ARTICLE AD BOX
I believe that constructors cannot be declared virtual for the following reason:
Calling a virtual function requires the vtable pointer (vptr) to have already been correctly initialized, so that it points to the appropriate virtual function table. Only then can the correct function be resolved through virtual dispatch. However, the correct initialization of the vptr itself happens during object construction. If constructors were allowed to be virtual, this would lead to a problem: calling a virtual constructor would require the vptr to have already been correctly initialized, but initializing the vptr would in turn require the constructor to be called, resulting in a circular dependency.
However, GPT argues that the statement “the correct initialization of the vptr happens in the constructor” is incorrect. According to GPT, the fundamental reason constructors cannot be virtual is not an implementation limitation, but a semantic one: the semantics of virtual dispatch conflict with the semantics of object construction. Therefore, constructors are disallowed from being virtual because virtual dispatch during construction is semantically ill-defined, not because it is technically impossible to implement.
