Question

Say the object is

class A {
public :  void Silly(){
    this = 0x12341234;
}

I know I will get compiler error ‘ “this” is not a lvalue.’ But then it is not a temporary either. So what is the hypothetical declaration of “this” ?

Compiler : GCC 4.2 compiler on mac.

Answer 1

For some class X, this has the type X* this;, but you’re not allowed to assign to it, so even though it doesn’t actually have the type X *const this, it acts almost like it was as far as preventing assignment goes. Officially, it’s a prvalue, which is the same category as something like an integer literal, so trying to assign to it is roughly equivalent to trying to assign a different value to 'a' or 10.

Note that in early C++, this was an lvalue — assigning to this was allowed — you did that to handle the memory allocation for an object, vaguely similar to overloading new and delete for the class (which wasn’t supported yet at that time).