When can typeid return different type_info instances for same type?

Question

Andrei Alexandrescu writes in Modern C++ Design:

The objects returned by typeid have static storage, so you don\'t have to worry abou

Answer 1

Are there times when &typeid(T) != &typeid(T)?

I'm mainly interested in compilers for Windows, but any information for Linux and other platforms is also appreciated.

Yes. Under windows DLL can't have unresolved symbols, thus. If you have:

foo.h

struct foo { virtual ~foo() {} };

dll.cpp

#include "foo.h"
...
foo f;
cout << &typeid(&f) << endl

main.cpp

#include "foo.h"
...
foo f;
cout << &typeid(&f) << endl

Would give you different pointers. Because before dll was loaded typeid(foo) should exist in both dll and primary exe

More then that, under Linux, if main executable was not compiled with -rdynamic (or --export-dynamic) then typeid would be resolved to different symbols in executable and in shared object (which usually does not happen under ELF platforms) because of some optimizations done when linking executable -- removal of unnecessary symbols.