Is C++ value of this guaranteed? -

consider have class foo (that not have & operator overloaded) address obtained & operator of class guaranteed have same value this pointer?

in code below equalpointer guaranteed return true? there cases return false (e.g. when considering multiple inheritance)?

class foo {   bool equalpointer(const foo * f} { return f==this; } } foo f; f.equalpointer(&f); 

the issue 1 of memory layout. standard doesn't guarantee memory layout, in particular doesn't guarantee no offset exists between derived , base class...

for example:

class foo: public boost::noncopyable { public:   virtual ~foo(); }; 

because boost::noncopyable doesn't have virtual method, in gcc (void*)(foo*)&f , (void*)(boost::noncopyable*)&f have different values.

but not matter in practice, because compiler perform necessary adjustments. is, if compare foo* should fine , dandy...

... apart multiple inheritance might break this, if there several foo subobjects in hierarchy.

on other hand, should in 1 of 2 cases:

• either there no hierarchy (no virtual) , can compare address of objects is
• or there hierarchy (and virtual method) , use dynamic_cast<void*>(&f) address of complete object.

therefore, template method, give:

template <typename t, typename u> bool have_same_dynamic_location(t const& t, u const& u) {   return dynamic_cast<void*>(&t) == dynamic_cast<void*>(&u); } 

(which valid if both t , u have virtual methods)