c++ - dynamic_cast to the same type does not check type of object -

i trying determine whether object pointed t* pointer t object, or other, unrelated type. tried dynamic_cast, less useless, returns pointer instead of null when obvious not point valid t object:

object* garbage = reinterpret_cast<object*>(0x12345678); if( dynamic_cast<object*>(garbage) == null ){     cout << "expected behaviour (by me)" << endl; }else{     cout << "you've got kidding me" << endl; } 

is there workaround this, or other solution? i've tried casting void* , char* before dynamic_cast no avail, typeid not enough either since want accept subclasses well.

some context: i'm writing custom array class implementing shallow conversion between different kinds of arrays, array<object*> , array<string*>, , guarantee minimal type safety doing dynamic type check @ every element access, example:

#define debug array<string*> v(10); array<object*> o = v; o[0] = new integer(1);      //  technically illegal no idea how check //array<string*> w = o;     //  fails exception string* str = v[0];         //  should fail horribly cout << str << endl; 

casting object*, doing type check on object* works in lot of cases, fails in case of array<object*>, though not sure whether possible insert non-object array<object*> without use of reinterpret_cast.

base on example, sounds you've got shallow copy arrays trick containing different types supposed contain. think "normal" solution problem make difficult users (i.e. don't provide conversions between array<t> , array<u>). but, if you're set in ideas think work:

template<typename subclass> class array { public:     // ...     subclass *operator [] (size_t index) {         assert( index < size_ );         assert( dynamic_cast<subclass*>(static_cast<object*>(internal_[index])) != null );         // ...     }     // ... private:     size_t size_;     subclass **internal_; }; 

you can template meta-magic , static assert make sure subclass subclass of object (exactly how different topic). once out of way, casting down object* , subclass dynamic_cast should accomplish goal.