Re: Destructor not called with forward declaration instead of include

On 22 Apr, 03:43, internetpet <internet...@[EMAIL PROTECTED]
> 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
>      }

[snip]

> 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.
>
> Any idea why?

The type must be known for delete blah to be compilable.
Hence your code will not compile. Here's the error I got from gcc:

BigClazz.cpp: In destructor ‘BigClazz::~BigClazz()’:
BigClazz.cpp:5: warning: possible problem detected in invocation of
delete operator:
BigClazz.cpp:5: warning: invalid use of undefined type ‘struct Clazz’
BigClazz.h:1: warning: forward declaration of ‘struct Clazz’
BigClazz.cpp:5: note: neither the destructor nor the class-specific
operator delete will be called, even if they are declared when the
class is defined.

Says it all, I think.
You wouldn't be using a Micro$oft compiler by any chance?

-Andrew Marlow


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