{"id":45,"date":"2024-12-14T16:25:33","date_gmt":"2024-12-14T08:25:33","guid":{"rendered":"https:\/\/genetop.top\/?p=45"},"modified":"2024-12-14T16:27:10","modified_gmt":"2024-12-14T08:27:10","slug":"class-memory-layer","status":"publish","type":"post","link":"https:\/\/genetop.top\/index.php\/2024\/12\/14\/class-memory-layer\/","title":{"rendered":"class \u4ec0\u4e48\u65f6\u5019\u4f1a\u89e6\u53d1\u5185\u5b58\u5bf9\u9f50\uff1f"},"content":{"rendered":"

\u5728 C++ \u4e2d\uff0c\u7c7b\uff08class<\/code>\uff09\u7684\u5185\u5b58\u5bf9\u9f50<\/strong>\u4f1a\u5728\u4ee5\u4e0b\u60c5\u51b5\u4e0b\u89e6\u53d1\uff1a<\/p>\n

    \n
  1. \u7c7b\u7684\u6210\u5458\u53d8\u91cf\u7c7b\u578b\u5177\u6709\u5bf9\u9f50\u8981\u6c42<\/strong>\u3002<\/li>\n
  2. \u7c7b\u4e2d\u5305\u542b\u7ee7\u627f\u5173\u7cfb\u65f6\uff0c\u57fa\u7c7b\u4e0e\u6d3e\u751f\u7c7b\u7684\u5bf9\u9f50\u53ef\u80fd\u53d7\u5f71\u54cd<\/strong>\u3002<\/li>\n
  3. \u5185\u5b58\u5bf9\u9f50\u53d7\u67b6\u6784\uff08\u5982 32 \u4f4d\u300164 \u4f4d\uff09\u548c\u7f16\u8bd1\u5668\u7684\u5b9e\u73b0\u7b56\u7565\u5f71\u54cd<\/strong>\u3002<\/li>\n<\/ol>\n

    \u4e0b\u9762\u8be6\u7ec6\u89e3\u6790 \u4ec0\u4e48\u65f6\u5019\u4f1a\u89e6\u53d1\u5185\u5b58\u5bf9\u9f50<\/strong> \u4ee5\u53ca \u5185\u5b58\u5bf9\u9f50\u7684\u89c4\u5219<\/strong>\u3002<\/p>\n

    \n

    \u5185\u5b58\u5bf9\u9f50\u89e6\u53d1\u7684\u6761\u4ef6<\/strong><\/h2>\n

    1. \u7c7b\u7684\u6210\u5458\u53d8\u91cf\u7c7b\u578b\u7684\u5bf9\u9f50\u8981\u6c42<\/strong><\/h3>\n

    \u6bcf\u79cd\u6570\u636e\u7c7b\u578b\u90fd\u6709\u5176\u5bf9\u9f50\u8981\u6c42\uff08alignment requirements\uff09\uff0c\u7f16\u8bd1\u5668\u4f1a\u5c06\u7c7b\u7684\u6210\u5458\u53d8\u91cf\u6309\u7167\u5176\u5bf9\u9f50\u8981\u6c42\u8fdb\u884c\u6392\u5217\uff0c\u5fc5\u8981\u65f6\u586b\u5145\u5b57\u8282\uff08padding\uff09\u4ee5\u6ee1\u8db3\u5bf9\u9f50\u89c4\u5219\u3002
    \n\u5bf9\u9f50\u7684\u5173\u952e\u70b9\uff1a<\/strong><\/p>\n

      \n
    • \u6570\u636e\u7c7b\u578b\u7684\u5bf9\u9f50\u8981\u6c42\u662f\u7531\u5176\u5927\u5c0f\u51b3\u5b9a\u7684\uff0c\u4f8b\u5982\uff1a\n
        \n
      • char<\/code> \u901a\u5e38\u4e3a 1 \u5b57\u8282\u5bf9\u9f50\u3002<\/li>\n
      • int<\/code> \u901a\u5e38\u4e3a 4 \u5b57\u8282\u5bf9\u9f50\u3002<\/li>\n
      • double<\/code> \u901a\u5e38\u4e3a 8 \u5b57\u8282\u5bf9\u9f50\uff08\u5728 64 \u4f4d\u7cfb\u7edf\u4e0a\uff09\u3002<\/li>\n<\/ul>\n<\/li>\n
      • \u6210\u5458\u53d8\u91cf\u7684\u8d77\u59cb\u5730\u5740\u5fc5\u987b\u662f\u5176\u5bf9\u9f50\u8981\u6c42\u7684\u500d\u6570\u3002<\/li>\n<\/ul>\n

        \u4f8b\u5b50\uff1a<\/strong><\/p>\n

        \n
        <\/div>\n
        \n
        \n
        <\/div>\n<\/div>\n<\/div>\n
        #include<\/span> <iostream><\/span><\/span>
        \n#include<\/span> <cstddef><\/span><\/span><\/code><\/code>class<\/span> Example<\/span> {
        \nchar<\/span> a; \/\/ 1 \u5b57\u8282<\/span>
        \nint<\/span> b; \/\/ 4 \u5b57\u8282<\/span>
        \nchar<\/span> c; \/\/ 1 \u5b57\u8282<\/span>
        \n};<\/p>\n

        <\/code><\/code>int<\/span> main<\/span>()<\/span> <\/span>{
        \nstd::cout << “Size of Example: “<\/span> << sizeof<\/span>(Example) << std::endl;
        \nreturn<\/span> 0<\/span>;
        \n}<\/p>\n<\/div>\n<\/div>\n

        \u5206\u6790\uff1a<\/strong><\/p>\n

          \n
        1. char a<\/code> \u5360 1 \u5b57\u8282\u3002<\/li>\n
        2. \u63a5\u4e0b\u6765\u7684 int b<\/code> \u9700\u8981\u5bf9\u9f50\u5230 4 \u5b57\u8282\uff0c\u56e0\u6b64\u5728 char a<\/code> \u540e\u63d2\u5165 3 \u5b57\u8282\u7684\u586b\u5145\u3002<\/li>\n
        3. char c<\/code> \u5360 1 \u5b57\u8282\uff0c\u4f46\u7c7b\u7684\u5927\u5c0f\u6700\u7ec8\u9700\u8981\u6ee1\u8db3\u6700\u4e25\u683c\u7684\u6210\u5458\u5bf9\u9f50\uff08int<\/code> \u7684\u5bf9\u9f50\u662f 4 \u5b57\u8282\uff09\uff0c\u56e0\u6b64\u6dfb\u52a0\u586b\u5145\u5230\u603b\u5927\u5c0f\u4e3a 12 \u5b57\u8282\u3002<\/li>\n<\/ol>\n

          \u8f93\u51fa\u7ed3\u679c\uff1a<\/strong><\/p>\n

          \n
          <\/div>\n
          \n
          \n
          <\/div>\n<\/div>\n<\/div>\n
          Size of Example:<\/span> 12<\/span>
          \n<\/code><\/div>\n<\/div>\n
          \n

          2. \u57fa\u7c7b\u548c\u6d3e\u751f\u7c7b\u7684\u5bf9\u9f50<\/strong><\/h3>\n

          \u5f53\u7c7b\u6709\u7ee7\u627f\u5173\u7cfb\u65f6\uff0c\u57fa\u7c7b\u7684\u5bf9\u9f50\u8981\u6c42\u4f1a\u5f71\u54cd\u6d3e\u751f\u7c7b\u7684\u5185\u5b58\u5e03\u5c40\uff0c\u901a\u5e38\u6d3e\u751f\u7c7b\u7684\u8d77\u59cb\u5730\u5740\u9700\u8981\u6ee1\u8db3\u57fa\u7c7b\u7684\u5bf9\u9f50\u8981\u6c42\u3002<\/p>\n

          \u4f8b\u5b50\uff1a<\/strong><\/p>\n

          \n
          <\/div>\n
          \n
          \n
          <\/div>\n<\/div>\n<\/div>\n
          #include<\/span> <iostream><\/span><\/span>
          \n#include<\/span> <cstddef><\/span><\/span><\/code><\/code>class<\/span> Base<\/span> {
          \ndouble<\/span> d; \/\/ 8 \u5b57\u8282\u5bf9\u9f50<\/span>
          \n};<\/p>\n

          <\/code><\/code>class<\/span> Derived<\/span> : public<\/span> Base {
          \nchar<\/span> c; \/\/ 1 \u5b57\u8282<\/span>
          \n};<\/p>\n

          <\/code><\/code>int<\/span> main<\/span>()<\/span> <\/span>{
          \nstd::cout << “Size of Base: “<\/span> << sizeof<\/span>(Base) << std::endl;
          \nstd::cout << “Size of Derived: “<\/span> << sizeof<\/span>(Derived) << std::endl;
          \nreturn<\/span> 0<\/span>;
          \n}<\/p>\n<\/div>\n<\/div>\n

          \u5206\u6790\uff1a<\/strong><\/p>\n

            \n
          1. Base<\/code> \u53ea\u6709\u4e00\u4e2a double<\/code>\uff0c\u5360 8 \u5b57\u8282\u3002<\/li>\n
          2. Derived<\/code> \u9700\u8981\u6ee1\u8db3 Base<\/code> \u7684 8 \u5b57\u8282\u5bf9\u9f50\uff0c\u56e0\u6b64 char c<\/code> \u540e\u4f1a\u586b\u5145 7 \u5b57\u8282\uff0c\u4fdd\u8bc1\u6574\u4e2a Derived<\/code> \u7684\u5927\u5c0f\u662f Base<\/code> \u7684\u500d\u6570\u3002<\/li>\n<\/ol>\n

            \u8f93\u51fa\u7ed3\u679c\uff1a<\/strong><\/p>\n

            \n
            <\/div>\n
            Size of Base:<\/span> 8<\/span>
            \nSize of Derived:<\/span> 16<\/span>
            \n<\/code><\/div>\n<\/div>\n
            \n

            3. \u865a\u51fd\u6570\u8868\u6307\u9488\uff08vptr\uff09\u7684\u5bf9\u9f50<\/strong><\/h3>\n

            \u5982\u679c\u7c7b\u4e2d\u5305\u542b\u865a\u51fd\u6570\uff0c\u7f16\u8bd1\u5668\u4f1a\u4e3a\u6bcf\u4e2a\u5bf9\u8c61\u589e\u52a0\u4e00\u4e2a\u865a\u51fd\u6570\u8868\u6307\u9488\uff08vptr<\/code>\uff09\uff0c\u8fd9\u4e2a\u6307\u9488\u901a\u5e38\u9075\u5faa\u6307\u9488\u7c7b\u578b\u7684\u5bf9\u9f50\u8981\u6c42\uff08\u901a\u5e38\u662f 4 \u5b57\u8282\u6216 8 \u5b57\u8282\uff09\u3002<\/p>\n

            \u4f8b\u5b50\uff1a<\/strong><\/p>\n

            \n
            <\/div>\n
            \n
            \n
            <\/div>\n<\/div>\n<\/div>\n
            \n

            #include<\/span> <iostream><\/span><\/span><\/code><\/p>\n

            class<\/span> Base<\/span> {
            \nvirtual<\/span> void<\/span> func<\/span>()<\/span> <\/span>{}
            \n};<\/p>\n

            class<\/span> Derived<\/span> : public<\/span> Base {
            \nchar<\/span> c; \/\/ 1 \u5b57\u8282<\/span>
            \n};<\/p>\n

            int<\/span> main<\/span>()<\/span> <\/span>{
            \nstd::cout << “Size of Base: “<\/span> << sizeof<\/span>(Base) << std::endl;
            \nstd::cout << “Size of Derived: “<\/span> << sizeof<\/span>(Derived) << std::endl;
            \nreturn<\/span> 0<\/span>;
            \n}<\/p>\n<\/div>\n<\/div>\n

            \u5206\u6790\uff1a<\/strong><\/p>\n

              \n
            1. Base<\/code> \u4e2d\u6709\u865a\u51fd\u6570\uff0c\u56e0\u6b64\u5305\u542b\u4e00\u4e2a vptr<\/code> \u6307\u9488\uff0864 \u4f4d\u7cfb\u7edf\u4e0a\u5360 8 \u5b57\u8282\uff09\u3002<\/li>\n
            2. Derived<\/code> \u7ee7\u627f\u4e86\u865a\u51fd\u6570\u8868\u6307\u9488\uff0c\u540c\u65f6\u589e\u52a0\u4e86 char c<\/code>\uff0c\u56e0\u6b64\u6700\u7ec8\u5927\u5c0f\u9700\u8981\u5bf9\u9f50\u5230 8 \u5b57\u8282\u3002<\/li>\n<\/ol>\n

              \u8f93\u51fa\u7ed3\u679c\uff1a<\/strong><\/p>\n

              \n
              \n
              \n
              <\/div>\n<\/div>\n<\/div>\n
              Size of Base:<\/span> 8<\/span>
              \nSize of Derived:<\/span> 16<\/span>
              \n<\/code><\/div>\n<\/div>\n
              \n

              4. \u5bf9\u9f50\u53d7\u7c7b\u5bf9\u9f50\u5c5e\u6027\uff08alignment specifier\uff09\u5f71\u54cd<\/strong><\/h3>\n

              C++11 \u63d0\u4f9b\u4e86 alignas<\/code> \u5173\u952e\u5b57\uff0c\u53ef\u4ee5\u663e\u5f0f\u8bbe\u7f6e\u7c7b\u6216\u53d8\u91cf\u7684\u5bf9\u9f50\u8981\u6c42\u3002<\/p>\n

              \u4f8b\u5b50\uff1a<\/strong><\/p>\n

              \n
              <\/div>\n
              \n
              \n
              <\/div>\n<\/div>\n<\/div>\n
              #include<\/span> <iostream><\/span><\/span>
              \n#include<\/span> <cstddef><\/span><\/span><\/code><\/code>struct<\/span> alignas<\/span>(16<\/span>) Aligned {
              \nchar<\/span> c;
              \n};<\/p>\n

              <\/code><\/code>int<\/span> main<\/span>()<\/span> <\/span>{
              \nstd::cout << “Size of Aligned: “<\/span> << sizeof<\/span>(Aligned) << std::endl;
              \nstd::cout << “Alignment of Aligned: “<\/span> << alignof<\/span>(Aligned) << std::endl;
              \nreturn<\/span> 0<\/span>;
              \n}<\/p>\n<\/div>\n<\/div>\n

              \u8f93\u51fa\u7ed3\u679c\uff1a<\/strong><\/p>\n

              \n
              \n
              \n
              <\/div>\n<\/div>\n<\/div>\n
              Size of Aligned:<\/span> 16<\/span>
              \nAlignment of Aligned:<\/span> 16<\/span>
              \n<\/code><\/div>\n<\/div>\n
              \n

              5. \u7f16\u8bd1\u5668\u548c\u76ee\u6807\u5e73\u53f0\u5bf9\u9f50\u7b56\u7565<\/strong><\/h3>\n
                \n
              • \u81ea\u7136\u5bf9\u9f50\uff08natural alignment\uff09\uff1a<\/strong>
                \n\u5927\u591a\u6570\u7f16\u8bd1\u5668\u4f1a\u9ed8\u8ba4\u5bf9\u9f50\u5230\u6570\u636e\u7c7b\u578b\u7684\u5927\u5c0f\u500d\u6570\uff08\u5982 int<\/code> \u4e3a 4 \u5b57\u8282\u5bf9\u9f50\uff09\u3002<\/li>\n
              • \u5f3a\u5236\u5bf9\u9f50\uff08forced alignment\uff09\uff1a<\/strong>
                \n\u67d0\u4e9b\u5e73\u53f0\u53ef\u80fd\u5f3a\u5236\u5bf9\u9f50\u5230\u66f4\u5927\u7684\u500d\u6570\uff08\u5982 64 \u4f4d\u7cfb\u7edf\u53ef\u80fd\u5bf9\u9f50\u5230 8 \u5b57\u8282\uff09\u3002<\/li>\n
              • \u6570\u636e\u7ed3\u6784\u7684\u6574\u4f53\u5bf9\u9f50\uff1a<\/strong>
                \n\u7c7b\u7684\u5927\u5c0f\u4f1a\u5411\u6700\u4e25\u683c\u5bf9\u9f50\u8981\u6c42\u5bf9\u9f50\u3002<\/li>\n<\/ul>\n
                \n

                \u5982\u4f55\u67e5\u770b\u7c7b\u7684\u5185\u5b58\u5e03\u5c40<\/strong><\/h2>\n
                  \n
                1. \u4f7f\u7528 sizeof<\/code> \u67e5\u770b\u7c7b\u7684\u5927\u5c0f<\/strong>\uff1a\n
                  \n
                  \n
                  \n
                  <\/div>\n<\/div>\n<\/div>\n
                  std::cout << sizeof<\/span>(ClassName) << std::endl;
                  \n<\/code><\/div>\n<\/div>\n<\/li>\n
                2. \u4f7f\u7528 offsetof<\/code> \u67e5\u770b\u6210\u5458\u504f\u79fb<\/strong>\uff1a\n
                  \n
                  \n
                  \n
                  <\/div>\n<\/div>\n<\/div>\n
                  std::cout << offsetof<\/span>(ClassName, memberName) << std::endl;
                  \n<\/code><\/div>\n<\/div>\n<\/li>\n
                3. \u4f7f\u7528\u8c03\u8bd5\u5de5\u5177\uff08\u5982 GDB\uff09\u67e5\u770b\u5e03\u5c40<\/strong>\u3002<\/li>\n<\/ol>\n
                  \n

                  \u603b\u7ed3<\/strong><\/h3>\n
                    \n
                  • \u7c7b\u7684\u5185\u5b58\u5bf9\u9f50\u4f1a\u5728\u4ee5\u4e0b\u573a\u666f\u89e6\u53d1\uff1a<\/strong>\n
                      \n
                    1. \u6210\u5458\u53d8\u91cf\u7684\u7c7b\u578b\u6709\u5bf9\u9f50\u8981\u6c42\u3002<\/li>\n
                    2. \u7c7b\u4e2d\u5305\u542b\u7ee7\u627f\u5173\u7cfb\u3002<\/li>\n
                    3. \u7c7b\u6709\u865a\u51fd\u6570\u8868\u6307\u9488\u3002<\/li>\n
                    4. \u663e\u5f0f\u4f7f\u7528 alignas<\/code> \u8bbe\u7f6e\u5bf9\u9f50\u3002<\/li>\n<\/ol>\n<\/li>\n
                    5. \u5f71\u54cd\u5185\u5b58\u5bf9\u9f50\u7684\u56e0\u7d20\uff1a<\/strong>\n
                        \n
                      1. \u6210\u5458\u53d8\u91cf\u7684\u7c7b\u578b\u3002<\/li>\n
                      2. \u7f16\u8bd1\u5668\u5b9e\u73b0\u548c\u76ee\u6807\u5e73\u53f0\u3002<\/li>\n
                      3. \u7c7b\u7684\u7ee7\u627f\u5173\u7cfb\u548c\u865a\u51fd\u6570\u3002<\/li>\n<\/ol>\n<\/li>\n
                      4. \u4f18\u5316\u5efa\u8bae\uff1a<\/strong>\n
                          \n
                        • \u5c06\u5bf9\u9f50\u8981\u6c42\u8f83\u9ad8\u7684\u6210\u5458\u53d8\u91cf\u653e\u5728\u7c7b\u7684\u5f00\u5934\uff0c\u51cf\u5c11\u586b\u5145\u5b57\u8282\u3002<\/li>\n<\/ul>\n<\/li>\n<\/ul>\n","protected":false},"excerpt":{"rendered":"

                          \u5728 C++ \u4e2d\uff0c\u7c7b\uff08class\uff09\u7684\u5185\u5b58\u5bf9\u9f50\u4f1a\u5728\u4ee5\u4e0b\u60c5\u51b5\u4e0b\u89e6\u53d1\uff1a \u7c7b\u7684\u6210\u5458\u53d8\u91cf\u7c7b\u578b\u5177\u6709\u5bf9\u9f50\u8981\u6c42\u3002 \u7c7b\u4e2d\u5305\u542b\u7ee7\u627f\u5173 […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[4,3],"tags":[],"class_list":["post-45","post","type-post","status-publish","format-standard","hentry","category-c","category-language"],"_links":{"self":[{"href":"https:\/\/genetop.top\/index.php\/wp-json\/wp\/v2\/posts\/45","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/genetop.top\/index.php\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/genetop.top\/index.php\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/genetop.top\/index.php\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/genetop.top\/index.php\/wp-json\/wp\/v2\/comments?post=45"}],"version-history":[{"count":2,"href":"https:\/\/genetop.top\/index.php\/wp-json\/wp\/v2\/posts\/45\/revisions"}],"predecessor-version":[{"id":47,"href":"https:\/\/genetop.top\/index.php\/wp-json\/wp\/v2\/posts\/45\/revisions\/47"}],"wp:attachment":[{"href":"https:\/\/genetop.top\/index.php\/wp-json\/wp\/v2\/media?parent=45"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/genetop.top\/index.php\/wp-json\/wp\/v2\/categories?post=45"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/genetop.top\/index.php\/wp-json\/wp\/v2\/tags?post=45"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}