On 22 Apr, 04:43, 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
> }
>
> 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.
>
> Any idea why?
Yes. According to [expr.delete]/5 in the standard (with my comments in
parens):
If the object being deleted has incomplete class type (in this case,
forward declared) at the point of deletion and the complete class has
a non-trivial destructor (you declared your own dtor, so it's non-
trivial) or a deallocation function, the behavior is undefined (which
usually means not calling the destructor in this case).
To fix this, simply #include "Clazz.h" in BigClazz.cpp, so that the
type is complete at the point of deletion.
--
DP
[ See http://www.gotw.ca/resources/clcm.htm
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