I am wondering what the difference is between typeid
and typeof
in C++. Here's what I know:
typeid
is mentioned in the documentation for type_info which is defined in the C++ header file typeinfo.typeof
is defined in the GCC extension for C and in the C++ Boost library.
Also, here is test code test that I've created where I've discovered that typeid
does not return what I expected. Why?
main.cpp
#include <iostream>
#include <typeinfo> //for 'typeid' to work
class Person {
public:
// ... Person members ...
virtual ~Person() {}
};
class Employee : public Person {
// ... Employee members ...
};
int main () {
Person person;
Employee employee;
Person *ptr = &employee;
int t = 3;
std::cout << typeid(t).name() << std::endl;
std::cout << typeid(person).name() << std::endl; // Person (statically known at compile-time)
std::cout << typeid(employee).name() << std::endl; // Employee (statically known at compile-time)
std::cout << typeid(ptr).name() << std::endl; // Person * (statically known at compile-time)
std::cout << typeid(*ptr).name() << std::endl; // Employee (looked up dynamically at run-time
// because it is the dereference of a pointer
// to a polymorphic class)
}
output:
bash-3.2$ g++ -Wall main.cpp -o main
bash-3.2$ ./main
i
6Person
8Employee
P6Person
8Employee
name()
is implementation-defined. It doesn't have to be a valid C++ identifier name, just something that uniquely identifies the type. Looks like your implementation uses the compiler's general name-mangling scheme. – Rob Kennedy