</span><span class="p">,</span>
<span class="w"> </span><span class="n">Deleter</span><span class="w"> </span><span class="n">d</span><span class="p">);</span><span class="w"> </span><span class="c1">// (3) C++26</span>
<span class="k">template</span><span class="w"> </span><span class="o"><</span><span class="k">class</span><span class="w"> </span><span class="nc">Y</span><span class="p">,</span><span class="w"> </span><span class="k">class</span><span class="w"> </span><span class="nc">Deleter</span><span class="p">,</span><span class="w"> </span><span class="k">class</span><span class="w"> </span><span class="nc">Alloc</span><span class="o">></span>
<span class="k">constexpr</span>
<span class="n">shared_ptr</span><span class="p">(</span><span class="n">Y</span><span class="o">*</span><span class="w"> </span><span class="n">p</span><span class="p">,</span>
<span class="w"> </span><span class="n">Deleter</span><span class="w"> </span><span class="n">d</span><span class="p">,</span>
<span class="w"> </span><span class="n">Alloc</span><span class="w"> </span><span class="n">a</span><span class="p">);</span><span class="w"> </span><span class="c1">// (4) C++11</span>
<span class="k">template</span><span class="w"> </span><span class="o"><</span><span class="k">class</span><span class="w"> </span><span class="nc">Y</span><span class="p">,</span><span class="w"> </span><span class="k">class</span><span class="w"> </span><span class="nc">Deleter</span><span class="p">,</span><span class="w"> </span><span class="k">class</span><span class="w"> </span><span class="nc">Alloc</span><span class="o">></span>
<span class="n">shared_ptr</span><span class="p">(</span><span class="n">Y</span><span class="o">*</span><span class="w"> </span><span class="n">p</span><span class="p">,</span>
<span class="w"> </span><span class="n">Deleter</span><span class="w"> </span><span class="n">d</span><span class="p">,</span>
<span class="w"> </span><span class="n">Alloc</span><span class="w"> </span><span class="n">a</span><span class="p">);</span><span class="w"> </span><span class="c1">// (4) C++26</span>
<span class="k">template</span><span class="w"> </span><span class="o"><</span><span class="k">class</span><span class="w"> </span><span class="nc">Deleter</span><span class="o">></span>
<span class="n">shared_ptr</span><span class="p">(</span><span class="n"><a href="../../cstddef/nullptr_t.html">nullptr_t</a></span><span class="w"> </span><span class="n">p</span><span class="p">,</span>
<span class="w"> </span><span class="n">Deleter</span><span class="w"> </span><span class="n">d</span><span class="p">);</span><span class="w"> </span><span class="c1">// (5) C++11</span>
<span class="k">template</span><span class="w"> </span><span class="o"><</span><span class="k">class</span><span class="w"> </span><span class="nc">Deleter</span><span class="o">></span>
<span class="k">constexpr</span>
<span class="n">shared_ptr</span><span class="p">(</span><span class="n"><a href="../../cstddef/nullptr_t.html">nullptr_t</a></span><span class="w"> </span><span class="n">p</span><span class="p">,</span>
<span class="w"> </span><span class="n">Deleter</span><span class="w"> </span><span class="n">d</span><span class="p">);</span><span class="w"> </span><span class="c1">// (5) C++26</span>
<span class="k">template</span><span class="w"> </span><span class="o"><</span><span class="k">class</span><span class="w"> </span><span class="nc">Deleter</span><span class="p">,</span><span class="w"> </span><span class="k">class</span><span class="w"> </span><span class="nc">Alloc</span><span class="o">></span>
<span class="n">shared_ptr</span><span class="p">(</span><span class="n"><a href="../../cstddef/nullptr_t.html">nullptr_t</a></span><span class="w"> </span><span class="n">p</span><span class="p">,</span>
<span class="w"> </span><span class="n">Deleter</span><span class="w"> </span><span class="n">d</span><span class="p">,</span>
<span class="w"> </span><span class="n">Alloc</span><span class="w"> </span><span class="n">a</span><span class="p">);</span><span class="w"> </span><span class="c1">// (6) C++11</span>
<span class="k">template</span><span class="w"> </span><span class="o"><</span><span class="k">class</span><span class="w"> </span><span class="nc">Deleter</span><span class="p">,</span><span class="w"> </span><span class="k">class</span><span class="w"> </span><span class="nc">Alloc</span><span class="o">></span>
<span class="k">constexpr</span>
<span class="n">shared_ptr</span><span class="p">(</span><span class="n"><a href="../../cstddef/nullptr_t.html">nullptr_t</a></span><span class="w"> </span><span class="n">p</span><span class="p">,</span>
<span class="w"> </span><span class="n">Deleter</span><span class="w"> </span><span class="n">d</span><span class="p">,</span>
<span class="w"> </span><span class="n">Alloc</span><span class="w"> </span><span class="n">a</span><span class="p">);</span><span class="w"> </span><span class="c1">// (6) C++26</span>
<span class="k">template</span><span class="o"><</span><span class="k">class</span><span class="w"> </span><span class="nc">Y</span><span class="o">></span>
<span class="n">shared_ptr</span><span class="p">(</span><span class="k">const</span><span class="w"> </span><span class="n">shared_ptr</span><span class="o"><</span><span class="n">Y</span><span class="o">>&</span><span class="w"> </span><span class="n">r</span><span class="p">,</span>
<span class="w"> </span><span class="n">T</span><span class="o">*</span><span class="w"> </span><span class="n">p</span><span class="p">)</span><span class="w"> </span><span class="k">noexcept</span><span class="p">;</span><span class="w"> </span><span class="c1">// (7) C++11</span>
<span class="k">template</span><span class="o"><</span><span class="k">class</span><span class="w"> </span><span class="nc">Y</span><span class="o">></span>
<span class="n">shared_ptr</span><span class="p">(</span><span class="k">const</span><span class="w"> </span><span class="n">shared_ptr</span><span class="o"><</span><span class="n">Y</span><span class="o">>&</span><span class="w"> </span><span class="n">r</span><span class="p">,</span>
<span class="w"> </span><span class="n">element_type</span><span class="o">*</span><span class="w"> </span><span class="n">p</span><span class="p">)</span><span class="w"> </span><span class="k">noexcept</span><span class="p">;</span><span class="w"> </span><span class="c1">// (7) C++17</span>
<span class="k">template</span><span class="o"><</span><span class="k">class</span><span class="w"> </span><span class="nc">Y</span><span class="o">></span>
<span class="k">constexpr</span>
<span class="n">shared_ptr</span><span class="p">(</span><span class="k">const</span><span class="w"> </span><span class="n">shared_ptr</span><span class="o"><</span><span class="n">Y</span><span class="o">>&</span><span class="w"> </span><span class="n">r</span><span class="p">,</span>
<span class="w"> </span><span class="n">element_type</span><span class="o">*</span><span class="w"> </span><span class="n">p</span><span class="p">)</span><span class="w"> </span><span class="k">noexcept</span><span class="p">;</span><span class="w"> </span><span class="c1">// (7) C++26</span>
<span class="n">shared_ptr</span><span class="p">(</span><span class="k">const</span><span class="w"> </span><span class="n">shared_ptr</span><span class="o">&</span><span class="w"> </span><span class="n">r</span><span class="p">)</span><span class="w"> </span><span class="k">noexcept</span><span class="p">;</span><span class="w"> </span><span class="c1">// (8) C++11</span>
<span class="k">constexpr</span>
<span class="n">shared_ptr</span><span class="p">(</span><span class="k">const</span><span class="w"> </span><span class="n">shared_ptr</span><span class="o">&</span><span class="w"> </span><span class="n">r</span><span class="p">)</span><span class="w"> </span><span class="k">noexcept</span><span class="p">;</span><span class="w"> </span><span class="c1">// (8) C++26</span>
<span class="k">template</span><span class="w"> </span><span class="o"><</span><span class="k">class</span><span class="w"> </span><span class="nc">Y</span><span class="o">></span>
<span class="n">shared_ptr</span><span class="p">(</span><span class="k">const</span><span class="w"> </span><span class="n">shared_ptr</span><span class="o"><</span><span class="n">Y</span><span class="o">>&</span><span class="w"> </span><span class="n">r</span><span class="p">)</span><span class="w"> </span><span class="k">noexcept</span><span class="p">;</span><span class="w"> </span><span class="c1">// (9) C++11</span>
<span class="k">template</span><span class="w"> </span><span class="o"><</span><span class="k">class</span><span class="w"> </span><span class="nc">Y</span><span class="o">></span>
<span class="k">constexpr</span>
<span class="n">shared_ptr</span><span class="p">(</span><span class="k">const</span><span class="w"> </span><span class="n">shared_ptr</span><span class="o"><</span><span class="n">Y</span><span class="o">>&</span><span class="w"> </span><span class="n">r</span><span class="p">)</span><span class="w"> </span><span class="k">noexcept</span><span class="p">;</span><span class="w"> </span><span class="c1">// (9) C++26</span>
<span class="n">shared_ptr</span><span class="p">(</span><span class="n">shared_ptr</span><span class="o">&&</span><span class="w"> </span><span class="n">r</span><span class="p">)</span><span class="w"> </span><span class="k">noexcept</span><span class="p">;</span><span class="w"> </span><span class="c1">// (10) C++11</span>
<span class="k">constexpr</span>
<span class="n">shared_ptr</span><span class="p">(</span><span class="n">shared_ptr</span><span class="o">&&</span><span class="w"> </span><span class="n">r</span><span class="p">)</span><span class="w"> </span><span class="k">noexcept</span><span class="p">;</span><span class="w"> </span><span class="c1">// (10) C++26</span>
<span class="k">template</span><span class="w"> </span><span class="o"><</span><span class="k">class</span><span class="w"> </span><span class="nc">Y</span><span class="o">></span>
<span class="n">shared_ptr</span><span class="p">(</span><span class="n">shared_ptr</span><span class="o"><</span><span class="n">Y</span><span class="o">>&&</span><span class="w"> </span><span class="n">r</span><span class="p">)</span><span class="w"> </span><span class="k">noexcept</span><span class="p">;</span><span class="w"> </span><span class="c1">// (11) C++11</span>
<span class="k">template</span><span class="w"> </span><span class="o"><</span><span class="k">class</span><span class="w"> </span><span class="nc">Y</span><span class="o">></span>
<span class="k">constexpr</span>
<span class="n">shared_ptr</span><span class="p">(</span><span class="n">shared_ptr</span><span class="o"><</span><span class="n">Y</span><span class="o">>&&</span><span class="w"> </span><span class="n">r</span><span class="p">)</span><span class="w"> </span><span class="k">noexcept</span><span class="p">;</span><span class="w"> </span><span class="c1">// (11) C++26</span>
<span class="k">template</span><span class="w"> </span><span class="o"><</span><span class="k">class</span><span class="w"> </span><span class="nc">Y</span><span class="o">></span>
<span class="k">explicit</span>
<span class="n">shared_ptr</span><span class="p">(</span><span class="k">const</span><span class="w"> </span><span class="n"><a href="../weak_ptr.html">weak_ptr</a></span><span class="o"><</span><span class="n">Y</span><span class="o">>&</span><span class="w"> </span><span class="n">r</span><span class="p">);</span><span class="w"> </span><span class="c1">// (12) C++11</span>
<span class="k">template</span><span class="w"> </span><span class="o"><</span><span class="k">class</span><span class="w"> </span><span class="nc">Y</span><span class="o">></span>
<span class="k">constexpr</span><span class="w"> </span><span class="k">explicit</span>
<span class="n">shared_ptr</span><span class="p">(</span><span class="k">const</span><span class="w"> </span><span class="n"><a href="../weak_ptr.html">weak_ptr</a></span><span class="o"><</span><span class="n">Y</span><span class="o">>&</span><span class="w"> </span><span class="n">r</span><span class="p">);</span><span class="w"> </span><span class="c1">// (12) C++26</span>
<span class="k">template</span><span class="w"> </span><span class="o"><</span><span class="k">class</span><span class="w"> </span><span class="nc">Y</span><span class="o">></span>
<span class="n">shared_ptr</span><span class="p">(</span><span class="n">auto_ptr</span><span class="o"><</span><span class="n">Y</span><span class="o">>&&</span><span class="w"> </span><span class="n">r</span><span class="p">);</span><span class="w"> </span><span class="c1">// (13)</span>
<span class="w"> </span><span class="c1">// C++11から非推奨</span>
<span class="w"> </span><span class="c1">// C++17で削除</span>
<span class="k">template</span><span class="w"> </span><span class="o"><</span><span class="k">class</span><span class="w"> </span><span class="nc">Y</span><span class="p">,</span><span class="w"> </span><span class="k">class</span><span class="w"> </span><span class="nc">Deleter</span><span class="o">></span>
<span class="n">shared_ptr</span><span class="p">(</span><span class="n"><a href="../unique_ptr.html">unique_ptr</a></span><span class="o"><</span><span class="n">Y</span><span class="p">,</span><span class="w"> </span><span class="n">Deleter</span><span class="o">>&&</span><span class="w"> </span><span class="n">r</span><span class="p">);</span><span class="w"> </span><span class="c1">// (14) C++11</span>
<span class="k">template</span><span class="w"> </span><span class="o"><</span><span class="k">class</span><span class="w"> </span><span class="nc">Y</span><span class="p">,</span><span class="w"> </span><span class="k">class</span><span class="w"> </span><span class="nc">Deleter</span><span class="o">></span>
<span class="k">constexpr</span>
<span class="n">shared_ptr</span><span class="p">(</span><span class="n"><a href="../unique_ptr.html">unique_ptr</a></span><span class="o"><</span><span class="n">Y</span><span class="p">,</span><span class="w"> </span><span class="n">Deleter</span><span class="o">>&&</span><span class="w"> </span><span class="n">r</span><span class="p">);</span><span class="w"> </span><span class="c1">// (14) C++26</span>
<span class="k">constexpr</span><span class="w"> </span><span class="n">shared_ptr</span><span class="p">(</span><span class="n"><a href="../../cstddef/nullptr_t.html">nullptr_t</a></span><span class="p">);</span><span class="w"> </span><span class="c1">// (15) C++14</span>
<span class="k">constexpr</span><span class="w"> </span><span class="n">shared_ptr</span><span class="p">(</span><span class="n"><a href="../../cstddef/nullptr_t.html">nullptr_t</a></span><span class="p">)</span><span class="w"> </span><span class="k">noexcept</span><span class="p">;</span><span class="w"> </span><span class="c1">// (15) C++17</span>
<span class="k">template</span><span class="w"> </span><span class="o"><</span><span class="k">class</span><span class="w"> </span><span class="nc">Y</span><span class="o">></span>
<span class="n">shared_ptr</span><span class="p">(</span><span class="n">shared_ptr</span><span class="o"><</span><span class="n">Y</span><span class="o">>&&</span><span class="w"> </span><span class="n">r</span><span class="p">,</span>
<span class="w"> </span><span class="n">element_type</span><span class="o">*</span><span class="w"> </span><span class="n">p</span><span class="p">)</span><span class="w"> </span><span class="k">noexcept</span><span class="p">;</span><span class="w"> </span><span class="c1">// (16) C++20</span>
<span class="k">template</span><span class="w"> </span><span class="o"><</span><span class="k">class</span><span class="w"> </span><span class="nc">Y</span><span class="o">></span>
<span class="k">constexpr</span>
<span class="n">shared_ptr</span><span class="p">(</span><span class="n">shared_ptr</span><span class="o"><</span><span class="n">Y</span><span class="o">>&&</span><span class="w"> </span><span class="n">r</span><span class="p">,</span>
<span class="w"> </span><span class="n">element_type</span><span class="o">*</span><span class="w"> </span><span class="n">p</span><span class="p">)</span><span class="w"> </span><span class="k">noexcept</span><span class="p">;</span><span class="w"> </span><span class="c1">// (16) C++26</span>
</code></pre></div>
</p>
<h2><code>shared_ptr</code>オブジェクトの構築</h2>
<ul>
<li>(1) : 所有権を持たない、空の<code>shared_ptr</code>オブジェクトを構築する。</li>
<li>(2) : 生ポインタの所有権を受け取る。</li>
<li>(3) : 生ポインタの所有権と、リソースを破棄する際に使用する関数オブジェクトを受け取る。</li>
<li>(4) : 生ポインタの所有権、リソースを破棄する際に使用する関数オブジェクト、アロケータを受け取る。</li>
<li>(5) : リソースを破棄する際に使用する関数オブジェクトを受け取り、ヌルポインタを所有する<code>shared_ptr</code>オブジェクトを構築する。</li>
<li>(6) : リソースを破棄する際に使用する関数オブジェクトと、アロケータを受け取り、ヌルポインタを所有する<code>shared_ptr</code>オブジェクトを構築する。</li>
<li>(7) : 他の<code>shared_ptr</code>オブジェクトとリソースを共有し、保持するポインタを個別に指定する(エイリアシングコンストラクタ)。</li>
<li>(8), (9) : 他の<code>shared_ptr</code>オブジェクトと、リソースを共有する。</li>
<li>(10), (11) : 他の<code>shared_ptr</code>オブジェクトから、リソースの所有権を移動する。</li>
<li>(12) : <code><a href="../weak_ptr.html">weak_ptr</a></code>オブジェクトが参照するリソースから、所有権を共有する<code>shared_ptr</code>オブジェクトを構築する。</li>
<li>(13) : <code>auto_ptr</code>オブジェクトから、リソースの所有権を移動する。</li>
<li>(14) : <code><a href="../unique_ptr.html">unique_ptr</a></code>オブジェクトから、リソースの所有権を移動する。</li>
<li>(15) : (1)と同じく、所有権を持たない、空の<code>shared_ptr</code>オブジェクトを構築する。</li>
<li>(16) : 他の<code>shared_ptr</code>オブジェクトからリソースの所有権を移動し、保持するポインタを個別に指定する(エイリアシングコンストラクタ)。</li>
</ul>
<h2>要件</h2>
<ul>
<li>(2) C++11 :<ul>
<li><code>p</code>が<code>T*</code>に変換可能であること。</li>
<li><code>Y</code>が<a class="cpprefjp-defined-word" data-desc="型のサイズを決定できる型。不完全型ではない型">完全型</a>であること。</li>
<li>式<code>delete p</code>が妥当であること。</li>
</ul>
</li>
<li>(2) C++17 :<ul>
<li><code>p</code>が<code>T*</code>と互換があること。</li>
<li><code>Y</code>が<a class="cpprefjp-defined-word" data-desc="型のサイズを決定できる型。不完全型ではない型">完全型</a>であること。</li>
<li>型<code>T</code>が非配列である場合、式<code>delete p</code>が妥当であること。</li>
<li>型<code>T</code>が配列である場合、式<code>delete[] p</code>が妥当であること。</li>
<li>型<code>T</code>が<code>U[N]</code>形式である場合、関数ポインタ配列<code>Y(*)[N]</code>は<code>T*</code>に変換可能である。</li>
<li>型<code>T</code>が<code>U[]</code>形式である場合、関数ポインタ配列<code>Y(*)[]</code>は<code>T*</code>に変換可能である。</li>
</ul>
</li>
<li>(3), (4), (5), (6) : <code>p</code>が<code>T*</code>に変換可能であること。<code>d</code>および<code>std::<a href="../../utility/move.html">move</a>(d)</code>から型<code>Deleter</code>の削除子を構築する操作が<a class="cpprefjp-defined-word" data-desc="問題が発生したときに、現在実行位置を過去に通過・記録した位置に戻し、文脈情報を添えて紐づけられた処理(例外ハンドラー)を呼び出す仕組み。またはその事態">例外</a>を投げないこと。<code>d(p)</code>という式が<a class="cpprefjp-defined-word" data-desc="プログラムが文法規則・診断対象の意味規則・単一定義規則を満たすこと" href="../../../implementation-compliance.html#dfn-well-formed">適格</a>であり、定義された動作をし、<a class="cpprefjp-defined-word" data-desc="問題が発生したときに、現在実行位置を過去に通過・記録した位置に戻し、文脈情報を添えて紐づけられた処理(例外ハンドラー)を呼び出す仕組み。またはその事態">例外</a>を投げないこと。<ul>
<li>C++11 : <code>Deleter</code>がコピー構築可能であること</li>
<li>C++17 : <code>Deleter</code>がムーブ構築可能であること。また、<code>Deleter</code>のデストラクタが<a class="cpprefjp-defined-word" data-desc="問題が発生したときに、現在実行位置を過去に通過・記録した位置に戻し、文脈情報を添えて紐づけられた処理(例外ハンドラー)を呼び出す仕組み。またはその事態">例外</a>を投げないという要件は削除された</li>
<li>C++17 : 型<code>T</code>が配列である場合、式<code>delete[] p</code>が妥当であること。型<code>T</code>が<code>U[N]</code>形式である場合、関数ポインタ配列<code>Y(*)[N]</code>は<code>T*</code>に変換可能である。</li>
</ul>
</li>
<li>(9) C++11 : <code>Y*</code>が<code>T*</code>に暗黙変換可能でない場合、この関数は<a class="cpprefjp-defined-word" data-desc="関数呼び出し時に、同名の関数の中から実際に呼び出す関数を決定する処理。このときの候補になることを、オーバーロード解決に参加するという">オーバーロード解決</a>から除外される。</li>
<li>(9) C++17 : <code>Y*</code>が<code>T*</code>と互換でない場合、この関数は<a class="cpprefjp-defined-word" data-desc="関数呼び出し時に、同名の関数の中から実際に呼び出す関数を決定する処理。このときの候補になることを、オーバーロード解決に参加するという">オーバーロード解決</a>から除外される。</li>
<li>(11) : <code>Y*</code>が<code>T*</code>に暗黙変換可能でない場合、この関数は<a class="cpprefjp-defined-word" data-desc="関数呼び出し時に、同名の関数の中から実際に呼び出す関数を決定する処理。このときの候補になることを、オーバーロード解決に参加するという">オーバーロード解決</a>から除外される。</li>
<li>(12) C++11 : <code>Y*</code>が<code>T*</code>に変換可能であること。</li>
<li>(12) C++17 : <code>Y*</code>が<code>T*</code>と互換であること。</li>
<li>(13) : <code>r.release()</code>によって返されるポインタ値が、<code>T*</code>に変換可能であること。<code>Y</code>が<a class="cpprefjp-defined-word" data-desc="型のサイズを決定できる型。不完全型ではない型">完全型</a>であり、式<code>delete r.release()</code>が妥当であること。</li>
<li>(14) C++11 : <code>unique_ptr<Y, Deleter>::pointer</code>が<code>T*</code>に変換可能でない場合、この関数は<a class="cpprefjp-defined-word" data-desc="関数呼び出し時に、同名の関数の中から実際に呼び出す関数を決定する処理。このときの候補になることを、オーバーロード解決に参加するという">オーバーロード解決</a>から除外される。</li>
<li>(14) C++17 : <code>Y*</code>が<code>T*</code>と互換でなく、<code>unique_ptr<Y, Deleter>::pointer</code>が<code>element_type*</code>に変換可能でない場合、この関数は<a class="cpprefjp-defined-word" data-desc="関数呼び出し時に、同名の関数の中から実際に呼び出す関数を決定する処理。このときの候補になることを、オーバーロード解決に参加するという">オーバーロード解決</a>から除外される。</li>
</ul>
<h2>効果</h2>
<ul>
<li>(1) : 空の<code>shared_ptr</code>オブジェクトを構築する。</li>
<li>(2) C++11 : ポインタ<code>p</code>を所有する<code>shared_ptr</code>オブジェクトを構築する。</li>
<li>(2) C++17 : 型<code>T</code>が配列ではない場合、ポインタ<code>p</code>を所有する<code>shared_ptr</code>オブジェクトを構築する。そうではない場合、ポインタ<code>p</code>と、<code>delete[] p</code>を実行するデリータを所有する<code>shared_ptr</code>オブジェクトを構築する。</li>
<li>(3) : リソースを破棄する際に使用する関数オブジェクト<code>d</code>を受け取り、ポインタ<code>p</code>を所有する<code>shared_ptr</code>オブジェクトを構築する。</li>
<li>(4) : リソースを破棄する際に使用する関数オブジェクト<code>d</code>を受け取り、ポインタ<code>p</code>を所有する<code>shared_ptr</code>オブジェクトを構築する。アロケータオブジェクト<code>a</code>のコピーを、内部のメモリ確保に使用する。</li>
<li>(5) : リソースを破棄する際に使用する関数オブジェクト<code>d</code>を受け取り、ヌルポインタを所有する<code>shared_ptr</code>オブジェクトを構築する。</li>
<li>(6) : リソースを破棄する際に使用する関数オブジェクト<code>d</code>を受け取り、ヌルポインタを所有する<code>shared_ptr</code>オブジェクトを構築する。アロケータオブジェクト<code>a</code>のコピーを、内部のメモリ確保に使用する。</li>
<li>(7) : <code>r</code>と所有権を共有し、ポインタとしては<code>p</code>を保持する<code>shared_ptr</code>オブジェクトを構築する。</li>
<li>(8), (9) : <code>r</code>が空の場合、空の<code>shared_ptr</code>オブジェクトを構築する。そうでなければ、<code>r</code>とリソースを共有する<code>shared_ptr</code>オブジェクトを構築する。</li>
<li>(10), (11) : <code>r</code>が持つ所有権を、<code>*this</code>に移動する。</li>
<li>(12) : <code>r</code>が持つポインタのコピーを共有する<code>shared_ptr</code>オブジェクトを構築する。</li>
<li>(13) : <code>r</code>が持つ所有権を、<code>*this</code>に移動する。</li>
<li>(14) : 以下のように、(3)のコンストラクタに委譲する。<code>Deleter</code>が参照型でなければ<code>shared_ptr(r.<a href="../unique_ptr/release.html">release()</a>, r.<a href="../unique_ptr/get_deleter.html">get_deleter()</a>)</code>を呼び出し、そうでなければ<code>shared_ptr(r.<a href="../unique_ptr/release.html">release()</a>, <a href="../../functional/ref.html">ref</a>(r.<a href="../unique_ptr/get_deleter.html">get_deleter()</a>))</code></li>
<li>(15) : 空の<code>shared_ptr</code>オブジェクトを構築する。</li>
<li>(16) : <code>r</code>が持つ所有権を<code>*this</code>に移動し、ポインタとしては<code>p</code>を保持する<code>shared_ptr</code>オブジェクトを構築する。</li>
</ul>
<h2><a class="cpprefjp-defined-word" data-desc="関数等の意味論を構成する要素の1つ。Postconditions。関数を実行後に満たされている条件。契約属性の`[[ensures]]`に相当">事後条件</a></h2>
<ul>
<li>(1) : <code><a href="use_count.html">use_count()</a> == 0 && <a href="get.html">get()</a> == nullptr</code></li>
<li>(2), (3), (4) : <code><a href="use_count.html">use_count()</a> == 1 && <a href="get.html">get()</a> == p</code></li>
<li>(5), (6) : <code><a href="use_count.html">use_count()</a> == 1 && <a href="get.html">get()</a> == nullptr</code></li>
<li>(7) : <code><a href="get.html">get()</a> == p</code></li>
<li>(8), (9) : <code><a href="get.html">get()</a> == <a href="get.html">get()</a> && <a href="use_count.html">use_count()</a> == r.<a href="use_count.html">use_count()</a></code></li>
<li>(10) : <code>*this</code>は<code>r</code>がこれまで持っていた値を持ち、<code>r</code>は空の状態になる。</li>
<li>(12) : <code><a href="use_count.html">use_count()</a> == r.<a href="use_count.html">use_count()</a></code></li>
<li>(13) : <code><a href="use_count.html">use_count()</a> == 1 && r.<a href="get.html">get()</a> == nullptr</code></li>
<li>(16) :<ul>
<li><code><a href="get.html">get()</a> == p</code></li>
<li><code>r</code>が空になり、<code>r.<a href="get.html">get()</a> == nullptr</code></li>
</ul>
</li>
</ul>
<h2><a class="cpprefjp-defined-word" data-desc="問題が発生したときに、現在実行位置を過去に通過・記録した位置に戻し、文脈情報を添えて紐づけられた処理(例外ハンドラー)を呼び出す仕組み。またはその事態">例外</a></h2>
<ul>
<li>(3), (4), (5), (6) : メモリ確保に失敗した場合、<code><a href="../../new/bad_alloc.html">bad_alloc</a></code><a class="cpprefjp-defined-word" data-desc="問題が発生したときに、現在実行位置を過去に通過・記録した位置に戻し、文脈情報を添えて紐づけられた処理(例外ハンドラー)を呼び出す仕組み。またはその事態">例外</a>を送出する。<a class="cpprefjp-defined-word" data-desc="問題が発生したときに、現在実行位置を過去に通過・記録した位置に戻し、文脈情報を添えて紐づけられた処理(例外ハンドラー)を呼び出す仕組み。またはその事態">例外</a>送出時には<code>d(p)</code>を呼び出すことが保証される。</li>
<li>(12) : <code>r.<a href="../weak_ptr/expired.html">expired()</a> == true</code>の場合、<code><a href="../bad_weak_ptr.html">bad_weak_ptr</a></code><a class="cpprefjp-defined-word" data-desc="問題が発生したときに、現在実行位置を過去に通過・記録した位置に戻し、文脈情報を添えて紐づけられた処理(例外ハンドラー)を呼び出す仕組み。またはその事態">例外</a>を送出する。</li>
<li>(13) : メモリ確保に失敗した場合、<code><a href="../../new/bad_alloc.html">bad_alloc</a></code>もしくはその他<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>の<a class="cpprefjp-defined-word" data-desc="問題が発生したときに、現在実行位置を過去に通過・記録した位置に戻し、文脈情報を添えて紐づけられた処理(例外ハンドラー)を呼び出す仕組み。またはその事態">例外</a>を送出する。</li>
</ul>
<h2>備考</h2>
<ul>
<li>アロケータは、参照カウンタのメモリ確保に使用される。</li>
<li>(7), (16) : これらはエイリアシングコンストラクタ (aliasing constructor) と呼ばれる。所有権は<code>r</code>と共有((16)は<code>r</code>から移動)したまま、保持するポインタだけを<code>p</code>に差し替えた<code>shared_ptr</code>オブジェクトを構築する<ul>
<li>あるオブジェクトのメンバ変数や基底クラス部分オブジェクト、コンテナの要素を指す<code>shared_ptr</code>オブジェクトを作りつつ、それらを含むオブジェクト全体の寿命を延ばす用途で使用する</li>
<li>リソースの破棄は<code>r</code>が持つ削除子によって行われる。<code>p</code>が指すオブジェクトが破棄されるわけではない</li>
<li><code>p</code>は、<code>r</code>が所有するオブジェクトと関係のないポインタであってもよい。ただし、<code>r</code>の所有権グループが破棄されるまで<code>p</code>が妥当であり続けない場合、<a class="cpprefjp-defined-word" data-desc="dangling。寿命が尽きた無効なオブジェクトやメモリ領域を、ポインタ・参照・イテレータなどが指し続けている状態のこと。これらにアクセスすると未定義の動作を引き起こす">ダングリング</a>ポインタとなる</li>
<li><code>r</code>が空である場合は、<code>r</code>と同じく所有権をもたないが、<code>p</code>を保持する<code>shared_ptr</code>オブジェクトが構築される(<code><a href="use_count.html">use_count()</a> == 0</code>かつ<code><a href="get.html">get()</a> != nullptr</code>となる)</li>
</ul>
</li>
</ul>
<h2>例</h2>
<h3>基本的な使い方</h3>
<p><div class="yata" id="2c065dc109ebb79554cf786f320995e7069d65ba"><div class="codehilite"><pre><span></span><code><span class="cp">#include <a href="../../cassert.html"><cassert></a></span>
<span class="cp">#include <a href="../../memory.html"><memory></a></span>
<span class="cp">#include <a href="../../utility.html"><utility></a></span>
<span class="k">struct</span><span class="w"> </span><span class="nc">X</span><span class="w"> </span><span class="p">{</span>
<span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="p">;</span>
<span class="w"> </span><span class="n">X</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">0</span><span class="p">)</span>
<span class="w"> </span><span class="o">:</span><span class="w"> </span><span class="n">i</span><span class="p">(</span><span class="n">i</span><span class="p">)</span><span class="w"> </span><span class="p">{}</span>
<span class="p">};</span>
<span class="kt">int</span><span class="w"> </span><span class="nf">main</span><span class="p">()</span>
<span class="p">{</span>
<span class="w"> </span><span class="c1">// (1)</span>
<span class="w"> </span><span class="c1">// デフォルト構築。</span>
<span class="w"> </span><span class="c1">// 空のshared_ptrオブジェクトを構築する</span>
<span class="w"> </span><span class="n"><a href="../shared_ptr.html">std::shared_ptr</a></span><span class="o"><</span><span class="kt">int</span><span class="o">></span><span class="w"> </span><span class="n">p1</span><span class="p">;</span>
<span class="w"> </span><span class="n"><a href="../../cassert/assert.html">assert</a></span><span class="p">(</span><span class="n">p1</span><span class="p">.</span><span class="n"><a href="get.html">get()</a></span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="nb">nullptr</span><span class="p">);</span>
<span class="w"> </span><span class="n"><a href="../../cassert/assert.html">assert</a></span><span class="p">(</span><span class="n">p1</span><span class="p">.</span><span class="n"><a href="use_count.html">use_count()</a></span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="mi">0</span><span class="p">);</span>
<span class="w"> </span><span class="c1">// (2)</span>
<span class="w"> </span><span class="c1">// ポインタの所有権を受け取る。</span>
<span class="w"> </span><span class="n"><a href="../shared_ptr.html">std::shared_ptr</a></span><span class="o"><</span><span class="kt">int</span><span class="o">></span><span class="w"> </span><span class="n">p2</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="kt">int</span><span class="p">(</span><span class="mi">3</span><span class="p">));</span>
<span class="w"> </span><span class="n"><a href="../../cassert/assert.html">assert</a></span><span class="p">(</span><span class="o">*</span><span class="n">p2</span><span class="p">.</span><span class="n"><a href="get.html">get()</a></span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="mi">3</span><span class="p">);</span>
<span class="w"> </span><span class="n"><a href="../../cassert/assert.html">assert</a></span><span class="p">(</span><span class="n">p2</span><span class="p">.</span><span class="n"><a href="use_count.html">use_count()</a></span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="mi">1</span><span class="p">);</span>
<span class="w"> </span><span class="c1">// (3)</span>
<span class="w"> </span><span class="c1">// ポインタの所有権と、デリータを受け取る。</span>
<span class="w"> </span><span class="c1">// リソース解放時に、delete pの代わりにデリータが呼ばれる。</span>
<span class="w"> </span><span class="n"><a href="../shared_ptr.html">std::shared_ptr</a></span><span class="o"><</span><span class="kt">int</span><span class="o">></span><span class="w"> </span><span class="n">p3</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="kt">int</span><span class="p">(</span><span class="mi">3</span><span class="p">),</span><span class="w"> </span><span class="n"><a href="../default_delete.html">std::default_delete</a></span><span class="o"><</span><span class="kt">int</span><span class="o">></span><span class="p">());</span>
<span class="w"> </span><span class="n"><a href="../../cassert/assert.html">assert</a></span><span class="p">(</span><span class="o">*</span><span class="n">p3</span><span class="p">.</span><span class="n"><a href="get.html">get()</a></span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="mi">3</span><span class="p">);</span>
<span class="w"> </span><span class="n"><a href="../../cassert/assert.html">assert</a></span><span class="p">(</span><span class="n">p3</span><span class="p">.</span><span class="n"><a href="use_count.html">use_count()</a></span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="mi">1</span><span class="p">);</span>
<span class="w"> </span><span class="c1">// (4)</span>
<span class="w"> </span><span class="c1">// ポインタの所有権、デリータ、アロケータを受け取る。</span>
<span class="w"> </span><span class="c1">// アロケータは内部的にrebindされるので、要素型はなんでもいい。</span>
<span class="w"> </span><span class="n"><a href="../shared_ptr.html">std::shared_ptr</a></span><span class="o"><</span><span class="kt">int</span><span class="o">></span><span class="w"> </span><span class="n">p4</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="kt">int</span><span class="p">(</span><span class="mi">3</span><span class="p">),</span>
<span class="w"> </span><span class="n"><a href="../default_delete.html">std::default_delete</a></span><span class="o"><</span><span class="kt">int</span><span class="o">></span><span class="p">(),</span>
<span class="w"> </span><span class="n"><a href="../allocator.html">std::allocator</a></span><span class="o"><</span><span class="kt">void</span><span class="o">></span><span class="p">());</span>
<span class="w"> </span><span class="n"><a href="../../cassert/assert.html">assert</a></span><span class="p">(</span><span class="o">*</span><span class="n">p4</span><span class="p">.</span><span class="n"><a href="get.html">get()</a></span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="mi">3</span><span class="p">);</span>
<span class="w"> </span><span class="n"><a href="../../cassert/assert.html">assert</a></span><span class="p">(</span><span class="n">p4</span><span class="p">.</span><span class="n"><a href="use_count.html">use_count()</a></span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="mi">1</span><span class="p">);</span>
<span class="w"> </span><span class="c1">// (5)</span>
<span class="w"> </span><span class="c1">// デリータを受け取り、</span>
<span class="w"> </span><span class="c1">// ヌルポインタを所有するshared_ptrオブジェクトを構築する。</span>
<span class="w"> </span><span class="n"><a href="../shared_ptr.html">std::shared_ptr</a></span><span class="o"><</span><span class="kt">int</span><span class="o">></span><span class="w"> </span><span class="n">p5</span><span class="p">(</span><span class="nb">nullptr</span><span class="p">,</span><span class="w"> </span><span class="n"><a href="../default_delete.html">std::default_delete</a></span><span class="o"><</span><span class="kt">int</span><span class="o">></span><span class="p">());</span>
<span class="w"> </span><span class="n"><a href="../../cassert/assert.html">assert</a></span><span class="p">(</span><span class="n">p5</span><span class="p">.</span><span class="n"><a href="get.html">get()</a></span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="nb">nullptr</span><span class="p">);</span>
<span class="w"> </span><span class="n"><a href="../../cassert/assert.html">assert</a></span><span class="p">(</span><span class="n">p5</span><span class="p">.</span><span class="n"><a href="use_count.html">use_count()</a></span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="mi">1</span><span class="p">);</span>
<span class="w"> </span><span class="c1">// (6)</span>
<span class="w"> </span><span class="c1">// デリータとアロケータを受け取り、</span>
<span class="w"> </span><span class="c1">// ヌルポインタを所有するshared_ptrオブジェクトを構築する。</span>
<span class="w"> </span><span class="n"><a href="../shared_ptr.html">std::shared_ptr</a></span><span class="o"><</span><span class="kt">int</span><span class="o">></span><span class="w"> </span><span class="n">p6</span><span class="p">(</span><span class="nb">nullptr</span><span class="p">,</span>
<span class="w"> </span><span class="n"><a href="../default_delete.html">std::default_delete</a></span><span class="o"><</span><span class="kt">int</span><span class="o">></span><span class="p">(),</span>
<span class="w"> </span><span class="n"><a href="../allocator.html">std::allocator</a></span><span class="o"><</span><span class="kt">void</span><span class="o">></span><span class="p">());</span>
<span class="w"> </span><span class="n"><a href="../../cassert/assert.html">assert</a></span><span class="p">(</span><span class="n">p6</span><span class="p">.</span><span class="n"><a href="get.html">get()</a></span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="nb">nullptr</span><span class="p">);</span>
<span class="w"> </span><span class="n"><a href="../../cassert/assert.html">assert</a></span><span class="p">(</span><span class="n">p6</span><span class="p">.</span><span class="n"><a href="use_count.html">use_count()</a></span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="mi">1</span><span class="p">);</span>
<span class="w"> </span><span class="c1">// (7)</span>
<span class="w"> </span><span class="c1">// 要素型のメンバへのポインタを共有する。</span>
<span class="w"> </span><span class="n"><a href="../shared_ptr.html">std::shared_ptr</a></span><span class="o"><</span><span class="n">X</span><span class="o">></span><span class="w"> </span><span class="n">p7_org</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">X</span><span class="p">(</span><span class="mi">3</span><span class="p">));</span>
<span class="w"> </span><span class="n"><a href="../shared_ptr.html">std::shared_ptr</a></span><span class="o"><</span><span class="kt">int</span><span class="o">></span><span class="w"> </span><span class="n">p7</span><span class="p">(</span><span class="n">p7_org</span><span class="p">,</span><span class="w"> </span><span class="o">&</span><span class="p">(</span><span class="n">p7_org</span><span class="o">-></span><span class="n">i</span><span class="p">));</span>
<span class="w"> </span><span class="n"><a href="../../cassert/assert.html">assert</a></span><span class="p">(</span><span class="o">*</span><span class="n">p7</span><span class="p">.</span><span class="n"><a href="get.html">get()</a></span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="mi">3</span><span class="p">);</span><span class="w"> </span><span class="c1">// p7はiへのポインタを所有する</span>
<span class="w"> </span><span class="n"><a href="../../cassert/assert.html">assert</a></span><span class="p">(</span><span class="n">p7</span><span class="p">.</span><span class="n"><a href="use_count.html">use_count()</a></span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">p7_org</span><span class="p">.</span><span class="n"><a href="use_count.html">use_count()</a></span><span class="p">);</span><span class="w"> </span><span class="c1">// 所有権はコピー元のshared_ptrと共有する</span>
<span class="w"> </span><span class="c1">// (8)</span>
<span class="w"> </span><span class="c1">// 他のshared_ptrとリソースを共有する</span>
<span class="w"> </span><span class="n"><a href="../shared_ptr.html">std::shared_ptr</a></span><span class="o"><</span><span class="kt">int</span><span class="o">></span><span class="w"> </span><span class="n">p8_org</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="kt">int</span><span class="p">(</span><span class="mi">3</span><span class="p">));</span>
<span class="w"> </span><span class="n"><a href="../shared_ptr.html">std::shared_ptr</a></span><span class="o"><</span><span class="kt">int</span><span class="o">></span><span class="w"> </span><span class="n">p8</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">p8_org</span><span class="p">;</span>
<span class="w"> </span><span class="n"><a href="../../cassert/assert.html">assert</a></span><span class="p">(</span><span class="n">p8</span><span class="p">.</span><span class="n"><a href="get.html">get()</a></span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">p8_org</span><span class="p">.</span><span class="n"><a href="get.html">get()</a></span><span class="p">);</span><span class="w"> </span><span class="c1">// p8_orgとo8はリソースを共有する</span>
<span class="w"> </span><span class="n"><a href="../../cassert/assert.html">assert</a></span><span class="p">(</span><span class="n">p8</span><span class="p">.</span><span class="n"><a href="use_count.html">use_count()</a></span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="mi">2</span><span class="p">);</span><span class="w"> </span><span class="c1">// 所有者は2人</span>
<span class="w"> </span><span class="c1">// (10)</span>
<span class="w"> </span><span class="c1">// 他のshared_ptrからリソースを移動する</span>
<span class="w"> </span><span class="n"><a href="../shared_ptr.html">std::shared_ptr</a></span><span class="o"><</span><span class="kt">int</span><span class="o">></span><span class="w"> </span><span class="n">p10_org</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="kt">int</span><span class="p">(</span><span class="mi">3</span><span class="p">));</span>
<span class="w"> </span><span class="n"><a href="../shared_ptr.html">std::shared_ptr</a></span><span class="o"><</span><span class="kt">int</span><span class="o">></span><span class="w"> </span><span class="n">p10</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n"><a href="../../utility/move.html">std::move</a></span><span class="p">(</span><span class="n">p10_org</span><span class="p">);</span>
<span class="w"> </span><span class="n"><a href="../../cassert/assert.html">assert</a></span><span class="p">(</span><span class="o">*</span><span class="n">p10</span><span class="p">.</span><span class="n"><a href="get.html">get()</a></span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="mi">3</span><span class="p">);</span>
<span class="w"> </span><span class="n"><a href="../../cassert/assert.html">assert</a></span><span class="p">(</span><span class="n">p10</span><span class="p">.</span><span class="n"><a href="use_count.html">use_count()</a></span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="mi">1</span><span class="p">);</span>
<span class="w"> </span><span class="n"><a href="../../cassert/assert.html">assert</a></span><span class="p">(</span><span class="n">p10_org</span><span class="p">.</span><span class="n"><a href="use_count.html">use_count()</a></span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="mi">0</span><span class="p">);</span>
<span class="w"> </span><span class="c1">// (12)</span>
<span class="w"> </span><span class="c1">// weak_ptrから構築</span>
<span class="w"> </span><span class="n"><a href="../shared_ptr.html">std::shared_ptr</a></span><span class="o"><</span><span class="kt">int</span><span class="o">></span><span class="w"> </span><span class="n">p12_org</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="kt">int</span><span class="p">(</span><span class="mi">3</span><span class="p">));</span>
<span class="w"> </span><span class="n"><a href="../weak_ptr.html">std::weak_ptr</a></span><span class="o"><</span><span class="kt">int</span><span class="o">></span><span class="w"> </span><span class="n">w12</span><span class="p">(</span><span class="n">p12_org</span><span class="p">);</span>
<span class="w"> </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n"><a href="../shared_ptr.html">std::shared_ptr</a></span><span class="o"><</span><span class="kt">int</span><span class="o">></span><span class="w"> </span><span class="n">p12</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">w12</span><span class="p">.</span><span class="n"><a href="../weak_ptr/lock.html">lock()</a></span><span class="p">)</span><span class="w"> </span><span class="p">{</span>
<span class="w"> </span><span class="n"><a href="../../cassert/assert.html">assert</a></span><span class="p">(</span><span class="o">*</span><span class="n">p12</span><span class="p">.</span><span class="n"><a href="get.html">get()</a></span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="mi">3</span><span class="p">);</span>
<span class="w"> </span><span class="n"><a href="../../cassert/assert.html">assert</a></span><span class="p">(</span><span class="n">p12</span><span class="p">.</span><span class="n"><a href="use_count.html">use_count()</a></span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="mi">2</span><span class="p">);</span>
<span class="w"> </span><span class="p">}</span>
<span class="w"> </span><span class="k">else</span><span class="w"> </span><span class="p">{</span>
<span class="w"> </span><span class="n"><a href="../../cassert/assert.html">assert</a></span><span class="p">(</span><span class="nb">false</span><span class="p">);</span>
<span class="w"> </span><span class="p">}</span>
<span class="w"> </span><span class="c1">// (14)</span>
<span class="w"> </span><span class="c1">// unique_ptrからリソースを移動する</span>
<span class="w"> </span><span class="n"><a href="../unique_ptr.html">std::unique_ptr</a></span><span class="o"><</span><span class="kt">int</span><span class="o">></span><span class="w"> </span><span class="n">p14_org</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="kt">int</span><span class="p">(</span><span class="mi">3</span><span class="p">));</span>
<span class="w"> </span><span class="n"><a href="../shared_ptr.html">std::shared_ptr</a></span><span class="o"><</span><span class="kt">int</span><span class="o">></span><span class="w"> </span><span class="n">p14</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n"><a href="../../utility/move.html">std::move</a></span><span class="p">(</span><span class="n">p14_org</span><span class="p">);</span>
<span class="w"> </span><span class="n"><a href="../../cassert/assert.html">assert</a></span><span class="p">(</span><span class="o">*</span><span class="n">p14</span><span class="p">.</span><span class="n"><a href="get.html">get()</a></span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="mi">3</span><span class="p">);</span>
<span class="w"> </span><span class="n"><a href="../../cassert/assert.html">assert</a></span><span class="p">(</span><span class="n">p14</span><span class="p">.</span><span class="n"><a href="use_count.html">use_count()</a></span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="mi">1</span><span class="p">);</span>
<span class="w"> </span><span class="n"><a href="../../cassert/assert.html">assert</a></span><span class="p">(</span><span class="n">p14_org</span><span class="p">.</span><span class="n"><a href="get.html">get()</a></span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="nb">nullptr</span><span class="p">);</span>
<span class="w"> </span><span class="c1">// (15)</span>
<span class="w"> </span><span class="c1">// 空のshared_ptrを構築する</span>
<span class="w"> </span><span class="n"><a href="../shared_ptr.html">std::shared_ptr</a></span><span class="o"><</span><span class="kt">int</span><span class="o">></span><span class="w"> </span><span class="n">p15</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nb">nullptr</span><span class="p">;</span>
<span class="w"> </span><span class="n"><a href="../../cassert/assert.html">assert</a></span><span class="p">(</span><span class="n">p15</span><span class="p">.</span><span class="n"><a href="get.html">get()</a></span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="nb">nullptr</span><span class="p">);</span>
<span class="w"> </span><span class="n"><a href="../../cassert/assert.html">assert</a></span><span class="p">(</span><span class="n">p15</span><span class="p">.</span><span class="n"><a href="use_count.html">use_count()</a></span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="mi">0</span><span class="p">);</span>
<span class="p">}</span>
</code></pre></div>
</div></p>
<h4>出力</h4>
<p><pre><code></code></pre></p>
<h3>エイリアシングコンストラクタで所有権を共有する</h3>
<p>エイリアシングコンストラクタ(7), (16)は、所有権はもとの<code>shared_ptr</code>オブジェクトと共有したまま、保持するポインタだけを別のものに差し替える。これによって、オブジェクトのメンバ変数を指す<code>shared_ptr</code>オブジェクトを作りつつ、そのメンバ変数を含むオブジェクト全体の寿命を、メンバ変数を参照している間だけ延ばせる。</p>
<p><div class="yata" id="aeea5eb56732373f2f78659358ab9977b87216cb"><div class="codehilite"><pre><span></span><code><span class="cp">#include <a href="../../cassert.html"><cassert></a></span>
<span class="cp">#include <a href="../../memory.html"><memory></a></span>
<span class="cp">#include <a href="../../string.html"><string></a></span>
<span class="cp">#include <a href="../../utility.html"><utility></a></span>
<span class="k">struct</span><span class="w"> </span><span class="nc">Person</span><span class="w"> </span><span class="p">{</span>
<span class="w"> </span><span class="n"><a href="../../string/basic_string.html">std::string</a></span><span class="w"> </span><span class="n">name</span><span class="p">;</span>
<span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">age</span><span class="p">;</span>
<span class="p">};</span>
<span class="kt">int</span><span class="w"> </span><span class="nf">main</span><span class="p">()</span>
<span class="p">{</span>
<span class="w"> </span><span class="n"><a href="../shared_ptr.html">std::shared_ptr</a></span><span class="o"><</span><span class="n"><a href="../../string/basic_string.html">std::string</a></span><span class="o">></span><span class="w"> </span><span class="n">name</span><span class="p">;</span>
<span class="w"> </span><span class="p">{</span>
<span class="w"> </span><span class="n"><a href="../shared_ptr.html">std::shared_ptr</a></span><span class="o"><</span><span class="n">Person</span><span class="o">></span><span class="w"> </span><span class="n">person</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">Person</span><span class="p">{</span><span class="s">"Alice"</span><span class="p">,</span><span class="w"> </span><span class="mi">25</span><span class="p">});</span>
<span class="w"> </span><span class="c1">// (7)</span>
<span class="w"> </span><span class="c1">// personと所有権を共有しつつ、メンバ変数nameを指すshared_ptrオブジェクトを構築する</span>
<span class="w"> </span><span class="n">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n"><a href="../shared_ptr.html">std::shared_ptr</a></span><span class="o"><</span><span class="n"><a href="../../string/basic_string.html">std::string</a></span><span class="o">></span><span class="p">(</span><span class="n">person</span><span class="p">,</span><span class="w"> </span><span class="o">&</span><span class="n">person</span><span class="o">-></span><span class="n">name</span><span class="p">);</span>
<span class="w"> </span><span class="n"><a href="../../cassert/assert.html">assert</a></span><span class="p">(</span><span class="n">name</span><span class="p">.</span><span class="n"><a href="use_count.html">use_count()</a></span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="mi">2</span><span class="p">);</span>
<span class="w"> </span><span class="n"><a href="../../cassert/assert.html">assert</a></span><span class="p">(</span><span class="o">*</span><span class="n">name</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="s">"Alice"</span><span class="p">);</span>
<span class="w"> </span><span class="p">}</span>
<span class="w"> </span><span class="c1">// personは破棄されたが、nameが所有権をもっているため、</span>
<span class="w"> </span><span class="c1">// Personオブジェクト全体がまだ破棄されていない</span>
<span class="w"> </span><span class="n"><a href="../../cassert/assert.html">assert</a></span><span class="p">(</span><span class="n">name</span><span class="p">.</span><span class="n"><a href="use_count.html">use_count()</a></span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="mi">1</span><span class="p">);</span>
<span class="w"> </span><span class="n"><a href="../../cassert/assert.html">assert</a></span><span class="p">(</span><span class="o">*</span><span class="n">name</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="s">"Alice"</span><span class="p">);</span>
<span class="w"> </span><span class="c1">// (16)</span>
<span class="w"> </span><span class="c1">// 所有権を移動しつつ、メンバ変数ageを指すshared_ptrオブジェクトを構築する。</span>
<span class="w"> </span><span class="c1">// 所有権の移動はコンストラクタの中で行われるため、</span>
<span class="w"> </span><span class="c1">// 実引数&person->ageの評価は移動の影響を受けない</span>
<span class="w"> </span><span class="n"><a href="../shared_ptr.html">std::shared_ptr</a></span><span class="o"><</span><span class="n">Person</span><span class="o">></span><span class="w"> </span><span class="n">person</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">Person</span><span class="p">{</span><span class="s">"Bob"</span><span class="p">,</span><span class="w"> </span><span class="mi">30</span><span class="p">});</span>
<span class="w"> </span><span class="n"><a href="../shared_ptr.html">std::shared_ptr</a></span><span class="o"><</span><span class="kt">int</span><span class="o">></span><span class="w"> </span><span class="n">age</span><span class="p">(</span><span class="n"><a href="../../utility/move.html">std::move</a></span><span class="p">(</span><span class="n">person</span><span class="p">),</span><span class="w"> </span><span class="o">&</span><span class="n">person</span><span class="o">-></span><span class="n">age</span><span class="p">);</span>
<span class="w"> </span><span class="n"><a href="../../cassert/assert.html">assert</a></span><span class="p">(</span><span class="n">person</span><span class="p">.</span><span class="n"><a href="use_count.html">use_count()</a></span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="mi">0</span><span class="p">);</span>
<span class="w"> </span><span class="n"><a href="../../cassert/assert.html">assert</a></span><span class="p">(</span><span class="n">person</span><span class="p">.</span><span class="n"><a href="get.html">get()</a></span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="nb">nullptr</span><span class="p">);</span>
<span class="w"> </span><span class="n"><a href="../../cassert/assert.html">assert</a></span><span class="p">(</span><span class="o">*</span><span class="n">age</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="mi">30</span><span class="p">);</span>
<span class="p">}</span>
</code></pre></div>
</div></p>
<h4>出力</h4>
<p><pre><code></code></pre></p>
<h2>バージョン</h2>
<h3>言語</h3>
<ul>
<li>C++11</li>
</ul>
<h3>処理系</h3>
<ul>
<li><a href="../../../implementation.html#clang">Clang</a>: 3.0 <span aria-label="検証済" role="img" title="検証済">✅</span></li>
<li><a href="../../../implementation.html#gcc">GCC</a>: 4.3.6 (unique_ptr <span aria-label="検証済" role="img" title="検証済">✅</span>, nullptr以外) <span aria-label="検証済" role="img" title="検証済">✅</span>, 4.4.7 (nullptr以外) <span aria-label="検証済" role="img" title="検証済">✅</span>, 4.6.4 <span aria-label="検証済" role="img" title="検証済">✅</span></li>
<li><a href="../../../implementation.html#visual_cpp">Visual C++</a>: 2008 (TR1) <span aria-label="検証済" role="img" title="検証済">✅</span>, 2010 <span aria-label="検証済" role="img" title="検証済">✅</span>, 2012 <span aria-label="検証済" role="img" title="検証済">✅</span>, 2013 <span aria-label="検証済" role="img" title="検証済">✅</span><ul>
<li>2008は(1), (2), (3), (4), (8), (9), (12), (13)のみ</li>
<li>2008, 2010の(13)は、仮引数の型が<code>auto_ptr<Y>&&</code>ではなく<code>auto_ptr<Y>&</code>になっている。</li>
</ul>
</li>
</ul>
<h2>参照</h2>
<ul>
<li>(4), (5) : <a href="http://d.hatena.ne.jp/yohhoy/20120623/p1" target="_blank">nullptrを所有するshared_ptr - yohhoyの日記</a></li>
<li>(7) : <a href="http://d.hatena.ne.jp/gintenlabo/20091214/1260804379" target="_blank">今更ながらに Boost.SmartPointers を考える - 野良C++erの雑記帳</a></li>
<li><a href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2007/n2351.htm" target="_blank">N2351 Improving shared_ptr for C++0x, Revision 2</a><ul>
<li>(7)の経緯となる提案文書</li>
</ul>
</li>
<li><a href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2007/n2435.htm" target="_blank">N2435 Explicit bool for Smart Pointers</a><ul>
<li>(15)の経緯となる提案文書</li>
</ul>
</li>
<li><a href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2014/n4190.htm" target="_blank">N4190 Removing <code>auto_ptr</code>, <code>random_shuffle()</code>, And Old <code><functional></code> Stuff</a></li>
<li><a href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2016/p0414r1.html" target="_blank">P0414R1 Merging <code>shared_ptr</code> changes from Library Fundamentals to C++17</a></li>
<li><a href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2016/p0497r0.html" target="_blank">P0497R0 Fixes to <code>shared_ptr</code> support for arrays</a></li>
<li><a href="https://cplusplus.github.io/LWG/issue758" target="_blank">LWG Issue 758. <code>shared_ptr</code> and <code>nullptr</code></a><ul>
<li>C++11で、削除子(とアロケータ)を<code>nullptr</code>とともに渡す<a class="cpprefjp-defined-word" data-desc="同名の関数を異なる引数・テンプレート・制約などで複数定義すること。または同名の関数の集合">オーバーロード</a>が追加された。<code>Y*</code>をとる<a class="cpprefjp-defined-word" data-desc="同名の関数を異なる引数・テンプレート・制約などで複数定義すること。または同名の関数の集合">オーバーロード</a>では<code>nullptr</code>から<code>Y</code>を推論できないため、削除子付きの空の<code>shared_ptr</code>を構築できなかった</li>
</ul>
</li>
<li><a href="https://cplusplus.github.io/LWG/issue881" target="_blank">LWG Issue 881. <code>shared_ptr</code> conversion issue</a><ul>
<li>C++11で、(11)のムーブコンストラクタの<code>Y*</code>から<code>T*</code>への変換可能性が、単なる要件から<a class="cpprefjp-defined-word" data-desc="関数呼び出し時に、同名の関数の中から実際に呼び出す関数を決定する処理。このときの候補になることを、オーバーロード解決に参加するという">オーバーロード解決</a>に参加する条件へ改められた</li>
</ul>
</li>
<li><a href="https://cplusplus.github.io/LWG/issue925" target="_blank">LWG Issue 925. <code>shared_ptr</code>'s explicit conversion from <code>unique_ptr</code></a><ul>
<li>C++11で、<code><a href="../unique_ptr.html">unique_ptr</a></code>および<code>auto_ptr</code>から構築するコンストラクタの<code>explicit</code>指定が外された。これらからの所有権の移動は安全であり、暗黙変換を禁止する理由がなかったため</li>
</ul>
</li>
<li><a href="https://cplusplus.github.io/LWG/issue1402" target="_blank">LWG Issue 1402. <code>nullptr</code> constructors for smart pointers should be <code>constexpr</code></a><ul>
<li>C++11で、<code><a href="../../cstddef/nullptr_t.html">nullptr</a></code>からのコンストラクタに<code>constexpr</code>が付加された。デフォルトコンストラクタと同様に、静的初期化できるようにするため</li>
</ul>
</li>
<li><a href="https://wg21.cmeerw.net/lwg/issue2365" target="_blank">LWG Issue 2365. Missing <code>noexcept</code> in <code>shared_ptr::shared_ptr(nullptr_t)</code></a></li>
<li><a href="https://cplusplus.github.io/LWG/issue2685" target="_blank">LWG Issue 2685. <code>shared_ptr</code> deleters must not throw on move construction</a><ul>
<li>C++17で、削除子<code>D</code>の構築(<code>CopyConstructible</code>は維持)が<a class="cpprefjp-defined-word" data-desc="問題が発生したときに、現在実行位置を過去に通過・記録した位置に戻し、文脈情報を添えて紐づけられた処理(例外ハンドラー)を呼び出す仕組み。またはその事態">例外</a>を投げないという要件が追加された</li>
</ul>
</li>
<li><a href="https://cplusplus.github.io/LWG/issue2802" target="_blank">LWG Issue 2802. <code>shared_ptr</code> constructor requirements for a deleter</a><ul>
<li>C++17で、削除子<code>D</code>の要件が<code>CopyConstructible</code>から<code>MoveConstructible</code>に緩和され、<code>d</code>および<code>std::move(d)</code>からの構築が<a class="cpprefjp-defined-word" data-desc="問題が発生したときに、現在実行位置を過去に通過・記録した位置に戻し、文脈情報を添えて紐づけられた処理(例外ハンドラー)を呼び出す仕組み。またはその事態">例外</a>を投げないこと、<code>d(p)</code>が<a class="cpprefjp-defined-word" data-desc="プログラムが文法規則・診断対象の意味規則・単一定義規則を満たすこと" href="../../../implementation-compliance.html#dfn-well-formed">適格</a>であり定義された動作をし、<a class="cpprefjp-defined-word" data-desc="問題が発生したときに、現在実行位置を過去に通過・記録した位置に戻し、文脈情報を添えて紐づけられた処理(例外ハンドラー)を呼び出す仕組み。またはその事態">例外</a>を投げないことが規定された。あわせて「<code>D</code>のデストラクタが<a class="cpprefjp-defined-word" data-desc="問題が発生したときに、現在実行位置を過去に通過・記録した位置に戻し、文脈情報を添えて紐づけられた処理(例外ハンドラー)を呼び出す仕組み。またはその事態">例外</a>を投げない」要件は削除された</li>
</ul>
</li>
<li><a href="https://open-std.org/jtc1/sc22/wg21/docs/papers/2025/p3037r6.pdf" target="_blank">P3037R6 <code>constexpr std::shared_ptr</code> and friends</a></li>
<li><a href="https://cplusplus.github.io/LWG/issue2874" target="_blank">LWG Issue 2874. Constructor <code>shared_ptr::shared_ptr(Y*)</code> should be constrained</a><ul>
<li>C++17で、ポインタから構築するコンストラクタが、<code>delete p</code>(配列版は<code>delete[] p</code>)が妥当で<code>Y*</code>が<code>T*</code>と互換な場合のみ<a class="cpprefjp-defined-word" data-desc="関数呼び出し時に、同名の関数の中から実際に呼び出す関数を決定する処理。このときの候補になることを、オーバーロード解決に参加するという">オーバーロード解決</a>に参加するよう制約化された</li>
</ul>
</li>
<li><a href="https://cplusplus.github.io/LWG/issue2875" target="_blank">LWG Issue 2875. <code>shared_ptr::shared_ptr(Y* | D | […])</code> constructors should be constrained</a><ul>
<li>C++17で、削除子を取るコンストラクタが、<code>D</code>がムーブ構築可能で<code>d(p)</code>が妥当などの条件を満たす場合のみ<a class="cpprefjp-defined-word" data-desc="関数呼び出し時に、同名の関数の中から実際に呼び出す関数を決定する処理。このときの候補になることを、オーバーロード解決に参加するという">オーバーロード解決</a>に参加するよう制約化された</li>
</ul>
</li>
<li><a href="https://cplusplus.github.io/LWG/issue2876" target="_blank">LWG Issue 2876. <code>shared_ptr::shared_ptr(const weak_ptr<Y>&)</code> constructor should be constrained</a><ul>
<li>C++17で、<code>weak_ptr</code>から構築するコンストラクタ(12)が、<code>Y*</code>が<code>T*</code>と互換な場合のみ<a class="cpprefjp-defined-word" data-desc="関数呼び出し時に、同名の関数の中から実際に呼び出す関数を決定する処理。このときの候補になることを、オーバーロード解決に参加するという">オーバーロード解決</a>に参加するよう制約化され、<code>is_constructible</code>が正しい結果を返すようになった</li>
</ul>
</li>
<li><a href="https://wg21.cmeerw.net/lwg/issue2996" target="_blank">LWG Issue 2996. Missing rvalue overloads for <code>shared_ptr</code> operations</a></li>
</ul></div>
</div>
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