typeinfo

来源： https://stackoverflow.com/questions/26301024/c-methods-of-store-type-info-objects-doesnt-work

问题 I have a set of polymorphic C++ classes and they are all instantiated by the same module (Windows DLL). Now having two pointers to such classes and having called typeid : SomeCommonBase* first = ...; //valid pointer SomeCommonBase* second = ...; //valid pointer const type_info& firstInfo = typeid( first ); const type_info& secondInfo = typeid( second ); can I compare retrieved type_info addresses if( &firstInfo == &secondInfo ) { //objects are of the same class } else { //objects are of

问题 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

问题 So I have experimented on calling ITypeInfo on a VBA Class instance and whilst it looks promising I wanted to see if I could get a reference to its containing project, an analogue to a type library. I thought ITypeInfo.GetContainingTypeLib might be useful but it throws an exception indicating VBA won't co-operate. Anyone got any ideas about how VBA maybe doing things differently from the standard COM specification? The C# Class library code is here. Register for COM interop and set COMVisible

问题 After trying to debug an unsuccessful dynamic downcasting, I eventually found that the reason probably is: type_info::hash_code for the type it is casted to is not the same depending where in the code it is called. type_info::name stays exactly the same though. Unfortunately I'm unable to reproduce the behavior in a minimal example since it appears in a quite entangled context. Therefore I'm essentially looking for clues of what can be the cause of such behavior, and consequently what

问题 I have need to print indented template names for debugging purposes. For example, instead of single-line, I would like to indent name like this: boost::phoenix::actor< boost::phoenix::composite< boost::phoenix::less_eval, boost::fusion::vector< boost::phoenix::argument<0>, boost::phoenix::argument<1>, I started writing my own but is getting to be complicated. Is there an existing solution? if there is not one, can you help me to finish up my implementation? I will post it if so. Thanks this

问题 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"

问题 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 回答1: make sure the base class has at least one virtual method,

问题 Microsoft has a decades old bug when using its leak check gear in debug builds. The leak is reported from the allocation made by the runtime library when using C++ type information, like typeinfo.name() . Also see Memory leaks reported by debug CRT inside typeinfo.name() on Microsoft Connect. We've been getting error reports and user list discussions because of the leaks for about the same amount of time. The Microsoft bug could also mask real leaks from user programs. The latter point is

问题 So, I've got an application that uses boost::asio. Due to complexity of the project, I cannot share it's source code, sadly :( The application uses boost's asio lib to create some webservices. When attempting to use it, however, there's a sigsegv in std::type_info::operator==, which, as I'm aware, should rather work. (gdb) backtrace #0 0x0000000000457b79 in std::type_info::operator== ( this=0x7ffff6dadf61 <typeinfo for boost::asio::detail::typeid_wrapper<boost::asio::deadline_timer_service