Re: ctor requires operator delete when using C++ exception handling

Alberto Ganesh Barbati <>
Fri, 2 Nov 2007 16:53:37 CST
vl106 ha scritto:

It seems that C++ exception handling (we currently don't use it
requires class to have operator delete available.


Therefore I declared but did not implement operator delete. Now
cannot call delete any more and they cannot delete the objects. They
will receive a linker error.

But this only works when exception handling is turned off. When turned
on I
(too) get the linker error:

unresolved external symbol "public: static void __cdecl C::operator
delete(void *)"
(??3C@@SAXPAX@Z) referenced in function

First, it's good to understand why operator delete is needed. In fact
it's not really needed by C::C(), it's needed by the evaluation of the
new-expression, that is:

   C* p = new C;

If, after the memory has been allocated, the initialization of the newly
created object fails with an exception, then the program shall attempt
to release the allocated memory before re-throwing the exception. This
is done by calling C::operator delete, that you declared.

Therefore, one workaround that avoid spurious friend declaration might
be the following:

1) declare both operator new and operator delete as private:

     void* operator new(size_t n) { return ::operator new(n); }
     void operator delete(void* p) { ::operator delete(p); }

(defining operator new is not strictly necessary, but it's bad style to
define one without the other)

2) declare a static factory method:

    static C* create_C(/* param here */) { return new C(/**/); }

That's it. You might still need some friendship in order to delete C
instances, but as there was no deletion code in your snippet, I can't
help your there.

In this framework, I would also declare all constructors as private, but
that's up to you.



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In Vigilance,
Daniel Joseph Min