What is a pseudo-virtual function in C++?

Question

What is a pseudo-virtual function in C++?

Answer 1

AFAIK it's not a term that appears anywhere with an official definition.

Perhaps someone is talking about simulated dynamic binding?

Edit: a swift web search suggests that someone might have implemented their own dynamic polymorphism, so they perhaps have their own vtables. "Pseudo-virtual" functions would then be functions accessed through their mechanism, rather than actually being virtual functions as their C++ compiler understands them.

One reason to do this would be to implement multi-dispatch.

Do you have any context you can point us at?

Answer 2

A virtual function with a declaration.

class Foo
{
    int* bar;

    Foo() : bar(0) { bar = new int; }
    virtual ~Foo() { delete bar; }
}

This has a pseudo-virtual destructor, since it does something in the declaration. Here is a pure virtual declaration:

class Foo
{
    Foo() { }
    virtual ~Foo()=0;
}

At least, this is how I learned it.

Answer 3

I have heard the term to used to refer to multimethods (in C++ these are usually implemented using an array of function pointers where the selector offset determined by the code at runtime):

(*multiMethod[ index ])()

The multiMethod array is just an array of function pointers.

Answer 4

I've never heard this term. I'd guess they're either talking about the Non-Virtual Interface idiom (NVI) or they're talking about building a dispatch table of function pointers which is how one might implement polymorphism/virtual functions in C (and in fact is how C++ compilers do it behind the scenes).