{"id":326728,"date":"2021-02-07T05:25:00","date_gmt":"2021-02-06T21:25:00","guid":{"rendered":"http:\/\/4563.org\/?p=326728"},"modified":"2021-02-07T05:25:00","modified_gmt":"2021-02-06T21:25:00","slug":"c%e7%9a%84%e7%bc%ba%e7%9c%81%e6%8b%b7%e8%b4%9d%e6%9e%84%e9%80%a0%e5%92%8c%e6%b5%85%e6%8b%b7%e8%b4%9d%e6%9c%89%e6%b2%a1%e6%9c%89%e5%8c%ba%e5%88%ab%ef%bc%9f","status":"publish","type":"post","link":"http:\/\/4563.org\/?p=326728","title":{"rendered":"C++\u7684\u7f3a\u7701\u62f7\u8d1d\u6784\u9020\u548c\u6d45\u62f7\u8d1d\u6709\u6ca1\u6709\u533a\u522b\uff1f"},"content":{"rendered":"
\n
\n
\n

C++\u7684\u7f3a\u7701\u62f7\u8d1d\u6784\u9020\u548c\u6d45\u62f7\u8d1d\u6709\u6ca1\u6709\u533a\u522b\uff1f <\/h1>\n

<\/p>\n

\n
\u8cc7\u6df1\u5927\u4f6c : James369 <\/span> <\/i> 1<\/span> <\/div>\n
<\/div>\n<\/p><\/div>\n<\/p><\/div>\n<\/p><\/div>\n
<\/p>\n

\u6bd4\u5982\u4e00\u4e2a\u7c7b\uff1a<\/p>\n

class Test { public:     std::string s;    \/\/s \u5728\u6d45\u62f7\u8d1d\u7684\u65f6\u5019\uff0c\u662f\u5426\u4f1a\u8c03\u7528 std::string \u7684\u62f7\u8d1d\u6784\u9020\uff1f     float a; }  std::shared_ptr<Test> function() {     ...     auto test = Test();  \/\/\u6808\u4e0a\u521b\u5efa     test.s = \"aaa\";         test.a = 111;     auto result = std::make_shared<Test>(test);  \/\/\u8c03\u7528 Test \u7f3a\u7701\u6784\u9020\u51fd\u6570\uff0c\u5373 memcpy?     return result; }  int main() {     auto ret = function();     ... }  <\/code><\/pre>\n
\u6b64\u65f6\u53d1\u751f\u6d45\u62f7\u8d1d\uff0c\u5982\u679c\u76f4\u63a5 memcpy \u8986\u76d6\u8fc7\u53bb\uff0c\u90a3\u4e48\u6210\u5458\u53d8\u91cf s \u6307\u5411\u7684\u5b57\u7b26\u4e32\u7684\u5185\u5bb9\u662f\u6808\u4e0a\u7684\uff0c\u79bb\u5f00\u6808\u5c31\u4f1a\u53d1\u751f\u5185\u5b58\u8bbf\u95ee\u9519\u8bef\u3002\u4f46\u5b9e\u9645\u6d4b\u8bd5\u5e76\u6ca1\u6709\u53d1\u751f\u5185\u5b58\u9519\u8bef\u3002<\/p>\n<\/p><\/div>\n
 \u5927\u4f6c\u6709\u8a71\u8aaa<\/b> (15<\/span>)        <\/div>\n
 <\/div>\n<\/p><\/div>\n<\/p><\/div>\n
    \n
  • \n
    \n
    \n
     \u8cc7\u6df1\u5927\u4f6c : norz <\/span>  <\/div>\n
     <\/i>            <\/span> <\/div>\n<\/p><\/div>\n
                                                                 string \u7684\u62f7\u8d1d\u6784\u9020\u4f1a\u6267\u884c                                                            <\/div>\n<\/p><\/div>\n<\/li>\n
  • \n
    \n
    \n
     \u8cc7\u6df1\u5927\u4f6c : auto8888 <\/span>  <\/div>\n
     <\/i>            <\/span> <\/div>\n<\/p><\/div>\n
                                                                 string \u4e0d\u662f\u6307\u9488\u6210\u5458\u5462\uff0c\u4eb2\u4eb2\u3002                                                            <\/div>\n<\/p><\/div>\n<\/li>\n
  • \n
    \n
    \n
     \u8cc7\u6df1\u5927\u4f6c : norz <\/span>  <\/div>\n
     <\/i>            <\/span> <\/div>\n<\/p><\/div>\n
                                                                 \u6d45\u62f7\u8d1d\u5e76\u4e0d\u662f memcpy\uff0c\u800c\u662f\u76f4\u63a5\u8d4b\u503c                                                            <\/div>\n<\/p><\/div>\n<\/li>\n
  • \n
    \n
    \n
     \u8cc7\u6df1\u5927\u4f6c : owwlo <\/span>  <\/div>\n
     <\/i>            <\/span> <\/div>\n<\/p><\/div>\n
                                                                 \u50cf\u4e0a\u8bf4\u7684\uff0c\u9ed8\u8ba4\u662f\u62f7\u8d1d\u6784\u9020\u51fd\u6570\u5e76\u4e0d\u4f1a\u662f memcpy\uff0c\u5373\u4f7f\u662f\u7f16\u8bd1\u5668\u4f18\u5316\uff0c\u6211\u201c\u731c\u201d\u7f16\u8bd1\u5668\u4e5f\u53ea\u4f1a\u5bf9 std:: is_trivially_copyable \u7684\u7ed3\u6784\u6267\u884c memcpy \u3002                                                            <\/div>\n<\/p><\/div>\n<\/li>\n
  • \n
    \n
    \n
     \u4e3b<\/span> \u8cc7\u6df1\u5927\u4f6c : James369 <\/span>  <\/div>\n
     <\/i>            <\/span> <\/div>\n<\/p><\/div>\n
                                                                 @norz \u5982\u679c\u662f\u8fd9\u6837\uff0c\u90a3\u4e48\u6d45\u62f7\u8d1d\u5c31\u4e0d\u662f\u7b80\u5355\u7684 memcpy \u7684\u4e8c\u8fdb\u5236\u590d\u5236\u4e86\uff1f                                                            <\/div>\n<\/p><\/div>\n<\/li>\n
  • \n
    \n
    \n
     \u8cc7\u6df1\u5927\u4f6c : freemon <\/span>  <\/div>\n
     <\/i>            <\/span> <\/div>\n<\/p><\/div>\n
                                                                 stl::string \u62bd\u8c61\u51fa\u6765\u7684\u4ee3\u7801\u4e0d\u662f\u8fd9\u6837\u5417                                                            <\/div>\n<\/p><\/div>\n<\/li>\n
  • \n
    \n
    \n
     \u8cc7\u6df1\u5927\u4f6c : freemon <\/span>  <\/div>\n
     <\/i>            <\/span> <\/div>\n<\/p><\/div>\n
                                                                 class string { 
     enum { _BUF_SIZE = 16 }; 
     union _Bxty { 
     \/\/ storage for small buffer or pointer to larger one 
     char _Buf[_BUF_SIZE]; 
     char* _Ptr; 
     } _Bx; 
     size_t _Mysize; \/\/ current length of string 
     size_t _Myres; \/\/ current storage reserved for string 
    };                                                            <\/div>\n<\/p><\/div>\n<\/li>\n
  • \n
    \n
    \n
     \u8cc7\u6df1\u5927\u4f6c : levelworm <\/span>  <\/div>\n
     <\/i>            <\/span> <\/div>\n<\/p><\/div>\n
                                                                 \u6d45\u62f7\u8d1d\u5c31\u662f\u4e00\u4e2a\u4e2a bit \u590d\u5236\u8fc7\u53bb\u5427\uff1f\u7c7b\u91cc\u5e26\u6307\u9488\u9700\u8981\u5728\u5806\u4e0a\u521b\u5efa\u5bf9\u8c61\u7684\u5fc5\u987b\u7528\u6df1\u62f7\u8d1d\u3002                                                            <\/div>\n<\/p><\/div>\n<\/li>\n
  • \n
    \n
    \n
     \u8cc7\u6df1\u5927\u4f6c : auto8888 <\/span>  <\/div>\n
     <\/i>            <\/span> <\/div>\n<\/p><\/div>\n
                                                                 “aaa” \u5b58\u50a8\u5728\u6587\u5b57\u5e38\u91cf\u533a                                                            <\/div>\n<\/p><\/div>\n<\/li>\n
  • \n
    \n
    \n
     \u8cc7\u6df1\u5927\u4f6c : hitmanx <\/span>  <\/div>\n
     <\/i>            <\/span> <\/div>\n<\/p><\/div>\n
                                                                 string \u4e0d\u662f const char*\uff0c\u5b83\u662f\u628a\u5b57\u7b26\u4e32\u5b58\u5728 heap \u91cc\u7684\u3002\u4e14\u54ea\u6015\u662f const char*,\u8fd9\u4e2a\u6307\u9488\u6307\u5411\u4e5f\u662f\u6ca1\u95ee\u9898\u7684\u3002\u5c31\u50cf\u4e0a\u8bf4\u7684\uff0c”aaa”\u662f\u5728\u5e38\u91cf\u533a\u7684\uff0c\u800c\u4e0d\u662f\u6ce8\u91ca\u91cc\u5199\u7684\u5728\u6808\u4e0a                                                            <\/div>\n<\/p><\/div>\n<\/li>\n
  • \n
    \n
    \n
     \u8cc7\u6df1\u5927\u4f6c : amaranthf <\/span>  <\/div>\n
     <\/i>            <\/span> <\/div>\n<\/p><\/div>\n
                                                                 \u6d45\u62f7\u8d1d\uff0c\u6307\u7684\u662f\u4e00\u79cd\u201c\u53d8\u91cf\u95f4\u8d4b\u503c\u7684\u65b9\u5f0f\u201d\uff0c\u800c\u201cclass \u7684\u9ed8\u8ba4\u590d\u5236\u6784\u9020\u5e76\u975e\u6d45\u62f7\u8d1d\u201d\u3002
    class \u7684\u9ed8\u8ba4\u590d\u5236\u6784\u9020\u51fd\u6570\u4e2d\uff0c\u53ea\u6709\u5bf9\u6307\u9488\u6210\u5458\u624d\u4f1a\u8fdb\u884c\u6d45\u62f7\u8d1d\uff0c\u5373\u76f4\u63a5\u8d4b\u503c\uff0c\u5bf9\u5bf9\u8c61\u7c7b\u578b\u7684\u6210\u5458\u4f1a\u6267\u884c\u5176\u9ed8\u8ba4\u590d\u5236\u6784\u9020\u3002                                                            <\/div>\n<\/p><\/div>\n<\/li>\n
  • \n
    \n
    \n
     \u8cc7\u6df1\u5927\u4f6c : alazysun <\/span>  <\/div>\n
     <\/i>            <\/span> <\/div>\n<\/p><\/div>\n
                                                                 \u7f3a\u7701\u7684\u62f7\u8d1d\u6784\u9020\u5c31\u662f\u6d45\u62f7\u8d1d\uff0c\u4f46\u5bf9\u6709\u62f7\u8d1d\u6784\u9020\u51fd\u6570\u7684\u6210\u5458\uff0c\u5219\u4f1a\u8c03\u7528\u5b83\u7684\u62f7\u8d1d\u6784\u9020\u3002                                                            <\/div>\n<\/p><\/div>\n<\/li>\n
  • \n
    \n
    \n
     \u8cc7\u6df1\u5927\u4f6c : lvzx <\/span>  <\/div>\n
     <\/i>            <\/span> <\/div>\n<\/p><\/div>\n
                                                                 \u4f60\u81ea\u5df1\u5199\u4e2a\u7c7b\uff0c\u62f7\u8d1d\u6784\u9020\u52a0\u70b9\u6253\u5370\u4e0d\u5c31\u77e5\u9053\u4e86\uff1f\u81ea\u52a8\u751f\u6210\u7684\u62f7\u8d1d\u6784\u9020\u51fd\u6570\uff0c\u4f1a\u8c03\u7528\u6210\u5458\u53d8\u91cf\u7684\u62f7\u8d1d\u6784\u9020\u51fd\u6570\uff0c\u6240\u4ee5 string \u5f53\u7136\u4e0d\u4f1a\u6709\u95ee\u9898                                                            <\/div>\n<\/p><\/div>\n<\/li>\n
  • \n
    \n
    \n
     \u8cc7\u6df1\u5927\u4f6c : xuanbg <\/span>  <\/div>\n
     <\/i>            <\/span> <\/div>\n<\/p><\/div>\n
                                                                 \u6d45\u62f7\u8d1d\u53ea\u662f\u590d\u5236\u6307\u9488\uff0c\u6df1\u62f7\u8d1d\u662f\u590d\u5236\u6570\u636e+\u65b0\u7684\u6307\u9488\u3002                                                            <\/div>\n<\/p><\/div>\n<\/li>\n
  • \n
    \n
    \n
     \u8cc7\u6df1\u5927\u4f6c : walker522 <\/span>  <\/div>\n
     <\/i>            <\/span> <\/div>\n<\/p><\/div>\n
                                                                 \u6df1\u6d45\u62f7\u8d1d\u662f\u76f8\u5bf9\u4e8e\u80fd\u5426\u7ea7\u8054\u590d\u5236\u6307\u9488\u6240\u6307\u5185\u5bb9\u7684\uff0c\u662f\u7c7b\u578b\u7684\u62f7\u8d1d\u51fd\u6570\u8bbe\u8ba1\u95ee\u9898\u3002
    \u800c\u6b63\u786e\u8bbe\u8ba1\u7684\u5bf9\u8c61\u548c\u57fa\u672c\u7c7b\u578b\u662f\u53ef\u4ee5\u81ea\u52a8\u7ea7\u8054\u590d\u5236\u3002
    make_shared \u5148\u5728\u5806\u4e0a\u5206\u914d\u5185\u5b58\uff0c\u518d\u6267\u884c\u5bf9\u8c61\u62f7\u8d1d\u3002
    string \u62f7\u8d1d\u5185\u90e8\u4f1a\u8fdb\u884c\u4e86\u6307\u9488\u5185\u5bb9\u62f7\u8d1d\uff0c\u662f\u6df1\u62f7\u8d1d\u3002                                                            <\/div>\n<\/p><\/div>\n<\/li>\n
  • \n","protected":false},"excerpt":{"rendered":"
    C++\u7684\u7f3a\u7701\u62f7\u8d1d\u6784\u9020\u548c\u6d45\u62f7\u8d1d\u6709\u6ca1\u6709…<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":[],"categories":[],"tags":[],"_links":{"self":[{"href":"http:\/\/4563.org\/index.php?rest_route=\/wp\/v2\/posts\/326728"}],"collection":[{"href":"http:\/\/4563.org\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"http:\/\/4563.org\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"http:\/\/4563.org\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"http:\/\/4563.org\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=326728"}],"version-history":[{"count":0,"href":"http:\/\/4563.org\/index.php?rest_route=\/wp\/v2\/posts\/326728\/revisions"}],"wp:attachment":[{"href":"http:\/\/4563.org\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=326728"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"http:\/\/4563.org\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=326728"},{"taxonomy":"post_tag","embeddable":true,"href":"http:\/\/4563.org\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=326728"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}