Re: Destructor not called with forward declaration instead of include
On Apr 21, 7:43 pm, internetpet <internet...@hotmail.com> wrote:
Say you have these files:
BigClazz.h
class Clazz; // Note the forward declaration only , no include
"Clazz.h"
class BigClazz
{
public:
BigClazz();
~BigClazz();
Clazz* pclazz;
};
BigClazz.cpp
#include "BigClazz.h"
BigClazz::BigClazz(){}
BigClazz::~BigClazz()
{
delete pclazz; // Here the destructor of of the Clazz object
will not be called
}
Clazz.h
class Clazz
{
public:
Clazz();
~Clazz();
};
Clazz.cpp
#include "Clazz.h"
Clazz::Clazz(){};
Clazz::~Clazz(){};
main.cpp
int main(int argc, char *argv[])
{
BigClazz* pVM = new BigClazz();
pVM->pclazz = new Clazz();
delete pVM;
}
If you run this you'll see that the Clazz destructor will not be
called when BigClazz does "delete pclazz;" in it's own destructor. But
if you replace the forward declaration in BigClazz (class Clazz;) with
an include
(#include "Clazz.h") then it works.
What I'm actually iffy on, is why you can compile code that deletes a
pointer to an incomplete type at all. This compiles with only a
warning about deleting a pointer to an incomplete type on VC9.
Can someone who is more of a language lawyer than I comment on if this
is permissible in the standard, and if so, why? It seems to me that
deleting an incomplete type would always be a mistake...
--
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