Re: What does Ctor::Ctor prototype mean?
On 29 Jul., 17:09, persres <pers...@googlemail.com> wrote:
Hi,
For a class ABC. Can we declare the Ctor as ABC::ABC()?
This syntax does not have a meaning, if the c'tor is defined
within the class ABC. It is necessary to use this qualification,
if the member were defined outside the class as in the following
example:
struct A {
A(); // OK, just declared
};
A::A() {} // Definition
This makes sense, because the definition is in the context
of the surrounding namespace. Within this context, a class
member needs to be accessed via qualification with the
class name (or via member access).
In particular for a class template, what is the semantics?
Please look at the code below. It doesn't compile on VC2008.
The code is ill-formed and should be rejected.
class Base
{
public:
Base::Base() {}
virtual ~Base() {}} ;
template <class T>
class ABC : public Base
{
public:
ABC::ABC() {} // Line 16 error
~ABC() {}
};
int main()
{
ABC<int> sp;
}
The errors are -
main.cpp(16) : error C3254: 'ABC<T>' : class contains explicit
override '{ctor}' but does not derive from an interface that contains
the function declaration
main.cpp(18) : see reference to class template instantiation 'ABC<T>'
being compiled
main.cpp(16) : error C3244: 'ABC<T>::ABC(void)' : this method was
introduced by '<Unknown>' not by 'Base'
What do these errors mean? Is ABC::ABC legal for a plain class? Is it
a specialization for a template class?
The compiler is just complaining that your code is ill-
formed. The error message could be improved, but you
cannot imply any reasonable interpretation from that.
HTH & Greetings from Bremen,
Daniel Kr?gler
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