typeinfo

This question already has answers here : Closed 7 years ago . Possible Duplicate: g++ undefined reference to typeinfo Undefined symbols “vtable for …” and “typeinfo for…”? I can't use my class. class Accel { public: virtual void initialize(void); virtual void measure(void); virtual void calibrate(void); virtual const int getFlightData(byte); }; class Accel_ad : public Accel { public: Accel_ad() : Accel(){} void initialize(void) {/*code code code...*/} void measure(void) {/*measure code*/} const int getFlightData(byte axis){/*getting data*/} void calibrate(void) { int findZero[FINDZERO]; int

The std::type_info class is non-copyable. This makes it hard to store it in an object for later use. What should I do? Silicomancer There is a much better solution in C++11. A new copyable wrapper called std::type_index. You need to include header "typeindex" to use it. You can store a pointer to a constant std::type_info object. matejk From MSDN and IBM online documentation : The type_info class describes type information generated within the program by the compiler. Objects of this class effectively store a pointer to a name for the type. The type_info class also stores an encoded value

I know that compilers have much freedom in implementing std::type_info functions' behavior. I'm thinking about using it to compare object types, so I'd like to be sure that: std::type_info::name must return two different strings for two different types. std::type_info::before must say that Type1 is before Type2 exclusive-or Type2 is before Type1 . // like this: typeid(T1).before( typeid(T2) ) != typeid(T2).before( typeid(T1) ) Two different specialization of the same template class are considered different types. Two different typedef -initions of the same type are the same type. And finally:

According to cplusplus.com, the std::type_info::before() function... Returns true if the type precedes the type of rhs in the collation order. The collation order is just an internal order kept by a particular implementation and is not necessarily related to inheritance relations or declaring order. So what is it useful for? Consider you want to put your type_info objects as keys into a map<type_info*, value> . The type_info doesn't have an operator < defined, so you must provide your own comparator. The only thing that is guaranteed to work from the type_info interface is the before()

I used typeid to get the type names of the std::vector::size_type and a zero sized class A with the following code ( cppreference ): #include<iostream> #include <vector> #include <typeinfo> using namespace std; class A {}; int main() { vector<int> v(10); vector<int>::size_type s = v.size(); A a; cout << typeid(s).name() << endl; cout << typeid(a).name() << endl; }; And I got this as output: m 1A I guess that "1" before "A" is a result of the Empty Base Class Optimization, but what does "m" stand for and is this normal? I am using the following gcc version: g++ (Ubuntu 4.4.3-4ubuntu5.1) 4.4.3 G

Lets say we have a class hierarchy. At the bottom we have Base and at the top Derived. How to determine object class even if it is converted to base class pointer. Base* b = new Derived(): typeid(b).name(); // i want this to tell me that this is actually derived not base object is there any way other than manual implementation of string field or such and virtual get function? PS: I talking about compiler-independent solution make sure the base class has at least one virtual method, include <typeinfo> and use your current code just with an additional dereferencing, typeid(*b).name() . in