C++ typeid关键字

#include <assert.h> #include <iostream> #include <string> #include <typeinfo> #include <vector> #include <cstdio> using namespace std; int func(int a) { return 0; } typedef int(*fun_ptr)(int); class Base { public: Base() {} }; int test_typeid1() { char char_ = 'a'; unsigned char uchar_ = 'b'; short short_ = -16; unsigned short ushort_ = 16; int int_ = -1024; unsigned int uint_ = 1024; float float_ = 1.2f; double double_ = 2.34; long long_ = -12222; long long llong_ = 12222; int array[10] = { 0 }; int* array_ptr = array; string string_("xiongwei"); vector<int> int_vector; fun_ptr f = func; Base base_; Base* pBase = new Base; Base& rBase = base_; cout << "char_ type: " << typeid(char_).name() << std::endl; assert(typeid(char).name() == typeid(char_).name()); std::cout << "uchar type: " << typeid(uchar_).name() << std::endl; // uchar type: unsigned char assert(typeid(unsigned char).name() == typeid(uchar_).name()); std::cout << "short_ type: " << typeid(short_).name() << std::endl; // short_ type: short assert(typeid(short).name() == typeid(short_).name()); std::cout << "ushort_ type: " << typeid(ushort_).name() << std::endl; // ushort_ type: unsigned short assert(typeid(unsigned short).name() == typeid(ushort_).name()); std::cout << "int_ type: " << typeid(int_).name() << std::endl; // int_ type: int assert(typeid(int).name() == typeid(int_).name()); std::cout << "uint_ type: " << typeid(uint_).name() << std::endl; // uint_ type: unsigned int assert(typeid(unsigned int).name() == typeid(uint_).name()); std::cout << "float_ type: " << typeid(float_).name() << std::endl; // float_ type: float assert(typeid(float).name() == typeid(float_).name()); std::cout << "double_ type: " << typeid(double_).name() << std::endl; // double_ type: double assert(typeid(double).name() == typeid(double_).name()); std::cout << "long_ type: " << typeid(long_).name() << std::endl; // long_ type: long assert(typeid(long).name() == typeid(long_).name()); std::cout << "llong_ type: " << typeid(llong_).name() << std::endl; // llong_ type: __int64 assert(typeid(long long).name() == typeid(llong_).name()); std::cout << "array[] type: " << typeid(array).name() << std::endl; // array[] type: int [10] assert(typeid(int[10]).name() == typeid(array).name()); std::cout << "array_header type: " << typeid(array_ptr).name() << std::endl; // array_header type: int * __ptr64 assert(typeid(int*).name() == typeid(array_ptr).name()); std::cout << "string_ type: " << typeid(string_).name() << std::endl; // string_ type: class std::basic_string<char,struct std::char_traits<char>, class std::allocator<char>> assert(typeid(std::string).name() == typeid(string_).name()); std::cout << "int_vector type: " << typeid(int_vector).name() << std::endl; // int_vector type: class std::vector<int,class std::allocator<int>> assert(typeid(std::vector<int>).name() == typeid(int_vector).name()); std::cout << "f type: " << typeid(f).name() << std::endl; // f type : int(__cdecl*)(int) assert(typeid(int(*)(int)).name() == typeid(f).name()); std::cout << "Base_ type: " << typeid(base_).name() << std::endl; // Base_ type: class Base assert(typeid(class Base).name() == typeid(base_).name()); std::cout << "pBase_ type: " << typeid(pBase).name() << std::endl; // pBase_ type: class Base * __ptr64 assert(typeid(class Base*).name() == typeid(pBase).name()); std::cout << "rBase_ type: " << typeid(rBase).name() << std::endl; // Base__ type: class Base assert(typeid(class Base&).name() == typeid(rBase).name()); return 0; } void test_typeid2() { struct Base { }; // non-polymorphic struct Derived : Base { }; struct Base2 { virtual void foo() {} }; // polymorphic struct Derived2 : Base2 { }; int myint = 50; std::string mystr = "string"; double *mydoubleptr = NULL; std::cout << "myint has type: " << typeid(myint).name() << '\n' // myint has type: int << "mystr has type: " << typeid(mystr).name() << '\n' // mystr has type: class std::basic_string<char, struct std::char_traits<char>, class std::allocator<char>> << "mydoubleptr has type: " << typeid(mydoubleptr).name() << '\n'; // mydoubleptr has type: double * __ptr64 // std::cout << myint is a glvalue expression of polymorphic type; it is evaluated const std::type_info& r1 = typeid(std::cout); // 50 std::cout << "#std::cout<<myint has type : " << r1.name() << '\n'; // std::cout<<myint has type: class std::basic_ostream<char, struct std::char_traits<char>> const std::type_info& r2 = typeid(std::printf("%d\n", myint)); std::cout << "printf(\"%d\\n\",myint) has type : " << r2.name() << '\n'; // printf(\"%d\\n\",myint) has type : int Derived d1; Base& b1 = d1; std::cout << "reference to non-polymorphic base: " << typeid(b1).name() << '\n'; // reference to non-polymorphic base: struct 'int __cdecl test_typeid2(void)'::'2'::Base Derived2 d2; Base2& b2 = d2; std::cout << "reference to polymorphic base: " << typeid(b2).name() << '\n'; // reference to polymorphic base: struct 'int __cdecl test_typeid2(void)'::'3'::Derived2 try { // dereferencing a null pointer: okay for a non-polymoprhic expression std::cout << "mydoubleptr points to " << typeid(*mydoubleptr).name() << '\n'; // mydoubleptr points to double // dereferencing a null pointer: not okay for a polymorphic lvalue Derived2* bad_ptr = NULL; std::cout << "bad_ptr points to..."; // bad_ptr points to... std::cout << typeid(*bad_ptr).name() << '\n'; } catch (const std::bad_typeid& e) { std::cout << " caught " << e.what() << '\n'; // caught Attempted a typeid of NULL pointer! } } template < typename T > T max(T arg1, T arg2) { std::cout << typeid(T).name() << "s compared." << std::endl; return (arg1 > arg2 ? arg1 : arg2); } int test_typeid3() { class Base { public: virtual void vvfunc() {} }; class Derived : public Base {}; Derived* pd = new Derived; Base* pb = pd; std::cout << typeid(pb).name() << std::endl; //prints "class Base *" // class 'int __cdecl test_typeid3(void)'::'2'::Base * __ptr64 std::cout << typeid(*pb).name() << std::endl; //prints "class Derived" // class 'int __cdecl test_typeid3(void)'::'2'::Derived std::cout << typeid(pd).name() << std::endl; //prints "class Derived *" // class 'int __cdecl test_typeid3(void)'::'2'::Derived * __ptr64 std::cout << typeid(*pd).name() << std::endl; //prints "class Derived" // class 'int __cdecl test_typeid3(void)'::'2'::Derived delete pd; float a = 1.2, b = 3.4; max(a, b); // floats compared max<int>(1,2); return 0; } int main() { test_typeid1(); cout << "---------------------------------------" << endl; test_typeid2(); test_typeid3(); system("pause"); return 0; }

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