(C++) How can I get the size of an object from a pointer to a base class?
class Class{
public:
int Something;
};
class DerClass : public Class{
public:
int Array[256];
};
main()
{
Class*C = new DerClass;
sizeof(*C); // = 4
sizeof(DerClass); // = 1028
}
// How can I get 1028 from pointer C?
(C++) How can I get the size of an object from a pointer to a base class?c++ compiler
As far as I know, in c++ it is impossible to get the size of an object just from the base class and sizeof function. One way to get around this is to use dynamic_cast as follows.
struct A {
int a;
virtual ~A() {}
};
struct B : public A {
int b[128];
virtual ~B() {}
};
struct C : public A {
int c[256];
virtual ~C() {}
};
size_t sizeofA(A* a) {
if (dynamic_cast<C*>(a))
return sizeof(C);
else if (dynamic_cast<B*>(a))
return sizeof(B);
else
return sizeof(A);
}
(C++) How can I get the size of an object from a pointer to a base class?c++ cli
sizeof() hard codes size of objects into the program at compile time. Allocated (ie: 'new') memory block sizes are unknown until run time, making sizeof() hopeless to help.
So, don't think it can be done via pointer.
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