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Re: [vox-tech] C++ virtual function question
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Re: [vox-tech] C++ virtual function question

Hai Yi wrote:
> I am not sure this is a right place to ask a C++ question, but I
> noticed some people posted C questions before.
> This is a code snippet from the book "C++ FAQ",
> class Base{
> public:
> virtual ~Base() throw();
> };
> class Derived: public Base{
> };
> int main(){}

Give the body of main some meat... e.g.:

int main()
  Derived *dptr = new Derived;
  Base *bptr = dptr;
  delete bptr;

> according to the author, it should have a link problem, because,
> direct quote :"The reason is that the only virtual function in class
> Derived is inline, so the compiler puts a static copy of
> Derived::~Derived() into the current source file. Since this static
> copy of Derived::~Derived() invokes Base::~Base() the linker will need
> a definition of Base::~Base()"

I don't think the described implementation is the only way the compiler
could handle this, since inlining is optional on the part of the compiler.

> However, when I run this program, it worked fine. Is it my
> misunderstanding or my system gave this code a pass? (the author say
> it will fail on many systems...)

The compiler never generated any code to instantiate the troublesome 
objects, so the problem never appeared.

> Thanks for any ideas!

Be sparing in your use of inline functions... they should be VERY simple
or you can get serious object code bloat.

Jeff Newmiller                        The     .....       .....  Go Live...
DCN:<jdnewmil@dcn.davis.ca.us>        Basics: ##.#.       ##.#.  Live Go...
                                       Live:   OO#.. Dead: OO#..  Playing
Research Engineer (Solar/Batteries            O.O#.       #.O#.  with
/Software/Embedded Controllers)               .OO#.       .OO#.  rocks...1k
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