{"id":362032,"date":"2021-02-23T15:29:57","date_gmt":"2021-02-23T07:29:57","guid":{"rendered":"http:\/\/4563.org\/?p=362032"},"modified":"2021-03-06T13:34:42","modified_gmt":"2021-03-06T05:34:42","slug":"c-rtti-%e5%92%8c%e5%9b%9b%e7%a7%8d%e7%b1%bb%e5%9e%8b%e8%bd%ac%e6%8d%a2","status":"publish","type":"post","link":"http:\/\/4563.org\/?p=362032","title":{"rendered":"C++ RTTI \u548c\u56db\u79cd\u7c7b\u578b\u8f6c\u6362"},"content":{"rendered":"
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C++ RTTI \u548c\u56db\u79cd\u7c7b\u578b\u8f6c\u6362 <\/h1>\n

<\/p>\n

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\u8cc7\u6df1\u5927\u4f6c : yiouejv <\/span> <\/i> 3<\/span> <\/div>\n
<\/div>\n<\/p><\/div>\n<\/p><\/div>\n<\/p><\/div>\n
<\/p>\n

RTTI \u662f Run Time Type Information \u7684\u7f29\u5199\uff0c\u4ece\u5b57\u9762\u4e0a\u6765\u7406\u89e3\u5c31\u662f\u6267\u884c\u65f6\u671f\u7684\u7c7b\u578b\u4fe1\u606f\uff0c\u5176\u91cd\u8981\u4f5c\u7528\u5c31\u662f\u52a8\u6001\u5224\u522b\u6267\u884c\u65f6\u671f\u7684\u7c7b\u578b\u3002<\/p>\n

\u5e76\u4e0d\u662f\u8bf4\u8fd9\u7bc7\u6587\u7ae0\u662f RTTI\uff0c\u548c\u7528\u4e8e RTTI \u7684\u56db\u79cd\u7c7b\u578b\u8f6c\u6362\uff0c\u800c\u662f\u4ecb\u7ecd RTTI\uff0c\u518d\u4ecb\u7ecd\u4e00\u4e0b 4 \u79cd\u7c7b\u578b\u8f6c\u6362\uff0c\u56e0\u4e3a RTTI \u6709\u7528\u5230\u5176\u4e2d\u4e00\u79cd\u7c7b\u578b\u8f6c\u6362\uff0c\u6240\u4ee5\u76f8\u5f53\u4e8e\u4e24\u7bc7\u6587\u7ae0\u5199\u5728\u4e00\u8d77\u3002<\/p>\n

\u5b9e\u9645\u4e0a RTTI \u7528\u5230\u7684\u662ftypeid()<\/code> \u548c dynamic_cast()<\/code>\u3002<\/p>\n

\u4e3a\u4ec0\u4e48\u4f1a\u6709 RTTI \uff1f<\/strong><\/p>\n

C++\u662f\u4e00\u79cd\u9759\u6001\u7c7b\u578b\u8bed\u8a00\uff0c\u5176\u6570\u636e\u7c7b\u578b\u662f\u5728\u7f16\u8bd1\u671f\u5c31\u786e\u5b9a\u7684\uff0c\u4e0d\u80fd\u5728\u8fd0\u884c\u65f6\u66f4\u6539\u3002\u7136\u800c\u7531\u4e8e\u9762\u5411\u5bf9\u8c61\u7a0b\u5e8f\u8bbe\u8ba1\u4e2d\u591a\u6001\u6027\u7684\u8981\u6c42\uff0cC++\u4e2d\u7684\u6307\u9488\u6216\u5f15\u7528(Reference)\u672c\u8eab\u7684\u7c7b\u578b\uff0c\u53ef\u80fd\u4e0e\u5b83\u5b9e\u9645\u4ee3\u8868(\u6307\u5411\u6216\u5f15\u7528)\u7684\u7c7b\u578b\u5e76\u4e0d\u4e00\u81f4\u3002\u6709\u65f6\u6211\u4eec\u9700\u8981\u5c06\u4e00\u4e2a\u591a\u6001\u6307\u9488\u8f6c\u6362\u4e3a\u5176\u5b9e\u9645\u6307\u5411\u5bf9\u8c61\u7684\u7c7b\u578b\uff0c\u5c31\u9700\u8981\u77e5\u9053\u8fd0\u884c\u65f6\u7684\u7c7b\u578b\u4fe1\u606f\uff0c\u8fd9\u5c31\u4ea7\u751f\u4e86\u8fd0\u884c\u65f6\u7c7b\u578b\u8bc6\u522b\u7684\u8981\u6c42\u3002<\/p>\n

\u5b9e\u4e8b\u6c42\u662f\u5730\u8bb2\uff0cRTTI \u662f\u6709\u7528\u7684\u3002 \u4f46\u56e0\u4e3a\u4e00\u4e9b\u7406\u8bba\u4e0a\u53ca\u65b9\u6cd5\u8bba\u4e0a\u7684\u539f\u56e0\uff0c\u5b83\u7834\u574f\u4e86\u9762\u5411\u5bf9\u8c61\u7684\u7eaf\u6d01\u6027\u3002<\/p>\n

\u9996\u5148\uff0c \u5b83\u7834\u574f\u4e86\u62bd\u8c61\uff0c\u4f7f\u4e00\u4e9b\u672c\u6765\u4e0d\u5e94\u8be5\u88ab\u4f7f\u7528\u7684\u65b9\u6cd5\u548c\u5c5e\u6027\u88ab\u4e0d\u6b63\u786e\u5730\u4f7f\u7528\u3002<\/p>\n

\u5176\u6b21\uff0c\u56e0\u4e3a\u8fd0\u884c\u65f6\u7c7b\u578b\u7684\u4e0d\u786e\u5b9a\u6027\uff0c\u5b83\u628a\u7a0b\u5e8f\u53d8\u5f97\u66f4\u8106\u5f31\u3002<\/p>\n

\u7b2c\u4e09\u70b9\uff0c\u4e5f\u662f\u6700\u91cd\u8981\u7684\u4e00\u70b9\uff0c\u5b83\u4f7f\u7a0b\u5e8f\u7f3a\u4e4f\u6269\u5c55\u6027\u3002 \u5f53\u52a0\u5165\u4e86\u4e00\u4e2a\u65b0\u7684\u7c7b\u578b\u65f6\uff0c\u4f60\u4e5f\u8bb8\u9700\u8981\u4ed4\u7ec6\u9605\u8bfb\u4f60\u7684dynamic_cast<\/code>\u7684\u4ee3\u7801\uff0c\u5fc5\u8981\u65f6\u6539\u52a8\u5b83\u4eec\uff0c\u4ee5\u4fdd\u8bc1\u8fd9\u4e2a\u65b0\u7684\u7c7b\u578b\u7684\u52a0\u5165\u4e0d\u4f1a\u5bfc\u81f4\u95ee\u9898\u3002 \u800c\u5728\u8fd9\u4e2a\u8fc7\u7a0b\u4e2d\uff0c\u7f16\u8bd1\u5668\u5c06\u4e0d\u4f1a\u7ed9\u4f60\u4efb\u4f55\u5e2e\u52a9\u3002<\/p>\n

\u603b\u7684\u6765\u8bf4\uff0cRTTI \u56e0\u4e3a\u5b83\u7684\u65b9\u6cd5\u8bba\u4e0a\u7684\u4e00\u4e9b\u7f3a\u70b9\uff0c\u5b83\u5fc5\u987b\u88ab\u975e\u5e38\u8c28\u614e\u5730\u4f7f\u7528\u3002 \u4eca\u5929\u9762\u5411\u5bf9\u8c61\u8bed\u8a00\u7684\u7c7b\u578b\u7cfb\u7edf\u4e2d\u7684\u5f88\u591a\u4e1c\u897f\u5c31\u662f\u4ea7\u751f\u4e8e\u907f\u514d RTTI \u7684\u5404\u79cd\u52aa\u529b\u3002<\/p>\n

\u9996\u5148\u6211\u4eec\u6765\u4e2a\u4f8b\u5b50\u611f\u53d7\u4e00\u4e0b:<\/p>\n

#include<iostream> #include<typeinfo> using namespace std;  class Base { public:     virtual void funcA() { cout << \"Base\" << endl; } };  class Derived : public Base { public:     virtual void funcB() { cout << \"Derived\" << endl; } };  void funcC(Base* p) {     Derived* dp = dynamic_cast<Derived*>(p);     if (dp != NULL) {         dp->funcB();     }     else {         p->funcA();     } };  void funcD(Base* p) {     Derived* dp = NULL;     if (typeid(*p) == typeid(Derived))     {         dp = static_cast<Derived*>(p);         dp->funcB();     }     else {         p->funcA();     } }  int main(int argc, char const* argv[]) {     Base* p = new Derived;     cout << typeid(p).name() << endl;     cout << typeid(*p).name() << endl;     funcD(p);     funcC(p);     delete p;      Base* dp = new Base;     funcC(dp);     funcD(dp);     delete dp;     return 0; } <\/code><\/pre>\n
funcC \u662f\u7528dynamic_cast<\/code>\u7c7b\u578b\u8f6c\u6362\u662f\u5426\u6210\u529f\u6765\u8bc6\u522b\u7c7b\u578b\u7684\uff0cdynamic_cast<\/code>\u64cd\u4f5c\u7b26\u5c06\u57fa\u7c7b\u7c7b\u578b\u5bf9\u8c61\u7684\u5f15\u7528\u6216\u6307\u9488\u8f6c\u5316\u4e3a\u540c\u4e00\u7ee7\u627f\u5c42\u6b21\u4e2d\u7684\u5176\u4ed6\u7c7b\u578b\u7684\u5f15\u7528\u6216\u6307\u9488\u3002 <\/p>\n
\u5982\u679c\u7ed1\u5b9a\u5230\u5f15\u7528\u6216\u6307\u9488\u7684\u5bf9\u8c61\u4e0d\u662f\u76ee\u6807\u7c7b\u578b\u7684\u5bf9\u8c61\uff0c\u5219dynamic_cast<\/code>\u5931\u8d25\u3002
 \u5982\u679c\u8f6c\u6362\u5230\u6307\u9488\u7c7b\u578b\u7684dynamic_cast<\/code>\u5931\u8d25\uff0c\u5219dynamic_cast<\/code>\u7684\u7ed3\u679c\u662fNULL<\/code>\u503c;
 \u5982\u679c\u8f6c\u6362\u5230\u5f15\u7528\u7c7b\u578b\u7684dynamic_cast<\/code>\u5931\u8d25\uff0c \u5219\u629b\u51fa\u4e00\u4e2abad_cast<\/code>\u7c7b\u578b\u7684\u5f02\u5e38 <\/p>\n
funcD \u662f\u7528typeid<\/code>\u5224\u65ad\u57fa\u7c7b\u5730\u5740\u662f\u5426\u4e00\u81f4\u7684\u529e\u6cd5\u6765\u8bc6\u522b\u7c7b\u578b\u7684\u3002<\/p>\n
typeid<\/h3>\n
\u4e0b\u9762\u6211\u4eec\u5177\u4f53\u8bf4\u8bf4 typeid<\/code><\/p>\n
typeid<\/code>\u662f C++\u7684\u5173\u952e\u5b57\u4e4b\u4e00, \u7b49\u540c\u4e8esizeof<\/code>\u8fd9\u7c7b operator \u3002typeid \u64cd\u4f5c\u7b26\u7684\u8fd4\u56de\u7ed3\u679c\u662f\u540d\u4e3a type_info<\/code>\u7684\u6807\u51c6\u5e93\u7c7b\u578b\u7684\u5bf9\u8c61\u7684\u5f15\u7528\uff0c\u5728\u5934\u6587\u4ef6 typeinfo \u4e2d\u5b9a\u4e49\u3002 \u6709\u4e24\u79cd\u5f62\u5f0f:<\/p>\n
    \n
  1. typeid(type)<\/li>\n
  2. typeid(expression)<\/li>\n<\/ol>\n
    \u8868\u8fbe\u5f0f\u7684\u7c7b\u578b\u662f\u7c7b\u7c7b\u578b\uff0c\u4e14\u81f3\u5c11\u542b\u6709\u4e00\u4e2a\u865a\u51fd\u6570\uff0c\u5219 typeid \u64cd\u4f5c\u7b26\u8fd4\u56de\u8868\u8fbe\u5f0f\u7684\u52a8\u6001\u7c7b\u578b\uff0c\u9700\u8981\u5728\u8fd0\u884c\u65f6\u8ba1\u7b97\uff0c\u5426\u5219\u8fd4\u56de\u8868\u8fbe\u5f0f\u7684\u9759\u6001\u7c7b\u578b\uff0c\u5728\u7f16\u8bd1\u65f6\u5c31\u53ef\u4ee5\u8ba1\u7b97\u3002<\/p>\n
    C++\u6807\u51c6\u89c4\u5b9a\u4e86\u5176\u5b9e\u73b0\u5fc5\u987b\u63d0\u4f9b\u5982\u4e0b\u56db\u79cd\u64cd\u4f5c:<\/p>\n
      \n
    1. t1 == t2: \u5982\u679c\u4e24\u4e2a\u5bf9\u8c61 t1 \u548c t2 \u7c7b\u578b\u76f8\u540c\uff0c\u5219\u8fd4\u56de true;\u5426\u5219\u8fd4\u56de false<\/li>\n
    2. t1 != t2: \u5982\u679c\u4e24\u4e2a\u5bf9\u8c61 t1 \u548c t2 \u7c7b\u578b\u4e0d\u540c\uff0c\u5219\u8fd4\u56de true;\u5426\u5219\u8fd4\u56de false<\/li>\n
    3. t.name(): \u8fd4\u56de\u7c7b\u578b\u7684 c-style \u5b57\u7b26\u4e32\uff0c\u7c7b\u578b\u540d\u5b57\u7528\u7cfb\u7edf\u76f8\u5173\u7684\u65b9\u6cd5\u4ea7\u751f<\/li>\n
    4. t1.before(t2): \u8fd4\u56de\u6307\u51fa t1 \u662f\u5426\u51fa\u73b0\u5728 t2 \u4e4b\u524d \u7684 bool \u503c<\/li>\n<\/ol>\n
      type_info<\/code>\u7c7b\u63d0\u4f9b\u4e86 public \u865a\u6790\u6784\u51fd\u6570\uff0c\u4ee5\u4f7f\u7528\u6237\u80fd\u591f\u7528\u5176\u4f5c\u4e3a\u57fa\u7c7b\u3002\u5b83\u7684\u9ed8\u8ba4\u6784\u9020\u51fd\u6570\u548c\u590d\u5236\u6784\u9020\u51fd\u6570\u53ca\u8d4b\u503c\u64cd\u4f5c\u7b26\u90fd\u5b9a\u4e49\u4e3a private\uff0c\u6240\u4ee5\u4e0d\u80fd\u5b9a\u4e49\u6216\u590d\u5236 type_info \u7c7b\u578b\u7684\u5bf9\u8c61\u3002 \u7a0b\u5e8f\u4e2d\u521b\u5efa type_info \u5bf9\u8c61\u7684\u552f\u4e00\u65b9\u6cd5\u662f\u4f7f\u7528 typeid \u64cd\u4f5c\u7b26\u3002 \u7531\u6b64\u53ef\u89c1\uff0c\u5982\u679c\u628a typeid \u770b\u4f5c\u51fd\u6570\u7684\u8bdd\uff0c\u5176\u5e94\u8be5\u662f type_info \u7684\u53cb\u5143\u3002 \u8fd9\u5177\u4f53\u7531\u7f16\u8bd1\u5668\u7684\u5b9e\u73b0\u6240\u51b3\u5b9a\uff0c\u6807\u51c6\u53ea\u8981\u6c42\u5b9e\u73b0\u4e3a\u6bcf\u4e2a\u7c7b\u578b\u8fd4\u56de\u552f\u4e00\u7684\u5b57\u7b26\u4e32\u3002<\/p>\n
      \u4f8b 1: C++\u91cc\u9762\u7684 typeid \u8fd0\u7b95\u7b26\u8fd4\u56de\u503c\u662f\u4ec0\u4e48\uff1f<\/strong><\/p>\n
      \u7b54: \u5e38\u91cf\u5bf9\u8c61\u7684\u5f15\u7528\u3002<\/p>\n
      \u5982\u679c p \u662f\u57fa\u7c7b\u6307\u9488\uff0c\u5e76\u4e14\u6307\u5411\u4e00\u4e2a\u6d3e\u751f\u7c7b\u578b\u7684\u5bf9\u8c61\uff0c\u5e76\u4e14\u57fa\u7c7b\u4e2d\u6709\u865a\u51fd\u6570\uff0c\u90a3\u4e48typeid(*p)<\/code>\u8fd4\u56de p \u6240\u6307\u5411\u7684\u6d3e\u751f\u7c7b\u7c7b\u578b\uff0ctypeid(p)<\/code>\u8fd4\u56de\u57fa\u7c7b\u7c7b\u578b\u3002<\/p>\n
      RTTI \u7684\u5b9e\u73b0\u539f\u7406<\/strong>: \u901a\u8fc7\u5728\u865a\u8868\u4e2d\u653e\u4e00\u4e2a\u989d\u5916\u7684\u6307\u9488\uff0c\u6bcf\u4e2a\u65b0\u7c7b\u53ea\u4ea7\u751f\u4e00\u4e2a typeinfo \u5b9e\u4f8b\uff0c\u989d\u5916\u6307\u9488\u6307\u5411 typeinfo, typeid \u8fd4\u56de\u5bf9\u5b83\u7684\u4e00\u4e2a\u5f15\u7528\u3002<\/p>\n
      static_cast<\/h3>\n
      static_cast < new_type > ( expression ) <\/code><\/p>\n
      \u672c\u6765\u5e94\u8be5\u5148\u8ba8\u8bbadynamic_cast<\/code>\u7684\uff0c\u56e0\u4e3a\u54b1\u4eec\u672c\u6765\u804a\u7684 RTTI \u561b\uff0c\u4f46\u662f\u5148\u4e86\u89e3\u4e00\u4e0bstatic_cast<\/code>\uff0c\u7136\u540e\u770b\u548cdynamic_cast<\/code>\u7684\u6bd4\u8f83\u53ef\u80fd\u66f4\u597d\u4e00\u70b9\u3002<\/p>\n
      \u4f7f\u7528\u573a\u666f:<\/p>\n
        \n
      1. \u57fa\u672c\u6570\u636e\u7c7b\u578b\u4e4b\u95f4\u7684\u8f6c\u6362<\/li>\n
      2. initializing conversion<\/li>\n<\/ol>\n
        int n = static_cast<int>(3.14); cout << \"n = \" << n << 'n'; vector<int> v = static_cast<vector<int>>(10); cout << \"v.size() = \" << v.size() << 'n'; <\/code><\/pre>\n
          \n
        1. \u7c7b\u6307\u9488\u6216\u5f15\u7528\u5411\u4e0b\u8f6c\u6362\u3002<\/li>\n
        2. \u5c06\u7c7b\u578b\u8f6c\u4e3a\u53f3\u503c\u7c7b\u578b\uff0c\u8fdb\u884c move \u64cd\u4f5c\uff0c\u8fd9\u4e2a\u5728\u6807\u51c6\u5e93\u4e2d\u6709\u4f53\u73b0\uff08\u653e\u5728\u4e0b\u4e00\u7bc7\u6587\u7ae0\u4e2d\u89e3\u91ca\uff09<\/li>\n<\/ol>\n
          vector<int> v = static_cast<vector<int>>(10); vector<int> v2 = static_cast<vector<int>&&>(v); cout << \"after move, v.size() = \" << v.size() << 'n'; cout << v.size() << endl; <\/code><\/pre>\n
            \n
          1. \u5b50\u7c7b\u6570\u7ec4\u6307\u9488\u5411\u4e0a\u8f6c\u6210\u7236\u7c7b\u7684\u6307\u9488<\/li>\n<\/ol>\n
            struct B {     int m = 0;     void hello() const {         cout << \"Hello world, this is B!n\";     } }; struct D : B {     void hello() const {         cout << \"Hello world, this is D!n\";     } };  D a[10]; B* dp = static_cast<B*>(a); dp->hello(); <\/code><\/pre>\n
              \n
            1. \u679a\u4e3e\u8f6c\u6362\u6210 int or float<\/li>\n<\/ol>\n
              enum E { ONE = 1, TWO, THREE }; E e = E::ONE; int one = static_cast<int>(e); cout << one << 'n'; <\/code><\/pre>\n
                \n
              1. int to enum, enum to another emum<\/li>\n<\/ol>\n
                enum class E { ONE = 1, TWO, THREE }; enum EU { ONE = 1, TWO, THREE };  E e = E::ONE; int one = static_cast<int>(e); E e2 = static_cast<E>(one); EU eu = static_cast<EU>(e2); <\/code><\/pre>\n
                  \n
                1. void* to any type<\/li>\n<\/ol>\n
                  int a = 100; void* voidp = &a; int *p = static_cast<int*>(voidp); <\/code><\/pre>\n
                  \u6ce8\u610f\uff1a<\/p>\n
                    \n
                  1. static_cast \u4e0d\u80fd\u8f6c\u6362\u6389 expression \u7684 const \u3001volatile \u548c__unaligned \u5c5e\u6027,<\/li>\n
                  2. \u7f16\u8bd1\u5668\u9690\u5f0f\u6267\u884c\u4efb\u4f55\u7c7b\u578b\u8f6c\u6362\u90fd\u53ef\u7531 static_cast \u663e\u793a\u5b8c\u6210<\/li>\n<\/ol>\n
                    dynamic_cast<\/h3>\n
                    dynamic_cast < new-type > ( expression )<\/code><\/p>\n
                    \u63a5\u4e0b\u6765\u662fdynamic_cast<\/code>:<\/p>\n
                    \u52a8\u6001\u6620\u5c04\u53ef\u4ee5\u6620\u5c04\u5230\u4e2d\u95f4\u5c42\u7ea7\uff0c\u5c06\u6d3e\u751f\u7c7b\u6620\u5c04\u5230\u4efb\u4f55\u4e00\u4e2a\u57fa\u7c7b\uff0c\u7136\u540e\u5728\u57fa\u7c7b\u4e4b\u95f4\u53ef\u4ee5\u76f8\u4e92\u6620\u5c04\u3002<\/p>\n
                    dynamic_cast \u5b9e\u73b0\u539f\u7406<\/strong>: \u5148\u6062\u590d\u6e90\u6307\u9488\u7684 RTTI \u4fe1\u606f\uff0c\u518d\u53d6\u76ee\u6807\u7684 RTTT \u4fe1\u606f\uff0c\u6bd4\u8f83\u4e24\u8005\u662f\u5426\u76f8\u540c\uff0c\u4e0d\u540c\u53d6\u76ee\u6807\u7c7b\u578b\u7684\u57fa\u7c7b; \u7531\u4e8e\u5b83\u9700\u8981\u68c0\u67e5\u4e00\u957f\u4e32\u57fa\u7c7b\u5217\u8868\uff0c\u6545\u52a8\u6001\u6620\u5c04\u7684\u5f00\u9500\u6bd4 typeid \u5927\u3002 <\/p>\n
                    dynamic_cast \u7684\u5b89\u5168\u6027<\/strong>: \u5982\u5b9e\u73b0\u539f\u7406\u6240\u8bf4\uff0cdynamic_cast<\/code>\u4f1a\u505a\u4e00\u7cfb\u5217\u7684\u7c7b\u578b\u68c0\u67e5\uff0c\u8f6c\u6362\u6210\u529f\u4f1a\u8fd4\u56de\u76ee\u6807\u7c7b\u578b\u6307\u9488\uff0c\u5931\u8d25\u5219\u4f1a\u8fd4\u56de NULL, \u76f8\u5bf9\u4e8estatic_cast<\/code>\u5b89\u5168\uff0c\u56e0\u4e3a static_cast<\/code>\u5373\u4f7f\u8f6c\u6362\u5931\u8d25\u4e5f\u4e0d\u4f1a\u8fd4\u56de NULL \u3002<\/p>\n
                    \u4f8b 2: \u8fd9\u79cd\u60c5\u51b5\u4e0b static_cast() \u4e5f\u662f\u5b89\u5168\u7684\u3002<\/strong><\/p>\n
                    class Base { public:     void func() { cout << \"Base func\" << endl; } };  class Derived : public Base { public:     void func() { cout << \"Derived func\" << endl; } };  int main(int argc, char const* argv[]) {     Derived *pd = new Derived;     pd->func();     Base* pb1 = dynamic_cast<Base*>(pd);     pb1->func();     Base* pb2 = static_cast<Base*>(pd);     pb2->func();     return 0; } <\/code><\/pre>\n
                    pd \u6307\u9488\u6307\u5411\u7684\u5185\u5b58\u662f\u5b50\u7c7b\u5bf9\u8c61\uff0c\u6211\u4eec\u77e5\u9053\uff0c\u7ee7\u627f\u5b50\u7c7b\u662f\u5305\u542b\u7236\u7c7b\u7684\uff0c\u76f8\u5f53\u4e8e\u5728\u7236\u7c7b\u7684\u57fa\u7840\u4e0a\u5728\u6dfb\u52a0\u5b50\u7c7b\u7684\u6210\u5458\uff08\u5982\u679c\u4f60\u8fd8\u4e0d\u6e05\u695a\u7684\u8bdd\uff0c\u5efa\u8bae\u4f60\u770b\u4e00\u4e0b\u6211\u4e4b\u524d\u7684\u6587\u7ae0: \u865a\u51fd\u6570\uff0c\u865a\u8868\u6df1\u5ea6\u5256\u6790\uff09\u3002 \u6240\u4ee5 pd \u6307\u9488\u8f6c\u6210\u7236\u7c7b\u6307\u9488\u4e5f\u662f\u6ca1\u95ee\u9898\u7684\uff0cstatic_cast<\/code>\u4e5f\u4e00\u6837\u5b89\u5168\u3002<\/p>\n
                    \u76f8\u53cd\uff0c\u5982\u679c\u6307\u9488\u6307\u5411\u7684\u5185\u5b58\u662f\u7236\u7c7b\u6210\u5458\uff0c\u8f6c\u6210\u5b50\u7c7b\u6307\u9488\uff0cdynamic_cast<\/code> \u5219\u4f1a\u5931\u8d25\uff0c\u8fd4\u56de NULL, \u4f46\u662fstatic_cast<\/code>\u4e0d\u4f1a\u5931\u8d25\uff0c\u5f3a\u5236\u8f6c\u8fc7\u53bb\u4e86\uff0c\u5982\u679c\u6b64\u65f6\u5b50\u7c7b\u6307\u9488\u8bbf\u95ee\u7236\u7c7b\u4e2d\u4e0d\u5b58\u5728\uff0c\u4f46\u662f\u5b50\u7c7b\u4e2d\u5b58\u5728\u7684\u6210\u5458\uff0c\u5219\u4f1a\u53d1\u751f\u610f\u60f3\u4e0d\u5230\u7684\u95ee\u9898\u3002<\/p>\n
                    \u770b\u4e0b\u9762\u8fd9\u4e2a\u4f8b\u5b50:<\/p>\n
                    class Base { public:     virtual void func() { cout << \"Base func\" << endl; } };  class Derived : public Base { public:     virtual void func() { cout << \"Derived func\" << endl; }     int m_value = 0; };  int main(int argc, char const* argv[]) {     Base *pb = new Base;     pb->func();     Derived* pd1 = dynamic_cast<Derived*>(pb);     if (pd1 != NULL) {         pd1->func();     } else {         cout << \"dynamic_cast failed\" << endl;     }     Derived* pd2 = static_cast<Derived*>(pb);     pd2->func();     cout << \"m_value: \" << pd2->m_value << endl;     return 0; } <\/code><\/pre>\n
                    \u8f93\u51fa:<\/p>\n
                    Base func dynamic_cast failed Base func  \/\/ \u7236\u7c7b\u4e2d\u4e5f\u6709\u8fd9\u4e2a\u865a\u51fd\u6570\uff0c\u6240\u4ee5 static_cast \u8f6c\u6362\u8c03\u7528\u6ca1\u51fa\u95ee\u9898\u3002 m_value: -33686019  \/\/ \u8fd9\u91cc\u51fa\u95ee\u9898\u4e86 <\/code><\/pre>\n
                    \u5bf9\u4e8e\u4e0a\u884c\u8f6c\u6362\uff0cstatic_cast<\/code> \u548c dynamic_cast<\/code> \u6548\u679c\u4e00\u6837\uff0c\u90fd\u5b89\u5168, \u5982\u679c\u53ea\u662f\u5355\u7eaf\u7684\u5411\u4e0a\u8f6c\u7684\u8bdd\uff0c\u6ca1\u5fc5\u8981\uff0c\u76f4\u63a5\u7528\u865a\u51fd\u6570\u5b9e\u73b0\u5c31\u597d\u4e86\u3002<\/p>\n
                    \u5bf9\u4e8e\u4e0b\u884c\u8f6c\u6362: \u4f60\u5fc5\u987b\u786e\u5b9a\u8981\u8f6c\u6362\u7684\u6570\u636e\u786e\u5b9e\u662f\u76ee\u6807\u7c7b\u578b\u7684\u6570\u636e\uff0c\u5373\u9700\u8981\u6ce8\u610f\u8981\u8f6c\u6362\u7684\u7236\u7c7b\u7c7b\u578b\u6307\u9488\u662f\u5426\u771f\u7684\u6307\u5411\u5b50\u7c7b\u5bf9\u8c61\uff0c\u5982\u679c\u662f\uff0cstatic_cast \u548c dynamic_cast \u90fd\u80fd\u6210\u529f\uff1b\u5982\u679c\u4e0d\u662f static_cast \u80fd\u8fd4\u56de\uff0c\u4f46\u662f\u4e0d\u5b89\u5168\uff0c\u53ef\u80fd\u4f1a\u51fa\u73b0\u8bbf\u95ee\u8d8a\u754c\u9519\u8bef\uff0c\u800c dynamic_cast \u5728\u8fd0\u884c\u65f6\u7c7b\u578b\u68c0\u67e5\u8fc7\u7a0b\u4e2d\uff0c\u5224\u5b9a\u8be5\u8fc7\u7a0b\u4e0d\u80fd\u8f6c\u6362\uff0c\u8fd4\u56de NULL \u3002<\/p>\n
                    const_cast<\/h3>\n
                    const_cast < new_type > ( expression )<\/code><\/p>\n
                    \u4e0a\u9762\u8bb2\u4e86static_cast<\/code>\u662f\u4e0d\u80fd\u53bb\u6389 const<\/code>\uff0c\u800c const_cast<\/code>\u662f\u4e13\u95e8\u7528\u6765\u53bb\u6389 const<\/code>\u3002<\/p>\n
                    \u800c\u6dfb\u52a0 const, static_cast<\/code> \u4e5f\u662f\u53ef\u4ee5\u6dfb\u52a0\u4e0a const\uff0c\u53ea\u662f\u4e0d\u80fd\u53bb\u6389 const<\/p>\n
                    \u770b\u4e0b\u9762\u4e00\u4e2a\u4f8b\u5b50:<\/p>\n
                    const int a = 26; const int* pa = &a; \/\/*pa = 3;  \/\/ \u7f16\u8bd1\u4e0d\u8fc7\uff0c\u6307\u9488\u5e38\u91cf\u4e0d\u80fd\u901a\u8fc7\u6307\u9488\u4fee\u6539\u503c  int* b = const_cast<int*>(pa);  \/\/ \u628a const \u8f6c\u6362\u6389 *b = 3;  cout << \"a: \" << a << endl;  \/\/ 26 cout << \"*b: \" << *b << endl;  \/\/ 3 <\/code><\/pre>\n
                    a \u4e3a const int<\/code> \u7c7b\u578b\uff0c\u4e0d\u53ef\u4fee\u6539\uff0cpa \u4e3a const int*<\/code> \u7c7b\u578b\uff0c\u4e0d\u80fd\u901a\u8fc7 pa \u6307\u9488\u4fee\u6539 a \u7684\u503c<\/p>\n
                    b \u901a\u8fc7 const_cast<\/code> \u8f6c\u6362\u6389\u4e86 const\uff0c\u6210\u529f\u4fee\u6539\u4e86 a \u7684\u503c\u3002<\/p>\n
                    \"C++<\/p>\n
                    \u6709\u4e00\u4e2a\u95ee\u9898\uff0c\u4e3a\u4ec0\u4e48 a \u8f93\u51fa\u662f 26 \u5462\uff1f<\/p>\n
                    \u5982\u679c\u5b58\u5728const int x = 26;<\/code> \u8fd9\u79cd\u60c5\u51b5\uff0c\u90a3\u4e48\u7f16\u8bd1\u5668\u4f1a\u8ba4\u4e3a x \u662f\u4e00\u4e2a\u7f16\u8bd1\u671f\u53ef\u8ba1\u7b97\u51fa\u7ed3\u679c\u7684\u5e38\u91cf\uff0c\u90a3\u4e48 x \u5c31\u4f1a\u50cf\u5b8f\u5b9a\u4e49\u4e00\u6837\uff0c\u7528\u5230 x \u7684\u5730\u65b9\u4f1a\u88ab\u7f16\u8bd1\u5668\u66ff\u6362\u6210 26 \u3002<\/p>\n
                    \u4e0a\u8ff0\u8fd9\u4e2a\u4f8b\u5b50\u4e0d\u5efa\u8bae\u4f7f\u7528\uff0c\u56e0\u4e3a a \u58f0\u660e\u4e3a const int<\/code> \u7c7b\u578b\uff0c\u5b9e\u9645\u4e0a\u662f\u5e76\u4e0d\u5e0c\u671b\u88ab\u4fee\u6539\u7684\uff0c\u8fd9\u6837\u5f3a\u884c\u4fee\u6539\u53ef\u80fd\u4f1a\u5bfc\u81f4\u9879\u76ee\u91cc\u4e0d\u53ef\u9884\u671f\u7684\u9519\u8bef\u3002<\/p>\n
                    const_cast \u7684\u4f7f\u7528\u573a\u666f<\/strong><\/p>\n
                      \n
                    1. \u5982\u679c\u6709\u4e00\u4e2a\u51fd\u6570\uff0c\u5b83\u7684\u5f62\u53c2\u662f non-const \u7c7b\u578b\u53d8\u91cf\uff0c\u800c\u4e14\u51fd\u6570\u4e0d\u4f1a\u5bf9\u5b9e\u53c2\u7684\u503c\u8fdb\u884c\u6539\u52a8\uff0c\u8fd9\u65f6\u6211\u4eec\u53ef\u4ee5\u4f7f\u7528\u7c7b\u578b\u4e3a const \u7684\u53d8\u91cf\u6765\u8c03\u7528\u51fd\u6570\u3002<\/li>\n<\/ol>\n
                      void func(int* a) { }  int main() {     const int a = 26;     const int* pa = &a;     func(const_cast<int*>(pa)); } <\/code><\/pre>\n
                      \u8fd9\u79cd\u60c5\u51b5\u5176\u5b9e\u6211\u89c9\u5f97\u6ca1\u5fc5\u8981\uff0c\u5b9e\u9645\u4e0a\u6211\u4e0d\u60f3\u6539\u7684\u8bdd\uff0c\u6211\u5f62\u53c2\u52a0 const\uff0c\u628a\u524d\u63d0\u63a8\u7ffb\u4e0d\u5c31\u884c\u4e86\uff0c\u8fd8\u5b89\u5168\u3002<\/p>\n
                        \n
                      1. \u5b9a\u4e49\u4e86\u4e00\u4e2a non-const \u7684\u53d8\u91cf\uff0c\u5374\u4f7f\u7528\u4e86\u4e00\u4e2a\u6307\u5411 const \u503c\u7684\u6307\u9488\u6765\u6307\u5411\u5b83\uff08\u8fd9\u4e0d\u662f\u6ca1\u4e8b\u627e\u4e8b\u561b\uff09\uff0c\u5728\u7a0b\u5e8f\u7684\u67d0\u5904\u6211\u4eec\u60f3\u6539\u53d8\u8fd9\u4e2a\u53d8\u91cf\u7684\u503c\u4e86\uff0c\u4f46\u624b\u5934\u53ea\u6301\u6709\u6307\u9488\uff0c\u8fd9\u65f6const_cast<\/code>\u5c31\u53ef\u4ee5\u7528\u5230\u4e86<\/li>\n<\/ol>\n
                        int a = 26; const int* pa = &a; \/\/ *pa = 1; \u7f16\u8bd1\u4e0d\u8fc7 int* pa2 = const_cast<int*>(pa); *pa2 = 1; <\/code><\/pre>\n
                        reinterpret_cast<\/h3>\n
                        reinterpret_cast < new_type > ( expression )<\/code><\/p>\n
                        reinterpret_ cast \u901a\u5e38\u4e3a\u64cd\u4f5c\u6570\u7684\u4f4d\u6a21\u5f0f\u63d0\u4f9b\u8f83\u4f4e\u5c42\u7684\u91cd\u65b0\u89e3\u91ca\u3002<\/p>\n
                        \u770b\u8fd9\u4e2a\u4f8b\u5b50:<\/p>\n
                        int n = 9; double d = static_cast<double>(n);  cout << n << \" \" << d; \/\/ \u8f93\u51fa 9 9  int n2 = 9; double d2 = reinterpret_cast<double&>(n2); cout << n2 << \" \" << d2; \/\/ \u8f93\u51fa 9 -9.25596e+61 <\/code><\/pre>\n
                        \u4e0a\u9762\u7684\u4f8b\u5b50\u4e2d\uff0c\u6211\u4eec\u5c06\u4e00\u4e2a\u53d8\u5740\u4ece int \u8f6c\u6362\u5230 double \u3002\u8fd9\u4e9b\u7c7b\u578b\u7684\u4e8c\u8fdb\u5236\u8868\u8fbe\u5f0f\u662f\u4e0d\u540c\u7684\u3002\u8981\u5c06\u6574\u6570 9 \u8f6c\u6362\u5230\u53cc\u7cbe\u5ea6\u6574\u6570 9, static_cast \u9700\u8981\u6b63\u786e\u5730\u4e3a\u53cc\u7cbe\u5ea6\u6574\u6570 d \u8865\u8db3\u6bd4\u7279\u4f4d\u3002\u5176\u7ed3\u679c\u4e3a 9.0 \u3002<\/p>\n
                        \u800c reinterpret_cast \u7684\u884c\u4e3a\u5374\u4e0d\u540c\uff0c\u4ec5\u4ec5\u662f\u628a\u5185\u5b58\u62f7\u8d1d\u5230\u76ee\u6807\u7a7a\u95f4\uff0c\u89e3\u91ca\u51fa\u6765\u662f\u4e00\u4e2a\u5927\u6570\u3002<\/p>\n
                        \"C++ \"C++ \"C++<\/p>\n
                        reinterpret_cast \u8fd9\u4e2a\u64cd\u4f5c\u7b26\u88ab\u7528\u4e8e\u7684\u7c7b\u578b\u8f6c\u6362\u7684\u8f6c\u6362\u7ed3\u679c\u51e0\u4e4e\u90fd\u662f\u672a\u77e5\u7684\u3002<\/p>\n
                        \u4f7f\u7528 reinterpret_cast \u7684\u4ee3\u7801\u5f88\u96be\u79fb\u690d\u3002\u8f6c\u6362\u51fd\u6570\u6307\u9488\u7684\u4ee3\u7801\u662f\u4e0d\u53ef\u79fb\u690d\u7684\uff0c\uff08 C++\u4e0d\u4fdd\u8bc1\u6240\u6709\u7684\u51fd\u6570\u6307\u9488\u90fd\u88ab\u7528\u4e00\u6837\u7684\u65b9\u6cd5\u8868\u793a\uff09\uff0c\u5728\u4e00\u4e9b\u60c5\u51b5\u4e0b\u8fd9\u6837\u7684\u8f6c\u6362\u4f1a\u4ea7\u751f\u4e0d\u6b63\u786e\u7684\u7ed3\u679c\u3002 \u6240\u4ee5\u5e94\u8be5\u907f\u514d\u8f6c\u6362\u51fd\u6570\u6307\u9488\u7c7b\u578b\uff0c\u6309\u7167 C++\u65b0\u601d\u7ef4\u7684\u8bdd\u6765\u8bf4\uff0creinterpret_cast \u662f\u4e3a\u4e86\u6620\u5c04\u5230\u4e00\u4e2a\u5b8c\u5168\u4e0d\u540c\u7c7b\u578b\u7684\u610f\u601d\uff0c\u8fd9\u4e2a\u5173\u952e\u8bcd\u5728\u6211\u4eec\u9700\u8981\u628a\u7c7b\u578b\u6620\u5c04\u56de\u539f\u6709\u7c7b\u578b\u65f6\u7528\u5230\u5b83\u3002 \u6211\u4eec\u6620\u5c04\u5230\u7684\u7c7b\u578b\u4ec5\u4ec5\u662f\u4e3a\u4e86\u6545\u5f04\u7384\u865a\u548c\u5176\u4ed6\u76ee\u7684\uff0c\u8fd9\u662f\u6240\u6709\u6620\u5c04\u4e2d\u6700\u5371\u9669\u7684\u3002reinterpret_cast \u5c31\u662f\u4e00\u628a\u9510\u5229\u65e0\u6bd4\u7684\u53cc\u5203\u5251\uff0c\u9664\u975e\u4f60\u5904\u4e8e\u80cc\u6c34\u4e00\u6218\u548c\u706b\u70e7\u7709\u6bdb\u7684\u5371\u6025\u65f6\u523b\uff0c\u5426\u5219\u7edd\u4e0d\u80fd\u4f7f\u7528\u3002<\/p>\n
                        \u5176\u5b9e reinterpret_cast<\/code> \u7528\u6cd5\u7ec6\u8282\u8fd8\u6709\u4e0d\u5c11\uff0c\u4ec0\u4e48\u65f6\u5019\u9700\u8981\u7528\u5230\uff0c\u518d\u53bb\u5b98\u65b9\u4e86\u89e3\u4e00\u4e0b\u5c31\u597d\u4e86\uff0c\u73b0\u5728\u7ea0\u7684\u592a\u7ec6\u610f\u4e49\u4e0d\u5927\u3002 \"C++<\/p>\n<\/p><\/div>\n
                         \u5927\u4f6c\u6709\u8a71\u8aaa<\/b> (2<\/span>)        <\/div>\n
                         <\/div>\n<\/p><\/div>\n<\/p><\/div>\n
                          \n
                        • \n
                          \n
                          \n
                           \u8cc7\u6df1\u5927\u4f6c : chesterzzy <\/span>  <\/div>\n
                           <\/i>            <\/span> <\/div>\n<\/p><\/div>\n
                                                                                       \u8bb2\u5f97\u633a\u597d\u7684\uff0c\u5df2\u5173\u6ce8\u516c\u4f17\u53f7                                                            <\/div>\n<\/p><\/div>\n<\/li>\n
                        • \n
                          \n
                          \n
                           \u4e3b<\/span> \u8cc7\u6df1\u5927\u4f6c : yiouejv <\/span>  <\/div>\n
                           <\/i>            <\/span> <\/div>\n<\/p><\/div>\n
                                                                                       @chesterzzy \u563f\u563f\uff0c\u4e00\u8d77\u5b66\u4e60                                                            <\/div>\n<\/p><\/div>\n<\/li>\n
                        • \n","protected":false},"excerpt":{"rendered":"
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